Skeletal-related events (SRE) and bone-targeted agents for metastatic prostate cancer: Are we changing outcomes?

Abstract

e16074 Background: Bone-targeted agents (BTA) have been extensively studied in patients (pts) with prostate cancer (PC) and bone metastases (BM). Relatively little is known about the impact of BTAs on skeletal morbidity in the non-trial setting. We evaluated the impact BTAs on SRE and survival at a large Canadian cancer centre. Methods: Electronic heath records were reviewed for PC pts referred for further management from January 2008-June 2012. Demographic, clinical, and treatment data including: date of CRPC, occurrence of SRE, and BTA use were collected and analyzed. Results: A total of 141 pt charts were examined and were included in the analysis. Median age was 74 years (IQR 63-82), and 95% were stage IV at time of referral. Consequences of BMs included:101 pts had at least one SRE (72%), 58 (40%) pts had ≥1 SRE and 39% were hospitalised due to an SRE. Median overall survival from diagnosis of BM was 35.4 months (m) (IQR 16.1-65.9). Overall, 74 pts (52%) developed castration resistant PC (CRPC). In the CRPC group, the use of imaging to assess BM was highly variable, ranging from only once (12%) to every 1-2 m (4%), however the mode was every 3-5 m (43%). Sixty one percent (45/74) received a BTA, primarilyzoledronic acid (ZA). Despite having CRPC and BM, 39% never received a BTA, mainly because it was not offered (64%), or due to patient’s refusal (29%). Median time from diagnosis of CRPC to start of BTA was 1 month. Sixty-nine percent of pts had BTA discontinued, mainly due to progression of disease and pts deterioration. Osteonecrosis of the jaw occurred in 4% (2/45). In 39 pts (53%) the first SRE occurred prior to CRPC diagnosis, and 62 pts (84%) had at least 1 SRE after CRPC diagnosis. Forty seven percent (21/45) had a new SRE after starting BTA. Conclusions: BM have significant consequences for pts with PC irrespective of hormone sensitivity. Even for pts with CRPC the use of BTAs is highly variable. This reflects physician’s belief in the efficacy of BTAs, tailored by the expected benefits to each pt according to performance status and extent of disease. Interestingly in the CRPC group 53% have had an SRE prior to CRPC diagnosis. Strategies to optimise the care of pts with BM are clearly warranted.