Outcomes and prognostic factors in intermediate-risk prostate cancer: multi-institutional analysis of the Spanish...

To retrospectively assess outcomes and to identify prognostic factors in patients diagnosed with intermediate-risk (IR) prostate cancer (PCa) treated with primary external beam radiotherapy (EBRT).

Data were obtained from the multi-institutional Spanish RECAP database, a population-based prostate cancer registry in Spain. All IR patients (NCCN criteria) who underwent primary EBRT were included. The following variables were assessed: age; prostate-specific antigen (PSA); Gleason score; clinical T stage; percentage of positive biopsy cores (PPBC); androgen deprivation therapy (ADT); and radiotherapy dose. The patients were stratified into one of three risk subcategories: (1) favourable IR (FIR; GS 6, ≤ T2b or GS 3 + 4, ≤ T1c), (2) marginal IR (MIR; GS 3 + 4, T2a-b), and (3) unfavourable IR (UIR; GS 4 + 3 or T2c). Biochemical relapse-free survival (BRFS), disease-free survival (DFS), cancer-specific survival (CSS), and overall survival (OS) were assessed.

A total of 1754 patients from the RECAP database were included and stratified by risk group: FIR, n = 781 (44.5%); MIR, n = 252 (14.4%); and UIR, n = 721 (41.1%). Mean age was 71 years (range 47-86). Mean PSA was 10.4 ng/ml (range 6-20). The median radiotherapy dose was 74 Gy, with mean doses of 72.5 Gy (FIR), 73.4 Gy (MIR), and 72.8 Gy (UIR). Most patients (88%) received ADT for a median of 7.1 months. By risk group (FIR, MIR, UIR), ADT rates were, respectively, 88.9, 86.5, and 86.9%. Only patients with ≥ 24 months of follow-up post-EBRT were included in the survival analysis (n = 1294). At a median follow-up of 52 months (range 24-173), respective 5- and 10-year outcomes were: OS 93.6% and 79%; BRFS 88.9% and 71.4%; DFS 96.1% and 89%; CSS 98.9% and 94.6%. Complication rates (≥ grade 3) were: acute genitourinary (GU) 2%; late GU 1%; acute gastrointestinal (GI) 2%; late GI 1%. There was no significant association between risk group and BRFS or OS. However, patients with favourable-risk disease had significantly better 5- and 10-year DFS than patients with UIR: 98.7% vs. 92.4% and 92% vs. 85.8% (p = 0.0005). CSS was significantly higher (p = 0.0057) in the FIR group at 5 (99.7% vs. 97.3%) and 10 years (96.1% vs. 93.4%). On the multivariate analyses, the following were significant predictors of survival: ADT (BRFS and DFS); dose ≥ 74 Gy (BRFS); age (OS).

This is the first nationwide study in Spain to report long-term outcomes of patients with intermediate-risk PCa treated with EBRT. Survival outcomes were good, with a low incidence of both acute and late toxicity. Patients with unfavourable risk characteristics had significantly lower 5- and 10-year disease-free survival rates. ADT and radiotherapy dose ≥ 74 Gy were both significant predictors of treatment outcomes.