Deep and durable prostate-specific antigen response following comprehensive involved site radiotherapy for prostate cancer oligometastases.

BACKGROUND AND

OBJECTIVE

Achieving undetectable prostate-specific antigen (PSA) has been correlated with improved outcomes for patients with metastatic prostate cancer. Comprehensive involved site radiotherapy (ISRT) consisting of local therapy to the prostate and radiation to all visible metastases has emerged as a method of treatment intensification for prostate cancer oligometastases. The objective of this study was to evaluate the frequency and predictors of undetectable PSA in patients who received radiotherapy for oligometastases.

METHODS

Thirty-five consecutive men with oligometastatic prostate cancer were treated with comprehensive ISRT with a median follow-up of 33.3 months. Undetectable PSA was defined as <0.2 ng/ml. The primary outcome of interest was the prognostic significance of undetectable PSA following combined radiotherapy and systemic treatment. Bivariate comparisons were conducted using Fisher's exact and Mann-Whitney U tests, and multivariate comparisons were made with Cox and logistic regressions.

RESULTS AND LIMITATIONS: Baseline characteristics include median age 73, median PSA 24.0 ng/ml, 74% Gleason 8 to 10, 77% hormone sensitive, 74% bone metastases, 37% distant lymph node metastases, 60% PSMA PET staged. Overall, 74% of patients achieved a PSA nadir of <0.2 ng/ml. Hormone-sensitive patients were significantly more likely to achieve PSA clearance than castrate-resistant patients (93% vs. 12.5%). Patients achieving a PSA nadir of <0.2 ng/ml had a 3-year disease-free survival of 86% vs. 22% for patients with a higher PSA nadir (P < 0.001).

CONCLUSIONS

Comprehensive ISRT is effective at achieving undetectable PSA in patients with hormone-sensitive oligometastatic prostate cancer. Longer-term follow-up is needed to determine if these results are durable.