Original Research

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

Fed Pract. 2020 December;37(12):570-575 | 10.12788/fp.0062
Author(s):
Andrew Liman, MD
Rashmikant Shah, MD
Vida Passero, MD
Jocelyn Tan, MD
Hema Rai, MD
Laurie Harrold, MD
Joyce Tokarsky, CNS
Agnes Liman, MD
Vidhi Gupta, MD
Kristina Gerszten, MD
Author and Disclosure Information

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+).

M ethods: 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 2014 to 2018. 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 P 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 ( P = .005) for AO- veterans (the mean Gleason score 8.2 and 8.0, respectively [ P = .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) ( P = .93). The mean time to PSA progression for AO+ was 5.4 months and AO- was 6.8 months ( P = .28). Mean time to bone progression for AO+ was 7.6 months and AO- was 10.1 months ( P = .16). Mean time to ALP progression for AO+ and AO- was 6.3 months and 8.7 months, respectively ( P = .05). Twenty veterans (58%) had died. Median survival for Ra-223 first was 32 months and for Ra-223 later was 15 months ( P = .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 ( P = .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.
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References

Patients with metastatic castrate resistant prostate carcinoma (CRPC) have several treatment options, including radium-223 dichloride (Ra-223) radionuclide therapy, abiraterone, enzalutamide, and cabazitaxel. Ra-223 therapy has been reported to increase median survival in patients with bone metastatic prostate carcinoma.1,2 However, ERA 223 trial data showed an increase of bone fractures with combination of Ra-223 and abiraterone.3

Agent Orange (AO) exposure has been studied as a potential risk factor for development of prostate carcinoma. AO was a commercially manufactured defoliate that was sprayed extensively during the Vietnam War. Due to a side product of chemical manufacturing, AO was contaminated with the toxin 2,3,7,8-tetrachlorodibenzo-p-dioxin, a putative carcinogen. These dioxins can enter the food chain through soil contamination. There is enough evidence to link AO to hematologic malignancies and several solid tumors, including prostate carcinoma.4 Although no real estimates exist for what percentage of Vietnam veterans experienced AO exposure, Surveillance, Epidemiology, and End Results data showed that about 3 million veterans served in Southeast Asia where AO was used extensively in the combat theater. AO has been reported to be positively associated with a 52% increase in risk of prostate carcinoma detection at initial prostate biopsy.5

There has been no reported study of treatment efficacy in veterans with AO-related prostate carcinoma. We present a retrospective study of Ra-223 and other therapies in metastatic CRPC. The purpose of this study was to compare response to therapy and survival in veterans exposed to agent orange (AO+) vs veterans who were not exposed to (AO-) in a single US Department of Veteran Affairs (VA) medical center.

Methods

This was a retrospective study of veterans with metastatic CRPC to bones who received Ra-223 radionuclide therapy with standard dose of 50 kBq per kg of body weight and other sequential therapies at VA Pittsburgh Healthcare System (VAPHS) from January 2014 to January 2019. The purpose of this study was to measure difference in treatment outcome between AO+ veterans and AO- veterans.

Eligibility Criteria

All veterans had a history that included bone metastasis CRPC. They could have 2 to 3 small lymphadenopathies but not visceral metastasis. They received a minimum of 3 cycles and a maximum of 6 cycles of Ra-223 therapy, which was given in 4-week intervals. Pretreatment criteria was hemoglobin > 10 g/dL, platelet > 100 × 109/L, and absolute neutrophil counts > 1.5 × 109/L. Other therapies, such as abiraterone, enzalutamide, docetaxel, and cabazitaxel, were administered either after Ra-223 (Ra first) or before Ra-223 therapy (Ra later). Veterans also received androgen deprivation therapy (ADT) with luteinizing hormone releasing hormone (LHRH) agonist (leuprolide acetate) to maintain castrate level of testosterone and bisphosphonates for bone metastasis. Eligible veterans were divided into 2 groups: AO+ and AO-. AO+ veterans are those that were proven to be physically active during the Vietnam War and have been determined by the US government to receive service-connected compensation from the VA. AO- veterans were those who were not exposed to AO.

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