Ansbaugh and colleagues reported that AO was associated with a 75% increase in the risk of Gleason ≥ 7 and a 110% increase in Gleason ≥ 8. AO+ veterans are at risk for the detection of high-grade prostate carcinoma. They also tend to have an average age of diagnosis that is 4 to 5 years younger than AO- veterans.6
Our study revealed that AO+ veterans were diagnosed at a younger age (mean 62 years) compared with that of AO- veterans (mean 69 years, P = .005). We also proved that AO veterans have a higher mean Gleason score (8.2) compared with that of AO- veterans (8.0). Veterans received therapy at the time of diagnosis of prostate carcinoma with either radical prostatectomy, radiation therapy, or ADT with leuprolide acetate. Mean PSA at the start of Ra-223 therapy for AO+ was 92.8 (range, 2-551); for AO- was 102.3 (range, 4-639), which is not statistically significant.
Ra-223, an α-emitting radiopharmaceutical, mimics calcium in forming complexes with the bone mineral hydroxyapatite, which specifically targets bone metastases. Ra-223 preferentially targets new bone growth surrounding bone metastases while emitting α particles within the tumor microenvironment. α particles have high linear energy transfer with enhanced ability to induce lethal double-stranded DNA breaks, thus eliciting greater cytotoxic effects on bone-metastatic tumor sites.7
In a phase 3, randomized, double-blind, placebo-controlled study by Parker and colleagues (ALSYMPCA study), 921 patients who had received, were not eligible to receive, or declined docetaxel, in a 2:1 ratio, were randomized to receive 6 injections of Ra-223 or matching placebo.2 Ra-223 significantly improved overall survival (OS) (median, 14.9 months vs 11.3 months) compared with that of placebo. Ra-223 also prolonged the time to the first symptomatic SRE (median, 15.6 months vs 9.8 months), the time to an increase in the total ALP level (median 7.4 months vs 3.8 months), and the time to an increase in the PSA level (median 3.6 months vs 3.4 months).2
In our study, the mean time to SRE for AO+ was 10.6 months and AO- was 10.3 months (P = .93). 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). There is a trend of shorter PSA progression, bone progression, and ALP progression in AO+ veterans, though these were not statistically significant due to small sample population. In our study the median survival in for AO- was 18 months and for AO+ was 12 months, which is comparable with median survival of 14.9 months from the ALSYMPCA study.
There were 12 veterans who developed SREs. All received radiation therapy due to bone progression or impending fracture. AO+ veterans developed more SREs (n = 8) when compared with AO- veterans (n = 4). There were more AO- veterans alive (n = 10) than there were AO+ veterans (n = 4). The plausible explanation of this may be due to the aggressive pattern of prostate carcinoma in AO+ veterans (younger age and higher Gleason score).
VAPHS participated in the ERA trial between 2014 and 2016. The trial enrolled 806 patients who were randomly assigned to receive first-line Ra-223 or placebo in addition to abiraterone acetate plus prednisone.3 The study was unblinded prematurely after more fractures and deaths were noted in the Ra-223 and abiraterone group than there were in the placebo and abiraterone group. Median symptomatic SRE was 22.3 months in the Ra-223 group and 26.0 months in the placebo group. Fractures (any grade) occurred in 29% in the Ra-223 group and 11% in the placebo group. It was suggested that Ra-223 could contribute to the risk of osteoporotic fractures in patients with bone metastatic prostate carcinoma. Median OS was 30.7 months in the Ra-223 group and 33.3 months in the placebo group.3
We enrolled 3 veterans in the ERA clinical trial. Two AO+ veterans had SREs at 7 months and 11 months. In our study, the median OS for Ra-223 first line was 32 months, which is comparable with median survival of 30.7 months from ERA-223 study. Median survival for Ra-223 later was only 15 months. We recommend veterans with at least 2 to 3-bone metastasis receive Ra-223 in the first-line setting rather than second- or third-line setting. In this retrospective study with Ra-223 and other therapies, we proved that AO+ veterans have a worse response and OS when compared with that of AO- veterans.
