Statistics
Time to study was calculated from the initiation of Ra-223 therapy. Time to skeletal-related events (SRE), progression of prostate specific antigen (PSA), bone metastasis, and alkaline phosphatase (ALP) were calculated in months, using unpaired t test with 2-tailed P value. Median survival was calculated in months by Kaplan Meier R log-rank test Definition).
Results
Forty-eight veterans with bone metastasis CRPC received Ra-223 therapy. Of those, 34 veterans were eligible for this retrospective study: 17 AO+ veterans and 17 AO- veterans. Mean age of diagnosis was 62 years (AO+) and 69 years (AO-) (P = .005). Mean Gleason score was 8.2 (AO+) and 8.0 (AO-) (P = .705). Veterans received initial therapy at diagnosis of prostate carcinoma, including radical prostatectomy (6 AO+ and 3 AO-), localized radiation therapy (3 AO+ and 5 AO-), and ADT (8 AO+ and 9 AO-) (Table 1).
Mean PSA at the initiation of Ra-223 therapy for AO+ was 92.8 (range, 2-551) and for AO- was 102.3 (range, 4-639; P = .86). Mean Ra-223 dose per cycle for AO+ and AO- was 157 uCi and 113 uCi, respectively. All 34 veterans received ADT (leuprolide acetate), and 30 veterans (16 AO+ and 14 AO-) received bisphosphonates (zoledronic acid or denosumab). A total of 10 veterans (29%) received Ra-223 as a first-line therapy (4 AO+ and 6 AO-), and 24 veterans (71%) received Ra-223 after hormonal or chemotherapy (13 AO+ and 11 AO-).
There were 12 SRE (8 AO+ and 4 AO-). Mean time to SRE for AO+ was 10.6 months and AO- was 10.3 months (P = .93). Three veterans received concurrent Ra-223 and abiraterone (participated in ERA 223 trial). Two AO+ veterans experienced SRE at 7 months and 11 months, respectively. Mean time to PSA progression for AO+ was 5.4 months and for AO- was 6.8 months (P = .28). Mean time to bone progression for AO+ and for AO- were 7.6 months and 10.1 months, respectively (P = .16). Mean time to ALP progression for AO+ and AO- were 6.3 months and 8.7 months, respectively (P = .05). (Table 2). The treatment pattern of AO+ and AO- is depicted on a swimmer plot (Figures 1 and 2).
Twenty veterans (58%) had died: 13 AO+ and 7 AO- veterans. Median survival for Ra-223 first and Ra-223 later was was 32 months and 15 months, respectively (P = .14; hazard ratio [HR], 0.48). Overall median survival for AO+ veterans and AO- veterans were 12 months and 18 months, respectively (P = .15; HR, 2.0) (Figures 3 and 4).
Discussions
There has been no reported VA study of using Ra-223 and other therapies (hormonal and chemotherapy) in veterans exposed to AO. This is the first retrospective study to compare the response and survival between AO+ and AO- veterans. Even though this study featured a small sample, it is interesting to note the difference between those 2 populations. There was 1 prior study in veterans with prostate carcinoma using radiotherapy (brachytherapy) in early-stage disease. Everly and colleagues reported that AO+ veterans were less likely to remain biochemically controlled compared with AO- and nonveteran patients with prostate carcinoma.4