e596 Background: It was ambiguous till now to evaluate the change of bone metastasis by various treatments. To quantify the change of bone metastases by enzalutamide, abiraterone, and docetaxel for the castration-resistant prostate cancer (CRPC) with bone metastases (bmCRPC), we employed Bone Scan Index (BSI) on bone scintigraphy. Methods: We retrospectively evaluated the change of PSA and bone metastases of CRPC patients who were treated with enzalutamide (Enz), abiraterone (Abi) and/or docetaxel (DOC) in our hospital. All patients underwent Tc-99m MDP bone scintigraphy. The degree of bone metastases was analyzed using BSI, which was calculated by BONENAVI (FUJIFILM RI Pharma, Japan; EXINIbone, EXINI Diagnostics, Sweden). 19 patients were treated with enzalutamide (8 cases: pre-docetaxel, 11 cases: post-docetaxel). The median PSA of patients treated with Enz was 12.64 ng/ml (1.63-199 ng/ml). And 11 patients were treated with abiraterone (5 cases: pre-docetaxel, 6 cases: post-docetaxel). The median PSA of patients treated with Abi was 26.37 ng/ml (2.29-199 ng/ml). Results: We observed decline of PSA in 18/30 cases (9 cases: pre-DOC, 9 cases: post-DOC). Decline of PSA to 50% or more was observed in 14 cases. In contrast, decline of BSI was observed in 53.3% (16/30) cases and decline of PSA to 25% or more was observed in only 6 cases. BSI decreased in 84.6% (11/13) of pre-DOC setting and in 29.4% (5/17) of post-DOC setting indicating that change of BSI was poor in post-DOC setting. However, DOC had already decreased BSI in 91.7% (11/12) before Abi or Enz treatment. Moreover, the average rate of BSI decline in the patients that BSI decreased by DOC was better than the patients that BSI decreased by Abi/Enz (-48.46% vs -28.56%). Finally, although the rate of BSI change by Enz was weakly correlated with the rate of PSA decline (y = 0.3906x + 25.35, R2 = 0.3423), BSI continued to increase in four cases in spite of PSA decline. Conclusions: BSI using BONENAVI on bone scintigraphy was helpful for evaluating the effectiveness of treatment and following-up of bmCRPC.
Bone scan index can be a useful biomarker of survival outcomes in patients with metastatic castration‐resistant prostate cancer treated with radium‐223
