High-dose Brachytherapy Boost With Stereostatic Body Radiation Therapy to Intermediate or Higher Risk Prostate Cancer

Currently the practice of minimizing monetary and human costs of therapy in the field of oncology is in vogue. As such, there has been heightened interest in the ability to decrease the total number and duration of radiation therapy treatments via brachytherapy and stereotactic body radiation therapy (SBRT). With this, the use of SBRT has been increasingly utilized for elective nodal irradiation (ENI) to treat patients with intermediate-risk prostate cancer or higher to improve biochemical progression free survival (bPFS). However, there is a dearth of studies assessing the efficacy and toxicity profile of these two modalities in combination. The objective of this phase I/II trial is to prospectively evaluate the toxicity and therapeutic efficacy of SBRT to prostate and pelvic lymph nodes in combination with high-dose-rate (HDR) brachytherapy to the prostate in patients with localized unfavorable-intermediate risk or higher disease. We hypothesize that this combination therapy will have an acceptable toxicity profile and that ENI via SBRT will provide improved bPFS compared to no nodal treatment and synonymous with conventional fractionation. The sample size will be 53 patients, with biopsy confirmed unfavorable-intermediate or higher risk prostate cancer and ≥ 15% probability of nodal involvement as determined by publicly available nomograms. Eligible patients will undergo ultrasound-guided HDR brachytherapy to the whole prostate to a dose of 15 Gy in 1 fractions followed by SBRT to a dose of 25 Gy in 5 fractions given every other day. Follow-up will assess toxicity and biochemical progression-free survival and subsequent comparison to historical results.