Stereotactic Body Radiation Therapy for Oligoprogressive Disease in Androgen-Suppressed Prostate Cancer: Primary Endpoint Analysis of the TRAP Trial

Abstract

Purpose: Optimal management of oligoprogressive prostate cancer while on androgen receptor pathway inhibitors (ARPIs) is not known. The TRAP trial tests the role of stereotactic body radiation therapy (SBRT) in this setting. The objective of this phase 2 prospective, nonrandomized, single-arm trial was to determine if local control of oligoprogressive disease with SBRT can delay further progression by >4 months, postponing time to next therapy.

Methods and materials: Men with castration-resistant prostate cancer with ≤2 oligoprogressive sites developing on treatment with an ARPI, after initial response to therapy, were recruited. All patients were treated to a dose of 30 Gy in 5 fractions (alternate days) or 36 Gy in 6 fractions weekly (prostate only).

Results: Eighty-six men were recruited between October 2018 and February 2023. SBRT was delivered to 81 men. Mean age was 74 years. Most patients (67%) had 1 oligoprogressive disease lesion. Sites irradiated were bone (59%), lung (1%), lymph node (32%), and prostate (7%). Median follow-up was 22.9 months at the time of analysis. Fifty-five (68%) patients had progressed, 33 (41%) of patients progressed within 6 months of radiation therapy. Median progression-free survival (PFS) was 6.4 months (95% CI, 5.9-11.4). An estimated 39% (95% CI, 29-49) of patients have a prolonged PFS of > 12 months. Thirty-three (41%) of patients had started new treatment or died. Median time to either next treatment or death was 27.0 months (95% CI, 14.9-29.6). Median overall survival was 27.2 months (95% CI, 24.7-36.6). Four deaths occurred within 6 months of SBRT; none were related to radiation therapy treatment.

Conclusions: The TRAP trial has demonstrated a median PFS of 6.4 months after SBRT for oligoprogression of prostate cancer, meeting the primary endpoint. Further analysis of biomarker panel including circulating DNA and whole-body magnetic resonance imaging will promote better patient selection.