Stereotactic Pelvic Brachytherapy With HDR Boost for Dose Escalation in High Tier Intermediate and High Risk Prostate ca

Stereotactic Pelvic Brachytherapy With HDR Boost for Dose Escalation in High Tier Intermediate and High Risk Prostate Cancer (SPARE)

HDR brachytherapy in conjunction with pelvic SABR in high tier intermediate and high risk prostate cancer patients can provide a safe and effective means of radiotherapy dose escalation.

Utilizing multiparametric MRI to focally boost the dominant intraprostatic lesion during HDR brachytherapy is safe and feasible.

HDR brachytherapy:

Under general anesthetic, prostate will be implanted transperineally using up to 18 catheters. Three gold seed fudicials will also be implanted transperineally at base, midgland and apex forSABR treatment. Prostate will be contoured as Clinical Target Volume (CTV) on the transrectal ultrasound (TRUS) based ONCENTRA planning system. Rectum and urethra will be contoured as organs at risk. 15Gy will be prescribed to CTV as the MPD (minimal Peripheral Dose).

Treatment Delivery-SABR There will be a 2 week interval between HDR and SABR component to allow for normal tissue recovery and radiotherapy planning time. Daily image guidance will be performed using the implanted fiducials to calculate patient shifts to ensure proper positioning. Post-treatment images will be taken to estimate intrafraction motion.

Androgen Deprivation Therapy Twelve to 18 months of luteinizing-hormone releasing hormone agonists (LHRHa) will be used. Anti-androgen and neoadjuvant LHRHa can be used according to physician discretion

Follow-Up and Toxicity Assessment Time zero will be the start of radiotherapy. Baseline rectal and urinary function will be recorded using common toxicity criteria adverse effect (CTCAE v3.0) and Expanded prostate Cancer Index Composite (EPIC). CTCAE v3.0 and EPIC assessments will be done at weeks 3, 5 and 12 weeks. Bloodwork (PSA and testosterone), quality of life (EPIC) and late GI and GU toxicity evaluation (using the RTOG/EORTC Late Radiation Morbidity Scheme) will be performed every 6 months for the first 5 years.

Inclusion Criteria:

• Informed consent obtained
• Men >18 years
• Histologically confirmed prostate adenocarcinoma (centrally reviewed)
• High tier intermediate risk defined as :

Clinical stage T1-T2c AND PSA 10-20ng/ml AND {PSA>10ng/ml AND (T2b-2c Or Gleason 7)} OR Gleason 4+3

-High-risk prostate cancer, defined as at least one of: Clinical stage T3, OR Gl 8-10, OR PSA > 20 ng/mL

Inclusion Criteria:

• Prior pelvic radiotherapy
• Anticoagulation medication (if unsafe to discontinue for gold seed insertion)
• Diagnosis of bleeding diathesis
• Large prostate (>50cm3) on imaging
• No evidence of castrate resistance (defined as PSA < 3 ng/ml while testosterone is < 0.7 nmol/l. Patients could have been on combined androgen blockade but are excluded if this was started due to PSA progression.
• Definitive regional or distant metastatic disease on staging investigations.