Main Session
Sep
30
PQA 08 - Gastrointestinal Cancer, Nonmalignant Disease, Palliative Care
3517 - Deep and Durable Prostate-Specific Antigen Response Following Comprehensive Involved Site Radiotherapy for Prostate Cancer Oligometastases
Presenter(s)
Megha Schmalzle, BS - New York Institute of Technology College of Osteopathic Medicine, Old Westbury, NY
M. Schmalzle1,2, R. Radigan1,2, C. Atalla3, E. Sygaco4, S. Hoque4, and J. Kao1,2; 1Good Samaritan University Hospital, Department of Radiation Oncology, West Islip, NY, 2New York Institute of Technology College of Osteopathic Medicine, Old Westbury, NY, 3Good Samaritan University Hospital, Department of Urology, Bay Shore, NY, 4The Cancer Institute at Good Samaritan Hospital, West Islip, NY
Purpose/Objective(s):
Achieving undetectable PSA has been correlated with improved clinical outcomes for patients with metastatic prostate cancer. Comprehensive involved site radiotherapy (ISRT) consisting of local therapy to the prostate and radiation to all visible bone and lymph node metastases has emerged as a method of treatment intensification for prostate cancer oligometastases. The purpose of this study is to evaluate the frequency and predictors of undetectable PSA in patients who received radiotherapy for oligometastases.Materials/Methods:
The study population included 35 consecutive men with oligometastastic prostate cancer treated by a single radiation oncologist from 2014 to 2024. All men were treated with comprehensive ISRT with a median follow-up of 1.9 years (IQR 1.1-4.0). Baseline characteristics collected included age, ECOG performance status, Gleason score, extent of metastases, pretreatment PSA and albumin, radiation dose and fractionation, adjuvant systemic therapy and castrate resistance. Baseline PSA levels were measured before radiotherapy and at regular intervals after radiotherapy. Undetectable PSA was defined as <0.2 ng/ml.Results:
Patients in the study population had a Gleason score range of 6 to 10, with 76% classified as Gleason 8 to 10 and 23% having castrate-resistant disease. Additional baseline characteristics include median age 73 (IQR 66-80), 74% ECOG performance status 0 to 1, 63% metastases to bone only, 26% metastases to distant nodes only, 11% metastases to both bone and distant nodes, median PSA 24.0 ng/ml (IQR 4.7-82.7), and median albumin 4.0 g/dL (range 3.4-4.6). The prostate was treated in 71% of patients to a median dose of 72 Gy (IQR 60-79.2) in 32 fractions (IQR 20-43). Metastases were treated to a median dose of 40 Gy (IQR 30-60) in 10 fractions (IQR 3-38). The types of systemic therapy consisted of 91% androgen deprivation therapy, 66% androgen receptor pathway inhibitor, 9% docetaxel, 3% radium-223, 3% sipuleucel-T, and 3% none. Overall, 71% of patients cleared their PSA. Hormone-sensitive patients were significantly more likely to achieve PSA clearance than castrate-resistant patients (89% vs. 13%, OR = 4.0, 95% CI 1.6–6.4, p < 0.001). Among 25 patients with an undetectable PSA, only 2 have developed subsequent biochemical relapse to date.Conclusion:
Comprehensive involved site radiotherapy is effective at achieving undetectable PSA in patients with hormone-sensitive oligometastases. Longer-term follow-up is needed to determine if these results are durable.