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Low- or favourable intermediate-risk prostate cancer patients

Low dose rate (LDR) brachytherapy is a type of radiation treatment where doctor places the radioactive implants (seeds) inside patient's prostate gland and these seeds emits low dose radiation over a certain period of time. During low-dose-rate brachytherapy, a continuous low dose of radiation is released over time -from several hours to several days.

Low dose rate (LDR) brachytherapy

Robin Sachdeva, PhD

Lucas Mendez, MD, PhD

Lucas Mendez, MD

The purpose of this study is to develop and evaluate a Magnetic Resonance (MR) fusion 3D Ultrasound (US) guided Low dose rate (LDR) brachytherapy technique that significantly spares prostatic neurovascular bundles (a bundle of nerves and vessels that run beside the prostate) and penile bulb (base of the penis), while still trying to effectively treat the prostate cancer.

Low dose rate (LDR) brachytherapy is an excellent treatment strategy for patients with prostate confined cancers, achieving high curative rates. However, LDR brachytherapy has been linked with long-term erectile dysfunction (ED), with a broad range of reported incidence in the literature.

The pathophysiology associated with ED is complex and variable among different prostate cancer treatment strategies. In the post radical prostatectomy (RP) setting, ED is usually an immediate phenomenon and associated with neuropraxia caused by trauma and inflammation (Nandipati 2006). On the contrary, external beam radiotherapy (EBRT) related ED frequently occurs between 6-24 months and is believed to be vasculogenic in nature and caused by veno-vascular luminal occlusion (Mulhall et al. 2005) that culminates into fibrosis of the corporal tissue. In the post brachytherapy setting, seems plausible that a combination of both nerve and vascular damage are involved in the ED pathogenesis as erectile scores seem to reduce in the first months post implant (likely due to trauma) followed by a subsequent recovery and then, a gradual decline (Mabjeesh 2005).

Despite a more complex pathophysiology, rates of ED post LDR brachytherapy seem to be lower than post EBRT or RP treatment (Crook 2010, Putora 2015). This may be associated with a significantly lower degree of trauma to the surrounding healthy tissue compared with trauma caused by RP and a more conformal dose around the prostate when contrasted with EBRT. In this regard, brachytherapy delivers a lesser dose to important structures previously correlated with an erectile function such as the internal pudendal artery (IPA), penile bulb, corpus cavernosum and possibly the neurovascular bundle.

Currently, some strategies have been developed in an attempt to minimize ED post radiotherapy. In the POTEN-C clinical trial (NCT03525262), 120 patients are being randomized to stereotactic ablative radiotherapy with or without neurovascular sparing (neurovascular bundle, IPA and penile bulb/corpus carvenosum) with ED as the primary endpoint. Although the concept is intriguing, LDR brachytherapy has superior dose conformality and hence, a better chance to reduce radiation dose to the surrounding structures involved in the erectile function while still effectively treating the prostate cancer.

Prospective, single-arm clinical trial to enroll a total of 10 low- or favourable intermediate-risk prostate cancer patients.

Male only because this study trying to preserve the Penis erection in patients undergoing Radiation treatment for their prostate cancer.

Potency pReservation In Prostate cAncer Patients Treated With UltraSound-guided Low-dose Rate Brachytherapy

Acceptable dose distribution is defined as:

1. Target volume (Prostate, excluding a 5 mm expansion of the Neurovascular bundle) D90 ≥ 140 Gy
2. Contralateral neurovascular bundle median dose ≤ 50 Gy
3. Prostatic bulb D10 dose ≤ 50 Gy (Chasseray 2019)
4. Urethra D30 \< 130% of the prescription dose

The IIEF classifies the severity of ED into five categories stratified by score

* No ED.26-30
* Mild.22-25
* Mild to moderate.17-21
* Moderate.11-16
* Severe.6-10

Evaluate acute and long-term G3 or larger toxicity based on NCI-CTCAE 5.0 score system. Grade 1 to Grade 5. Higher the grade more severe is the toxicity.

Biochemical failure will be assessed according to the Phoenix criteria (nadir + 2.0ng/mL)

To assess the rate of biopsy-proven local recurrence

Lawson Health Research Institute

Behaviors and Mental Disorders

Quality of Life

Micronutrients

Anti-Infective Agents

All Drugs and Chemicals

Iodine

Cadexomer iodine

After completion of 46 Gy of external beam radiotherapy subjects will undergo a permanent seed radioactive implant to the prostate using iodine-125 seeds to deliver a dose of 110 Gy

Subjects in this arm will undergo an HDR implant to deliver 15 Gy to the prostate prior to commencing the external beam component of their treatment.

Juanita M Crook, MD

Optimal non surgical treatment of prostate cancer requires dose escalation which is frequently provided by adding a brachytherapy "boost" to a short course of external beam radiotherapy. The hypothesis in this randomized study is that a High Dose Rate (HDR) brachytherapy boost leads to equivalent or better Prostate Specific Antigen (PSA) recurrence-free survival when compared to a Low Dose Rate (LDR) brachytherapy boost and that it is associated with a more favorable toxicity profile and improved quality of life.

Men with intermediate or high risk prostate cancer who are technically suitable for prostate brachytherapy based on prostate size and voiding function and who are interested in this modality of treatment will be approached for randomization between either high dose rate (single 15 Gray) or low dose rate permanent seed implant (110 Gray) brachytherapy. Baseline International Prostate Symptom score, Quality of Life Assessment and International Index of Erectile Function will be recorded and then every 3 months for the first year and every 6 months to 3 years. Androgen deprivation treatment is allowed for 6 or 12 months.

Improving Quality of Life After Prostate Brachytherapy: a Comparison of HDR and LDR Brachytherapy

IMPROVING QUALITY OF LIFE AFTER OPTIMAL RADIOTHERAPY FOR INTERMEDIATE AND HIGH RISK PROSTATE CANCER: A Randomized Comparison of HDR Versus LDR BRACHYTHERAPY BOOST

regular PSA monitoring every 6 months to 3 years and then annually to determine PSA recurrence free survival

Quality of life will be measured through validated instruments including International Prostate Symptom Score (IPSS), the International Index of Erectile Function ((IEF), and the urinary, bowel and sexual domains of the Expanded Prostate Cancer Index Composite (EPIC). IPSS has 7 questions related to voiding symptoms, each scored 0-5, with a higher score indicating worse symptoms. IIEF has 5 questions, each scored 0-5 with a higher score indicating better function. EPIC has several questions for each domain with an overall higher score associated with better QoL in that domain.

Quality of Life will be assessed to 5 years using the validated instruments International Prostate Symptom Score, International Index Erectile Function and EPIC

Study title	NCT ID	Conditions	Interventions	Eligibility	Organization	Link
Potency pReservation In Prostate cAncer Patients Treated With UltraSound-guided Low-dose Rate Brachytherapy	NCT04718987	Prostate Cancer	Low dose rate (...	18 Years - 75 Years	Lawson Health Research Institute
Improving Quality of Life After Prostate Brachytherapy: a Comparison of HDR and LDR Brachytherapy	NCT01936883	Prostate Cancer	HDR LDR	45 Years - 80 Years	British Columbia Cancer Agency

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