Evaluation of bone metastasis and prognosis of prostate cancer with bone metastasis during standard hormonal therapy and chemotherapy: A report of PROSTAT-BSI multicenter registry in Japan.

Abstract

215 Background: Quantitative evaluation of the change of bone metastasis (bMet) has not been clearly defined during treatments in prostate cancer (PCa). As therapeutic effects of bMet have become quantified with scintigraphic bone scan index (BSI), we performed a nation-wide observational prospective study in patients who were treated by hormonal therapy (HTx) or chemotherapy (CTx). Methods: A total of 237 patients were recruited at 30 hospitals in Japan, and this report summarized baseline demographics and prognosis of 203 patients. All had bMet and underwent either standard HTx (group H) or docetaxel CTx (group C). Bone scans were performed with 99mTc-MDP. Patients were followed up for 3 years, and changes in biochemical and tumor markers during HTx and CTx were recorded in addition to skeletal-related events, recurrence, and death. Results: The basic characteristics of the patients (n=203) at the time of registration during December 2016 were as follows: mean age 71 ± 8 years; median BSI calculated on-site 3.0 ± 3.2% and median PSA was 265 ng/mL (22-2923 ng/mL) and 33 (3-537 ng/mL), for Group H and C (p=0.0014), respectively. BSI was comparable (H: 3.0 ± 3.4 vs C: 3.0 ± 2.8%, p=n.s.) between the two groups. A total of 54 patients (24%) died from PCa. BSI flare defined as increase at 3 months and decrease at 6 months was 13% and 31% (p<0.0069) for Groups H and C, respectively. When patients were classified into three groups with BSI <0.9 (low), 0.9-3.3 (intermediate), and >3.3% (high). Kaplan-Meier Survival analysis showed that mortality at 1100 days was 8%, 16%, and 35% for Group H (p=0.0097), and 50%, 55%, and 65% for Group C (p=ns) for the low, intermediate and high BSI group, respectively. In addition, patients who showed BSI decline >20% until 6 months showed better prognosis than those who did not (p<0.0001 and p= 0.038 and for Group H and C, respectively). Conclusions: The data of PROSTAT-BSI showed that BSI could be a good biomarker for prognosis in both Groups H and C, in particular for prognostic stratification of patients indicated for HTx. Six-month response of BSI by >20% indicated better prognosis in both groups. Clinical trial information: UMIN000007858.