Prognostic Risk Classification for Biochemical Relapse-Free Survival in Oligometastatic Recurrent Prostate Cancer Determined by Choline PET

Choline positron emission tomography/computed tomography (PET/CT) is a new imaging technique for the detection of oligometastatic (OM) prostate cancer. The aim of this study was to evaluate the outcomes after initial OM diagnoses; treatment, particularly metastasis-directed therapy (MDT); and determine risk groups. This multi-center, retrospective study included patients with hormone-sensitive biological relapse after local treatment with curative intent and with fewer than six choline PET/CT metastases. The primary endpoint was biochemical relapse-free survival (bRFS). Risk groups were based on prostate-specific antigen (PSA) ≥ 0.8 ng/mL and metastatic sites at OM cancer diagnosis. Between October 2012 and December 2016, 177 patients were included, with a median follow-up of 49.02 months. The median bRFS was 39.74 months. In multivariate analyses, bone metastases and PSA ≥ 0.8 ng/mL were associated with worse bRFS. Four risk groups (I to IV; hazard ratio [HR], 5.92; 95% confidence interval [CI], 1.32-26.61) were observed, with median bRFS not reached for group I (PSA < 0.8 ng/mL; node metastasis [M1a]), a 40.00-month bRFS for group II (PSA ≥ 0.8 ng/mL; M1a), 29.97-month bRFS for group III (bone metastasis [M1b], whatever the PSA level); and 22.70-month bRFS for group IV (PSA > 0.8 ng/mL and visceral metastasis [M1c]). MDT plus androgen deprivation therapy (ADT) improved bRFS over MDT alone (48.36 vs. 34.16 months; HR, 2.12; 95% CI, 1.38-3.26), particularly for group II (HR, 2.09; 95% CI, 1.09-4.00), and reached a limit of significance for group III (HR, ;3.79 95% CI, 0.88- 16.38). Prognostic group classifications were confirmed: PSA < 0.8 ng/mL and M1a showed a better outcome than patients with M1c and PSA ≥ 0.8 ng/mL. These results could facilitate patient selection for prospective clinical trials in OM prostate cancer. This retrospective, multi-center study evaluated oligometastatic prostate cancer with regard to choline positron emission tomography/computed tomography, outcome, and determine risk groups. The study included 177 patients with a median follow-up of 49.02 months. In multivariate analysis, bone metastases and prostate-specific antigen (PSA) ≥ 0.8 ng/mL were associated with worse biological relapse-free survival. Based on metastatic site and PSA, four risk groups were identified (I to IV; hazard ratio, 5.92; 95% confidence interval, 1.32-26.61). These results could facilitate patient selection for prospective clinical trials.