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MRI-based 3D-4D brachytherapy in locally advanced cervical cancer

3D MRI-guided Brachytherapy

Richard Pötter, Prof., M.D.

Background:

The standard treatment of locally advanced cervical cancer is radio-chemotherapy including external beam radiotherapy (EBRT), brachytherapy (BT) and concomitant chemotherapy with weekly Cisplatin. While image based conformal EBRT is routinely used, prescription and reporting of BT is still based on specific dose points defined in 2D. Thus, for several decades the BT dose has most often been prescribed and reported to the Manchester point A defined according to different traditions.

Recently, a working group from GEC-ESTRO has published recommendations on contouring of tumour target and organs at risk (OAR) as well as on dose volume parameters to be reported for image guided BT in definitive radiotherapy for locally advanced cervical cancer. These recommendations are mainly derived from retrospective single institution experience with MRI based intracavitary BT. The major advantage of this technique is the possibility to conform the dose given by BT with regard to both volume (3D) and time (4D). Thus, by repetitive imaging performed before each BT implant it is possible adapt the dose given by BT to the anatomy of each individual patient taking into account not only the position of OAR but also the tumour regression which often is obtained by preceding EBRT and chemotherapy. Based on the experience collected so far, the image based BT approach is expected to have a major impact on the clinical outcome with a concomitant decrease in the rates of both local failure and morbidity.

Aims:

* To introduce MRI based 3D-4D BT in locally advanced cervical cancer in a multicenter setting within the frame of a prospective observational study.
* To establish a bench-mark for clinical outcome with image based BT in a large patient population with respect to local control, survival, morbidity and QoL
* To establish a reference material with regard to image based DVH parameters according to the guidelines from the GEC ESTRO working group.
* To correlate image based DVH parameters for CTV and for OAR with outcome
* To develop prognostic and predictive statistical models for clinical outcome including volumetric, dosimetric, clinical and biological risk factors
* To establish radiobiological parameter estimates that will allow a precise risk estimation in individual patients and aid in the development of new treatment protocols

A prospective observational multicenter study will be performed in patients with locally advanced cervical cancer considered to be potentially curable by definitive radio-(chemo) therapy. The patients will be divided and analyzed in three strata according to risk of recurrence:

1. Small tumours
2. Large tumours favourable response
3. Large tumours with unfavourable response to the initial radio-(chemo) therapy.

A clinical local failure has to be validated by MRI and topographically correlated to the MRI based BT targets (HR CTV and IR-CTV) and the dose volume parameters of the treatment plan. It has to be classified as "inside", "at the edge", "outside".

Major events with regard to morbidity have to be reported using 3D imaging information integrating e.g. clinical examination, endoscopy and MRI. The location of organ damage (i.e. fistula) has to be identified in 3D and a correlation to the dose volume parameters for the affected region should be investigated.

Specific Aims

* To assess prospectively outcome for disease (local control, survival), for morbidity and for QoL life applying appropriate clinical, imaging and QoL protocols.
* To test that there are three groups representing different risks of recurrence: small tumours; large tumours with favourable response; large tumours with unfavourable response to initial radio-(chemo)therapy.
* To correlate local control (survival) and dose volume parameters for GTV and CTV for the overall cohort and for the 3 different risk groups and to establish hazard ratios and dose effect curves for the primary tumour.
* To correlate outcome data and dose volume parameters for the different OAR (rectum, sigmoid, bladder) and to establish hazard ratios and dose effect curves for OAR.
* To correlate QoL outcome to morbidity outcome.
* To quantify the change in DVH parameters obtained by image guided dose optimization of BT in the individual patient.
* To compare volumetric data on GTV and CTV at diagnosis and during treatment and relate them to dose volume parameters within the 3 different risk groups of the overall patient cohort.
* To evaluate the indicators for quality assessment throughout the whole study period in order to define systematic and random variations for the different indicators (e.g. contouring, applicator reconstruction, dose volume assessment).
* To validate from clinical outcome data the radiobiological equivalence calculations used for assessing dose and volume parameters in gynaecological radiotherapy.
* To test if the GYN GEC ESTRO recommendations for BT in cervical cancer are feasible in a multi-centre setting.

An International Study on Magnetic Resonance Imaging (MRI)-Guided Brachytherapy in Locally Advanced Cervical Cancer

A International Study on MRI-guided Brachytherapy in Locally Advanced Cervical Cancer

Spots Global Cancer Trial Database for multicenter clinical study