PURPOSE: To investigate the utility of the interval to biochemical failure (IBF) after salvage radiation therapy (SRT) after radical prostatectomy (RP) for prostate cancer as a surrogate endpoint for distant metastasis (DM), prostate cancer-specific mortality (PCSM), and overall mortality (OM).
METHODS AND MATERIALS: 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.
RESULTS: 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 ≤18 months. There were no differences among any clinical or pathologic features between those with IBF ≤ and those with IBF >18 months. On log-rank analysis, IBF ≤ 18 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.
CONCLUSION: 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 ≤ 18 months may be useful in clinical practice or as an endpoint for clinical trials.
Written by:
Johnson S, Jackson W, Li D, Song Y, Foster C, Foster B, Zhou J, Vainshtein J, Feng F, Hamstra D. Are you the author?
Department of Radiation Oncology, The University of Michigan Medical Center, Ann Arbor, Michigan.
Reference: Int J Radiat Oncol Biol Phys. 2013 Apr 2. pii: S0360-3016(13)00184-3.
doi: 10.1016/j.ijrobp.2013.02.016
PubMed Abstract
PMID: 23561650
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