A retrospective analysis of 575 patients treated with SRT after RP from a single institution. Of those, 250 patients experienced biochemical failure (BF), with the IBF defined as the time from commencement of SRT to BF. The IBF was evaluated by Kaplan-Meier and Cox proportional hazards models for its association with DM, PCSM, and OM.
The median follow-up time was 85 (interquartile range [IQR] 49.8-121.1) months, with a median IBF of 16.8 (IQR, 8.5-37.1) months. With a cutoff time of 18 months, as previously used, 129 (52 % ) of patients had IBF ¡Ü18 months. There were no differences among any clinical or pathologic features between those with IBF ¡Ü and those with IBF >18 months. On log-rank analysis, IBF ¡Ü18 months was prognostic for increased DM (P<.0001, HR 4.9, 95 % CI 3.2-7.4), PCSM (P<.0001, HR 4.1, 95 % CI 2.4-7.1), and OM (P<.0001, HR 2.7, 95 % CI 1.7-4.1). Cox proportional hazards models with adjustment for other clinical variables demonstrated that IBF?was independently prognostic for DM (P<.001, HR 4.9), PCSM (P<.0001, HR 4.0), and OM (P<.0001, HR 2.7). IBF showed minimal change in performance regardless of androgen deprivation therapy (ADT) use.
After SRT, a short IBF can be used for early identification of patients who are most likely to experience progression to DM, PCSM, and OM. IBF ¡Ü18 months may be useful in clinical practice or as an endpoint for clinical trials.