The Effect of Radium-223 Therapy in Agent Orange-Related Prostate Carcinoma.

BACKGROUND

Radium-223 (Ra-223) radioisotope has been reported to increase median survival in bone metastatic prostate carcinoma. The addition of Ra-223 to abiraterone was associated with an increased risk of bone fractures. There has been no comprehensive data for using Ra-223 in veterans who were exposed to Agent Orange (AO+).

METHODS

We present a retrospective study of veterans with bone metastatic castration-resistant prostate cancer (CRPC) who received standard doses of Ra-223 and other sequential therapies at US Department of Veterans Affairs Pittsburgh Healthcare System in Pennsylvania from January 2014 to January 2019. Veterans were divided into 2 groups: those who were exposed to Agent Orange (AO+) and those who had no exposure (AO-). Time to study was calculated from the initiation of Ra-223. 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 values. Median survival was calculated by Kaplan Meier R log-rank test.

RESULTS

There were 34 veterans with bone metastatic CRPC: 17 veterans (50%) were AO+ and 17 veterans (50%) were AO-. The mean age of diagnosis of AO+ veterans was 62 years and 69 years ( = .005) for AO- veterans (the mean Gleason score 8.2 and 8.0, respectively [ = .71]). The median number of Ra-223 cycles was 6 (60%). Ten veterans received Ra-223 as first line (29%) and 24 veterans received Ra-223 later (71%). There were 12 SREs with median survival of 15 months. There was no difference in mean time to SRE between AO+ (8 veterans, 10.6 months) and AO- (4 veterans, 10.3 months) ( = .93). The mean time to PSA progression for AO+ was 5.4 months and AO- was 6.8 months ( = .28). Mean time to bone progression for AO+ was 7.6 months and AO- was 10.1 months ( = .16). Mean time to ALP progression for AO+ and AO- was 6.3 months and 8.7 months, respectively ( = .05). Twenty veterans (58%) had died. Median survival for Ra-223 first was 32 months and for Ra-223 later was 15 months ( = .14; hazard ratio [HR] 0.48; 95% CI, 0.17-1.3). Median survival for AO+ and AO- veterans was 12 months and 18 months, respectively ( = .15; HR, 2.0; 95% CI, 0.77-5.0).

CONCLUSIONS

There was no statistical difference between AO+ and AO- veterans in terms of time to SRE, PSA, bone and ALP progression, even though there was a trend of shorter duration in AO+ veterans. There was no median survival difference between Ra-223 first vs Ra-223 later as well as between AO+ and AO- but there is a trend of worse survival in AO+ veterans.