Postop Hypofractionated Radiation Therapy and LHRH in Patients With Prostate Cancer

Overview

Prostate cancer is the second most common cancer among Canadian men of which approximately 20-30% present with high-risk tumour characteristic. Although surgery can be curative in patients evidencing pathological high-risk disease (extracapsular extension, seminal vesicle involvement, positive surgical margins), a large proportion will develop biochemical failure within years from the surgical procedure. The failure rate is even more pronounced in those patients that present with high prostate specific antigen (PSA) levels, pT3 disease, positive margins and Gleason score ≥8 with an estimated 75% failure rate at 10 years. Post-operative radiotherapy (RT) has been shown in three randomized trials to significantly decrease the biochemical failure rate and in one of the trials a survival benefit was also seen with the addition of post-operative RT and is considered by many investigators standard therapy in patients with pathological high-risks factors even in absence of biochemical failure.

Although RT is known to potentially eradicate microscopic disease localized in the prostatic bed, the current dilemma is whether to deliver RT in the adjuvant setting (defined as the use of RT post-prostatectomy to patients at a higher risk of recurrence because of adverse pathological features prior to evidence of disease recurrence (i.e., with an undetectable PSA) or to use it as an early salvage therapy (defined as the use of RT in patients with rising PSA but no evidence of metastatic disease). There are several institutional retrospective reports on the use of RT as salvage therapy but no randomized trial has ever been completed. The best evidence available, however, supports early salvage RT as the best strategy to be used to maximize results. Our own group has shown excellent results using this approach in patients with low and intermediate risk disease and is currently exploring this approach in patients with high-risk disease. Hypofractionated RT offers a more convenient shorter course of treatment, reduces health-costs and appears to be as effective and safe as conventionally fractionated regimens. This Phase 2 trial will study the potential role of hypofractionated in the post-operative setting in patients with high-risk features with the primary objective of assessing toxicity from this approach. The use of androgen deprivation therapy in combination with RT in the primary treatment for patients with intermediate or high-risk prostate cancer is well established. The use of androgen suppression in the post-operative setting has been less explored and its definitive role has not been fully explored. This is a phase II clinical trial to assess the feasibility and overall toxicity of adding one injection of neo-adjuvant hormonal therapy starting 12 weeks before plus Hypofractionated Radiotherapy for four weeks concurrently with another injection of luteinizing hormone-releasing hormone (LHRH) analog in patients with post-operative setting in patients with high-risk features.