Disease and Toxicity Outcomes after Salvage Radiotherapy (SRT) for Biochemically Recurrent Prostate Cancer (PC) for Patients Enrolled in a Phase II, Open Label Trial Investigating Neoadjuvant Chemohormonal Therapy Followed by Radical Prostatectomy (RP)

Abstract

Men with metastatic hormone sensitive prostate cancer have improved progression free and overall survival (PFS/OS) when treated with docetaxel and androgen deprivation therapy (ADT). Our institution conducted a phase II trial (UW17009) investigating the addition of three cycles of neoadjuvant docetaxel and ADT to RP in men with high-risk prostate cancer. Here we report toxicity and freedom from biochemical recurrence (FFBCR) for patients treated with SRT following participation in this trial. Between January 17, 2018 and August 10, 2021, 28 patients enrolled on UW17009. Patients who had a recurrence and received SRT were identified. Toxicity was assessed using modified LENT (Late Effects of Normal Tissues)/RTOG (Radiation Therapy Oncology Group) criteria, and time to recurrence following SRT was determined for each patient. Additionally, the months of ADT received by each patient was recorded. FFBCR was then determined for this cohort using the method of Kaplan and Meier. Of 28 patients enrolled on UW17009, 20 (71%) had BCR after RP. Of these, 19 received SRT, representing 68% of the patients enrolled on the trial. The rates of acute grade 1 and grade 2 GU toxicity with SRT were 37% (7) and 53% (10), respectively. The rates of acute grade 1 and grade 2 GI toxicity with SRT were 32% (6) and 37% (7), respectively. On patient experienced a grade 4 genitourinary toxicity during SRT. There were no acute grade 3 or grade 5 toxicities. The rates of late grade 1 and grade 2 GU toxicity were 16% (3) and 11% (2), respectively. The rates of late grade 1 and grade 2 GI toxicity were 11% (2) and 5% (1), respectively. There was 1 (5%) late grade 3 GU toxicity. There were no late grade 3-5 GI toxicities, or late grade 4-5 GU toxicities. The average duration of ADT after prostatectomy was 15 months (range: 0-37 months). According to the method of Kaplan and Meier, mean FFBCR after SRT was 34.0 months at a median of 37.8 months. Median FFBCR had not yet been reached. At the time of analysis, 13 patients remained free from biochemical recurrence after SRT. Rates of biochemical recurrence and SRT following neoadjuvant docetaxel and ADT and then RP were consistent with historical data, as was the rate of successful SRT. Toxicities were also consistent with historical data, though there was notably one acute grade 4 GU toxicity.