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Gabapentin

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The study cohort from which cases and controls are drawn is all subjects in the United Kingdom (UK) General Practice Research Database (GPRD) 1993-2008. Each member of the UK population is registered with a General Practice, which centralizes the medical information not only from the general practitioners themselves but also from specialist referrals and hospital attendances. Over 487 General Practices contribute data to the GPRD. Entry into the study cohort begins Jan 1, 1993 for all those who are registered in GPRD before that time, and at the time of registration if later than Jan 1, 1993. Subjects are excluded from the GPRD cohort if they have a cancer diagnosis or a history of cancer prior to the cohort entry date.

The exposure of interest is gabapentin use as defined by prescriptions recorded by the GPRD general practitioner (British National Formulry codes). Data on prescriptions for gabapentin will be extracted for each case and control from entry into the study cohort up to two years prior to the index date (the exposure window). A two year lagged exposure is incorporated to account for latency between cancer onset and GPRD diagnosis, and for protopathic bias (gabapentin prescription for initial pain symptoms of undiagnosed cancer). Gabapentin exposure will be parameterized as follows: (1) Ever versus never exposed; (2) Number of prescriptions; (3) Duration of exposure; and (4) Cumulative dose.

Gabapentin prescriptions

GSK Clinical Trials

High doses of gabapentin are associated with pancreatic acinar cell tumors in rats, but there has been no post marketing pancreatic carcinogenicity signal with gabapentin as reported by spontaneous reports in AERS or in the published literature. In a published case-control screening study of the association of gabapentin with 55 cancers, the only cancer that met the screening criteria for possibly increased cancer risk with gabapentin exposure was renal (including renal pelvis) cancer. This association was judged to be likely due to or substantially accentuated by confounding by cigarette smoking, hypertension, and lifestyle (Cancer Causes Control 2009;20:1821-1835).

The relationship between gabapentin exposure and pancreatic cancer and renal cancer is studied in NCT01138124, and supplemental analyses for these cancers are performed in the current study. The FDA recommended GSK also study the relationship between gabapentin and all-cancer sites, as well as cancer at the following specific sites: 1) stomach, 2) anus, anal canal, and anorectum, 3) lung and bronchus, 4) bones and joints, 5) breast, 6) penis, 7) urinary bladder, and 8) other nervous system.

The primary objective of this study is to determine whether exposure to gabapentin is associated with an increased risk of developing all-cancer, and these specific cancers in the United Kingdom (UK) General Practice Research Database (GPRD). Each member of the UK population is registered with a General Practice, which centralizes the medical information not only from the general practitioners themselves but also from specialist referrals and hospital attendances. Over 487 General Practices contribute data to the GPRD.

The study cohort from which cases and controls are drawn is all subjects in the GPRD 1993-2008. Gabapentin was approved in the UK in May 1993. Entry into the study cohort begins Jan 1, 1993 for all those who are registered in GPRD before that time, and at the time of registration if later than Jan 1, 1993. Subjects are excluded from the GPRD cohort if they have a cancer diagnosis or a history of cancer prior to the cohort entry date. Patients with a first diagnosis of the respective cancer 1995-2008 are risk set matched with up to 10 controls within the same General Practice for age at cohort entry (within two years), sex, and year of entry into the study cohort (within one year). For cases, the index date is the date of first diagnosis of the respective cancer. The index date for controls is set as the date at which the follow-up time from cohort entry is the same as the case. The index date is chosen so as to give the control equal follow-up time to that of the case for ascertainment of use of gabapentin. Cases and controls will be required to have at least 2 years of follow-up in the study cohort before their index date. Cases must have no history of any other cancer diagnosis prior to the index date. Controls are required to be free of cancer diagnosis in the database up to the control's index date.

Data on gabapentin prescriptions are obtained for cases and controls from study cohort entry to the index date. Gabapentin exposure will be assessed as ever/never, number of prescriptions, cumulative dose, and cumulative duration, with a 2 year lag period incorporated to control for protopathic bias (gabapentin prescription for initial pain symptoms of undiagnosed cancer) and latency (time between cancer onset and specific GPRD cancer diagnosis).

Crude and adjusted odds ratios and 95% confidence intervals (CI) will be produced from conditional logistic regression models, with additional analyses evaluating for dose-response. Covariates include indications for gabapentin use and risk factors for each cancer.

Actual number of patients may be less, as it is possible for a patient to be represented in more than one of the 22 arms (See "Participant Flow: Overall Study" Table) because of the risk set sampling.

Cancer in Patients With Gabapentin (GPRD)

Risk of Cancer in Patients Exposed to Gabapentin in the GPRD

Incidence of all cancers. Gabapentin Exposure Description: Without 2 year lag = Gabapentin prescription from cohort entry to index date. With 2 year lag = Gabapentin prescription from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer).

Incidence of all cancers. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date. Tertile's with 2 year lag: Tertile 1 (1-2 prescriptions), Tertile 2 (3-7 prescriptions), Tertile 3 (8-298 prescriptions). Tertiles without 2 year lag: Tertile 1 (1-2 prescriptions), Tertile 2 (3-7 prescriptions), and Tertile 3 (8-388 prescriptions).

Incidence of all cancers. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date. Tertile's with 2 year lag: Tertile 1 (0.01 - 1.38 months), Tertile 2 (1.39 - 5.56 months), and Tertile 3 (5.57 - 105.82 months). Tertile's without 2 year lag: Tertile 1 (0.01 - 1.38 months), Tertile 2 (1.39 - 5.72 months), and Tertile 3 (5.73 - 123.70 months).

Incidence of all cancers. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date.

Incidence of all cancers. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date. Tertile's with 2 year lag: Tertile 1 (0.1 - 30.0 grams), Tertile 2 (30.1 - 189.0 grams), and Tertile 3 (189.1 - 9600.0 grams). Tertile's without 2 year lag: Tertile 1 (0.1 - 30.0 grams), Tertile 2 (30.1 - 189.0 grams), and Tertile 3 (189.1 - 11610.0 grams).

Incident stomach cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin prescription from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin prescription from cohort entry to index date.

Incident stomach cancer. Gabapentin (Gaba.) Exposure Description: With 2 year (yr) lag=Gaba. exposure from cohort entry to 2 yr prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 yr lag=Gaba. exposure from cohort entry to index date. Tertiles (T) with 2 yr lag: T 1 (1-2 prescriptions \[prescrip\]), T 2 (3-7 prescrip), T 3 (8-298 prescrip). Tertiles without 2 yr lag: T 1 (1-2 prescrip), T 2 (3-7 prescrip), and T 3 (8-388 prescrip). Inestimable OR and 95% CI when no gaba.-exposed cancer cases or controls at the exposure level.

Incident stomach cancer. Gabapentin (Gaba.) Exposure Description: With 2 year (yr) lag=Gaba. exposure from cohort entry to 2 yr prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 yr lag=Gaba. exposure from cohort entry to index date. Tertiles (T) with 2 yr lag: T 1 (0.01-1.38 months \[mo.\]), T 2 (1.3-5.56 mo.), and T 3 (5.57-105.82 mo.). Tertiles without 2 yr lag: T 1 (0.01-1.38 m.), T 2 (1.39-5.72 mo.), and T 3 (5.73-123.70 mo.). Inestimable OR and 95% CI when no gaba.-exposed cancer cases or controls at the exposure level.

Incident stomach cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date.

Incident stomach cancer. Gabapentin (Gaba.) Exposure Description: With 2 year (yr) lag=Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 yr lag=Gaba. exposure from cohort entry to index date. Tertiles (T) with 2 yr lag: T 1 (0.1-30.0 grams \[g\]), T 2 (30.1-189.0 g), and T 3 (189.1-9600.0 g). Tertiles without 2 yr lag: T 1 (0.1-30.0 g), T 2 (30.1-189.0 g), and T 3 (189.1-11610.0 g). Inestimable OR and 95% CI when no gaba.-exposed cancer cases or controls at the exposure level.

Incident Anal cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin prescription from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin prescription from cohort entry to index date.

Incident anal cancer. Gabapentin (Gaba.) Exposure Description: With 2 year (yr) lag=Gaba. exposure from cohort entry to 2 yr prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 yr lag=Gaba. exposure from cohort entry to index date. Tertiles (T) with 2 yr lag: T 1 (1-2 prescriptions \[prescrip.\]), T 2 (3-7 prescrip.), T 3 (8-298 prescrip.). Tertiles without 2 yr lag: T 1 (1-2 prescrip.), T 2 (3-7 prescrip.), and T 3 (8-388 prescrip.). Inestimable OR and 95% CI when no gaba.-exposed cancer cases or controls at the exposure level.

Incident anal cancer. Gabapentin (Gaba.) Exposure Description: With 2 year (yr) lag=Gaba. exposure from cohort entry to 2 yr prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 yr lag=Gaba. exposure from cohort entry to index date. Tertiles (T) with 2 yr lag: T 1 (0.01-1.38 months \[mo.\]), T 2 (1.39-5.56 mo.), and T 3 (5.57 -105.82 mo.). Tertiles without 2 yr lag: T 1 (0.01-1.38 mo.), T 2 (1.39-5.72 mo.), and T 3 (5.73-123.70 mo.). Inestimable OR and 95% CI when no gaba.-exposed cancer cases or controls at the exposure level.

Incident anal cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date.

Incident anal cancer. Gabapentin (Gaba.) Exposure Description: With 2 yr lag=Gaba. exposure from cohort entry to 2 yr prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 yr lag=Gaba. exposure from cohort entry to index date. Tertiles (T) with 2 yr lag: T 1 (0.1-30.0 grams \[g\]), T 2 (30.1-189.0 g), and T 3 (189.1-9600.0 g). Tertiles without 2 yr lag: T 1 (0.1-30.0 g), T 2 (30.1-189.0 g), and T 3 (189.1-11610.0 g). Inestimable OR and 95% CI when no gaba.-exposed cancer cases or controls at the exposure level.

Incident lung cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin prescription from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin prescription from cohort entry to index date.

Incident lung cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date. Tertile's with 2 year lag: Tertile 1 (1-2 prescriptions), Tertile 2 (3-7 prescriptions), Tertile 3 (8-298 prescriptions). Tertiles without 2 year lag: Tertile 1 (1-2 prescriptions), Tertile 2 (3-7 prescriptions), and Tertile 3 (8-388 prescriptions).

Incident lung cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date. Tertile's with 2 year lag: Tertile 1 (0.01 - 1.38 months), Tertile 2 (1.39 - 5.56 months), and Tertile 3 (5.57 - 105.82 months). Tertile's without 2 year lag: Tertile 1 (0.01 - 1.38 months), Tertile 2 (1.39 - 5.72 months), and Tertile 3 (5.73 - 123.70 months).

Incident lung cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date.

Incident lung cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date. Tertile's with 2 year lag: Tertile 1 (0.1 - 30.0 grams), Tertile 2 (30.1 - 189.0 grams), and Tertile 3 (189.1 - 9600.0 grams). Tertile's without 2 year lag: Tertile 1 (0.1 - 30.0 grams), Tertile 2 (30.1 - 189.0 grams), and Tertile 3 (189.1 - 11610.0 grams).

Incident bone/joint cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin prescription from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin prescription from cohort entry to index date. Inestimable OR and 95% CI when no gabapentin-exposed cancer cases or no gabapentin-exposed controls at the exposure level.

Incident bone/joint cancer. Gabapentin (Gaba.) Exposure Description: With 2 year (yr) lag=Gaba. exposure from cohort entry to 2 yr prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 yr lag=Gaba. exposure from cohort entry to index date. Tertiles (T) with 2 yr lag: T 1 (1-2 prescriptions \[prescrip.\]), T 2 (3-7 prescrip.), T 3 (8-298 prescrip.). Tertiles without 2 yr lag: T 1 (1-2 prescrip.), T 2 (3-7 prescrip.), and T 3 (8-388 prescrip.). Inestimable OR and 95% CI when no gaba.-exposed cases or controls at the exposure level.

Incident bone/joint cancer. Gabapentin (Gaba.) Exposure Description: With 2 year (yr) lag=Gaba. exposure from cohort entry to 2 yr prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 yr lag=Gaba. exposure from cohort entry to index date. Tertiles (T) with 2 yr lag: T 1 (0.01-1.38 months \[mo.\]), T 2 (1.39-5.56 mo.), and T 3 (5.57-105.82 mo.). Tertiles without 2 yr lag: T 1 (0.01-1.38 mo.), T 2 (1.39-5.72 mo.), and T 3 (5.73-123.70 mo.). Inestimable OR and 95% CI when no gaba.-exposed cases or controls at the exposure level.

Incident bone/joint cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date.

Incident bone/joint cancer. Gabapentin (Gaba.) Exposure Description: With 2 year (yr) lag=Gaba. exposure from cohort entry to 2 yr prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 yr lag=Gaba. exposure from cohort entry to index date. Tertiles (T) with 2 yr lag: T 1 (0.1-30.0 grams \[g\]), T 2 (30.1-189.0 g), and T 3 (189.1-9600.0 g). Tertiles without 2 yr lag: T 1 (0.1-30.0 g), T 2 (30.1-189.0 g), and T 3 (189.1-11610.0 g). Inestimable OR and 95% CI when no gaba.-exposed cancer cases or controls at the exposure level.

Incident breast cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin prescription from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin prescription from cohort entry to index date.

Incident breast cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date. Tertile's with 2 year lag: Tertile 1 (1-2 prescriptions), Tertile 2 (3-7 prescriptions), Tertile 3 (8-298 prescriptions). Tertiles without 2 year lag: Tertile 1 (1-2 prescriptions), Tertile 2 (3-7 prescriptions), and Tertile 3 (8-388 prescriptions).

Incident breast cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date. Tertile's with 2 year lag: Tertile 1 (0.01 - 1.38 months), Tertile 2 (1.39 - 5.56 months), and Tertile 3 (5.57 - 105.82 months). Tertile's without 2 year lag: Tertile 1 (0.01 - 1.38 months), Tertile 2 (1.39 - 5.72 months), and Tertile 3 (5.73 - 123.70 months).

Incident breast cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date.

Incident breast cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date. Tertile's with 2 year lag: Tertile 1 (0.1 - 30.0 grams), Tertile 2 (30.1 - 189.0 grams), and Tertile 3 (189.1 - 9600.0 grams). Tertile's without 2 year lag: Tertile 1 (0.1 - 30.0 grams), Tertile 2 (30.1 - 189.0 grams), and Tertile 3 (189.1 - 11610.0 grams).

Incident penile cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin prescription from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin prescription from cohort entry to index date.

Incident penile cancer. Gabapentin (Gaba.) Exposure Description: With 2 year (yr) lag=Gaba. exposure from cohort entry to 2 yr prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 yr lag=Gaba. exposure from cohort entry to index date. Tertiles (T) with 2 yr lag: T 1 (1-2 prescriptions \[prescrip.\]), T 2 (3-7 prescrip.), T 3 (8-298 prescrip.). Tertiles without 2 yr lag: T 1 (1-2 prescrip.), T 2 (3-7 prescrip.), and T 3 (8-388 prescrip.). Inestimable OR/95% CI when no gaba.-exposed cancer cases or controls at the exposure level.

Incident penile cancer. Gabapentin (Gaba.) Exposure Description: With 2 year (yr) lag=Gaba. exposure from cohort entry to 2 yr prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 yr lag=Gaba. exposure from cohort entry to index date. Tertiles (T) with 2 yr lag: T 1 (0.01-1.38 months \[mo.\]), T 2 (1.39-5.56 mo.), and T 3 (5.57-105.82 mo.). Tertiles without 2 yr lag: T 1 (0.01-1.38 mo.), T 2 (1.39-5.72 mo.), and T 3 (5.73-123.70 mo.). Inestimable OR and 95% CI when no gaba.-exposed cancer cases or controls at the exposure level.

Incident penile cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date.

Incident penile cancer. Gabapentin (Gaba.) Exposure Description: With 2 year (yr) lag=Gaba. exposure from cohort entry to 2 yr prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 yr lag=Gaba. exposure from cohort entry to index date. Tertiles (T) with 2 yr lag: T 1 (0.1-30.0 grams \[g\]), T 2 (30.1-189.0 g), and T 3 (189.1-9600.0 g). Tertiles without 2 yr lag: T 1 (0.1-30.0 g), T 2 (30.1-189.0 g), and T 3 (189.1-11610.0 g). Inestimable OR and 95% CI when no gaba.-exposed cancer cases or controls at the exposure level.

Incident bladder cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin prescription from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin prescription from cohort entry to index date.

Incident bladder cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date. Tertile's with 2 year lag: Tertile 1 (1-2 prescriptions), Tertile 2 (3-7 prescriptions), Tertile 3 (8-298 prescriptions). Tertiles without 2 year lag: Tertile 1 (1-2 prescriptions), Tertile 2 (3-7 prescriptions), and Tertile 3 (8-388 prescriptions).

Incident bladder cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date. Tertile's with 2 year lag: Tertile 1 (0.01 - 1.38 months), Tertile 2 (1.39 - 5.56 months), and Tertile 3 (5.57 - 105.82 months). Tertile's without 2 year lag: Tertile 1 (0.01 - 1.38 months), Tertile 2 (1.39 - 5.72 months), and Tertile 3 (5.73 - 123.70 months).

Incident bladder cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date.

Incident bladder cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date. Tertile's with 2 year lag: Tertile 1 (0.1 - 30.0 grams), Tertile 2 (30.1 - 189.0 grams), and Tertile 3 (189.1 - 9600.0 grams). Tertile's without 2 year lag: Tertile 1 (0.1 - 30.0 grams), Tertile 2 (30.1 - 189.0 grams), and Tertile 3 (189.1 - 11610.0 grams).

Incident other nervous system cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin prescription from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin prescription from cohort entry to index date. Inestimable OR and 95% CI when no gabapentin-exposed cancer cases or no gabapentin-exposed controls at the exposure level.

Incident ONS cancer. Gabapentin (Gaba.) Exposure Description: With 2 year (yr) lag=Gaba. exposure from cohort entry to 2 yr prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 yr lag=Gaba. exposure from cohort entry to index date. Tertiles (T) with 2 yr lag: T 1 (1-2 prescriptions \[prescrip.\]), T 2 (3-7 prescrip.), T 3 (8-298 prescrip.). Tertiles without 2 yr lag: T 1 (1-2 prescrip.), T 2 (3-7 prescrip.), and T 3 (8-388 prescrip.). Inestimable OR and 95% CI when no gaba.-exposed cancer cases or controls at the exposure level.

Incident ONS cancer. Gabapentin (Gaba.) Exposure Description: With 2 yr lag=Gaba. exposure from cohort entry to 2 yr prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 yr lag=Gaba. exposure from cohort entry to index date. Tertiles (T) with 2 yr lag: T 1 (0.01-1.38 months \[mo.\]), T 2 (1.39-5.56 mo.), and T 3 (5.57-105.82 mo.). Tertiles without 2 yr lag: T 1 (0.01-1.38 mo.), T 2 (1.39-5.72 mo.), and T 3 (5.73-123.70 mo.). Inestimable OR and 95% CI when no gaba.-exposed cancer cases or controls at the exposure level.

Incident other nervous system cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date.

Incident ONS cancer. Gabapentin (Gaba.) Exposure Description: With 2 year (yr) lag=Gaba. exposure from cohort entry to 2 yr prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 yr lag=Gaba. exposure from cohort entry to index date. Tertiles (T) with 2 yr lag: T 1 (0.1-30.0 grams \[g\]), T 2 (30.1-189.0 g), and T 3 (189.1-9600.0 g). Tertiles without 2 yr lag: T 1 (0.1-30.0 g), T 2 (30.1-189.0 g), and T 3 (189.1-11610.0 g). Inestimable OR and 95% CI when no gaba.-exposed cancer cases or controls at the exposure level.

Incident pancreatic cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin prescription from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin prescription from cohort entry to index date.

Incident pancreatic cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date. Tertile's with 2 year lag: Tertile 1 (1-2 prescriptions), Tertile 2 (3-7 prescriptions), Tertile 3 (8-298 prescriptions). Tertiles without 2 year lag: Tertile 1 (1-2 prescriptions), Tertile 2 (3-7 prescriptions), and Tertile 3 (8-388 prescriptions).

Incident pancreatic cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date. Tertile's with 2 year lag: Tertile 1 (0.01 - 1.38 months), Tertile 2 (1.39 - 5.56 months), and Tertile 3 (5.57 - 105.82 months). Tertile's without 2 year lag: Tertile 1 (0.01 - 1.38 months), Tertile 2 (1.39 - 5.72 months), and Tertile 3 (5.73 - 123.70 months).

Incident pancreatic cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date.

Incident pancreatic cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date. Tertile's with 2 year lag: Tertile 1 (0.1 - 30.0 grams), Tertile 2 (30.1 - 189.0 grams), and Tertile 3 (189.1 - 9600.0 grams). Tertile's without 2 year lag: Tertile 1 (0.1 - 30.0 grams), Tertile 2 (30.1 - 189.0 grams), and Tertile 3 (189.1 - 11610.0 grams).

Incident renal cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin prescription from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin prescription from cohort entry to index date.

Incident renal cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date. Tertile's with 2 year lag: Tertile 1 (1-2 prescriptions), Tertile 2 (3-7 prescriptions), Tertile 3 (8-298 prescriptions). Tertiles without 2 year lag: Tertile 1 (1-2 prescriptions), Tertile 2 (3-7 prescriptions), and Tertile 3 (8-388 prescriptions).

Incident renal cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date. Tertile's with 2 year lag: Tertile 1 (0.01 - 1.38 months), Tertile 2 (1.39 - 5.56 months), and Tertile 3 (5.57 - 105.82 months). Tertile's without 2 year lag: Tertile 1 (0.01 - 1.38 months), Tertile 2 (1.39 - 5.72 months), and Tertile 3 (5.73 - 123.70 months).

Incident renal cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date.

Incident renal cancer. Gabapentin Exposure Description: With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Without 2 year lag = Gabapentin exposure from cohort entry to index date. Tertile's with 2 year lag: Tertile 1 (0.1 - 30.0 grams), Tertile 2 (30.1 - 189.0 grams), and Tertile 3 (189.1 - 9600.0 grams). Tertile's without 2 year lag: Tertile 1 (0.1 - 30.0 grams), Tertile 2 (30.1 - 189.0 grams), and Tertile 3 (189.1 - 11610.0 grams).

GlaxoSmithKline

This is a retrospective study of pre-existing medical record and/or health insurance claims data; all data are de-identified, and thus no assessments of Serious or Non-serious Adverse Events are possible.

Incidence of all cancers defined as first time incident cancer diagnosis (READ/Oxford Medical Information System \[OXMIS\] codes) in the General Practice Research Database (GPRD) study cohort. Entry into the study cohort began January 1, 1993, or at the time of GPRD registration if after January 1, 1993. Follow-up ended December 31, 2008, or earlier if the respective cancer was diagnosed or if the participant left the GPRD for any reason including death. Participants with a prior history of cancer were excluded.

All-Cancer: Cases

Cancer cases were risk set matched with up to 10 controls for sex, age at GPRD study cohort entry (within two years), calendar year of cohort entry (within one year), and General Practice site. The index date for controls was set as the date at which the follow-up time from cohort entry was the same as the case. The index date was chosen so as to give the control equal follow-up time to that of the case for ascertainment of use of gabapentin. Participants with a history of cancer prior to the index date were excluded as controls.

All-Cancer: Controls

Incidence of stomach cancer defined as first time incident cancer diagnosis (READ/Oxford Medical Information System \[OXMIS\] codes) in the General Practice Research Database (GPRD) study cohort. Entry into the study cohort began January 1, 1993, or at the time of GPRD registration if after January 1, 1993. Follow-up ended December 31, 2008, or earlier if the respective cancer was diagnosed or if the participant left the GPRD for any reason including death. Participants with a prior history of cancer were excluded.

Stomach Cancer: Cases

Stomach Cancer: Controls

Incidence of anal cancer defined as first time incident cancer diagnosis (READ/Oxford Medical Information System \[OXMIS\] codes) in the General Practice Research Database (GPRD) study cohort. Entry into the study cohort began January 1, 1993, or at the time of GPRD registration if after January 1, 1993. Follow-up ended December 31, 2008, or earlier if the respective cancer was diagnosed or if the participant left the GPRD for any reason including death. Participants with a prior history of cancer were excluded.

Anal Cancer: Cases

Anal Cancer: Controls

Incidence of lung cancer defined as first time incident cancer diagnosis (READ/Oxford Medical Information System \[OXMIS\] codes) in the General Practice Research Database (GPRD) study cohort. Entry into the study cohort began January 1, 1993, or at the time of GPRD registration if after January 1, 1993. Follow-up ended December 31, 2008, or earlier if the respective cancer was diagnosed or if the participant left the GPRD for any reason including death. Participants with a prior history of cancer were excluded.

Lung Cancer: Cases

Lung Cancer: Controls

Incidence of bone/joint cancer defined as first time incident cancer diagnosis (READ/Oxford Medical Information System \[OXMIS\] codes) in the General Practice Research Database (GPRD) study cohort. Entry into the study cohort began January 1, 1993, or at the time of GPRD registration if after January 1, 1993. Follow-up ended December 31, 2008, or earlier if the respective cancer was diagnosed or if the participant left the GPRD for any reason including death. Participants with a prior history of cancer were excluded.

Bone/Joint Cancer: Cases

Bone/Joint Cancer: Controls

Incidence of breast cancer defined as first time incident cancer diagnosis (READ/Oxford Medical Information System \[OXMIS\] codes) in the General Practice Research Database (GPRD) study cohort. Entry into the study cohort began January 1, 1993, or at the time of GPRD registration if after January 1, 1993. Follow-up ended December 31, 2008, or earlier if the respective cancer was diagnosed or if the participant left the GPRD for any reason including death. Participants with a prior history of cancer were excluded.

Breast Cancer: Cases

Breast Cancer: Controls

Incidence of penile cancer defined as first time incident cancer diagnosis (READ/Oxford Medical Information System \[OXMIS\] codes) in the General Practice Research Database (GPRD) study cohort. Entry into the study cohort began January 1, 1993, or at the time of GPRD registration if after January 1, 1993. Follow-up ended December 31, 2008, or earlier if the respective cancer was diagnosed or if the participant left the GPRD for any reason including death. Participants with a prior history of cancer were excluded.

Penile Cancer: Cases

Penile Cancer: Controls

Incidence of bladder cancer defined as first time incident cancer diagnosis (READ/Oxford Medical Information System \[OXMIS\] codes) in the General Practice Research Database (GPRD) study cohort. Entry into the study cohort began January 1, 1993, or at the time of GPRD registration if after January 1, 1993. Follow-up ended December 31, 2008, or earlier if the respective cancer was diagnosed or if the participant left the GPRD for any reason including death. Participants with a prior history of cancer were excluded.

Bladder Cancer: Cases

Bladder Cancer: Controls

Incidence of other nervous system cancer defined as first time incident cancer diagnosis (READ/Oxford Medical Information System \[OXMIS\] codes) in the General Practice Research Database (GPRD) study cohort. Entry into the study cohort began January 1, 1993, or at the time of GPRD registration if after January 1, 1993. Follow-up ended December 31, 2008, or earlier if the respective cancer was diagnosed or if the participant left the GPRD for any reason including death. Participants with a prior history of cancer were excluded.

Other Nervous System Cancer: Cases

Other Nervous System Cancer: Controls

Incidence of pancreatic cancer defined as first time incident cancer diagnosis (READ/Oxford Medical Information System \[OXMIS\] codes) in the General Practice Research Database (GPRD) study cohort. Entry into the study cohort began January 1, 1993, or at the time of GPRD registration if after January 1, 1993. Follow-up ended December 31, 2008, or earlier if the respective cancer was diagnosed or if the participant left the GPRD for any reason including death. Participants with a prior history of cancer were excluded.

Pancreatic Cancer: Cases

Pancreatic Cancer: Controls

Incidence of renal cancer defined as first time incident cancer diagnosis (READ/Oxford Medical Information System \[OXMIS\] codes) in the General Practice Research Database (GPRD) study cohort. Entry into the study cohort began January 1, 1993, or at the time of GPRD registration if after January 1, 1993. Follow-up ended December 31, 2008, or earlier if the respective cancer was diagnosed or if the participant left the GPRD for any reason including death. Participants with a prior history of cancer were excluded.

Renal Cancer: Cases

Renal Cancer: Controls

Total

< 40 years

40-49 years

50-59 years

60-69 years

70-79 years

80+ years

Age, Customized

Sex: Female, Male

0-1 years

2-3 years

4-5 years

6-7 years

8+ years

Entry into the GPRD study cohort began January 1, 1993, or at the time of GPRD registration if after January 1, 1993. Participants were required to have at least 2 years of follow-up prior to the index date.

Number of participants with the indicated duration of follow-up from registration to index date

Number of participants with the indicated duration of follow-up from cohort entry to index date

BMI: < 18.5 kg/m^2

BMI: 18.5 to 24.99 kg/m^2

BMI: 25 to 29.99 kg/m^2

BMI: 30 kg/m^2 or greater

BMI: Missing

BMI is calculated as weight in kilograms (kg) (closest to cohort entry date, up to one year prior to index date) divided by height in meters squared (m\^2) (one year or longer prior to index date).

Spots Global Cancer Trial Database for bone and joint cancer