Vet Prostate Cancer Survivors Face Hidden Breast Cancer Risk

TOPLINE:

Among 1.3 million male veterans treated for prostate cancer, 11,327 (0.86%) developed breast cancer an average of 5.4 years after initial diagnosis. Younger age at prostate cancer diagnosis, metastatic disease, androgen deprivation therapy (ADT), radiation treatment, and prolonged use of certain cardiovascular disease (CVD) medications were associated with increased risk for breast cancer.

METHODOLOGY:

• Researchers used a retrospective cohort design in Veterans Health Administration (VHA) care, pulling data from the Veterans Affairs (VA) Prostate Cancer Data Core at the VA Corporate Data Warehouse.
• Participants included 1,314,492 male veterans with prostate cancer treated at VHA facilities from January 1, 2000, to March 12, 2024.
• Exposure definitions included prostate cancer treatments (ADT, anti-androgen treatment, radiation-brachytherapy, and platinum chemotherapy) and CVD medications (furosemide, spironolactone, digoxin) captured via inpatient/outpatient/fee-based pharmacy and Current Procedural Terminology codes.
• Analysis measured time from prostate cancer diagnosis to breast cancer diagnosis, death, or March 12, 2024, applying Cox proportional hazards and Fine-Gray competing risk methods, with a sensitivity analysis adding body mass index (BMI) after excluding 71,718 missing values.

TAKEAWAY:

• Metastatic prostate cancer at diagnosis more than doubled the risk for breast cancer compared to nonmetastatic disease (hazard ratio [HR], 2.03; 95% CI, 1.90-2.17; P < .0001; subdistribution hazard ratio [SHR], 1.68; 95% CI, 1.57-1.81; P < .0001).
• Younger age at prostate cancer diagnosis was associated with increased risk for breast cancer (HR, 0.97; 95% CI, 0.97-0.98; P < .0001; SHR, 0.957; 95% CI, 0.955-0.959; P < .0001), indicating that for each additional year of age at diagnosis, the risk decreased.
• Continuation of CVD medications after prostate cancer diagnosis was associated with increased risk for breast cancer: furosemide (HR, 1.51; 95% CI, 1.39-1.63; P < .0001; SHR, 1.21; 95% CI, 1.12-1.31; P < .0001), spironolactone (HR, 1.36; 95% CI, 1.15-1.61; P = .0004; SHR, 1.23; 95% CI, 1.04-1.47; P = .0174), and digoxin (HR, 1.49; 95% CI, 1.29-1.72; P < .0001; SHR, 1.26; 95% CI, 1.10-1.46; P = .0015).
• Radiation therapy and ADT were associated with increased risk for breast cancer (radiation: HR, 1.06; 95% CI, 1.02-1.11; P = .0088; SHR, 1.10; 95% CI, 1.05-1.15; P < .0001; ADT: HR, 1.24; 95% CI, 1.17-1.32; P < .0001; SHR, 1.28; 95% CI, 1.20-1.37; P < .0001), while abiraterone was associated with decreased risk (HR, 0.36; 95% CI, 0.31-0.42; P < .0001; SHR, 0.39; 95% CI, 0.34-0.45; P < .0001).

IN PRACTICE:

"While there is a lack of data, male veterans with previous prostate cancer are at an elevated risk of breast cancer (0.87%), than their civilian counterparts (0.14%),” the authors wrote. “To address the current gap in knowledge and data, this study leveraged an existing large cohort of male veterans with prostate cancer and examined factors associated with increased risk of male breast cancer."

SOURCE:

The study was led by Erum Z. Whyne, VA North Texas Health Care System in Dallas, and Haekyung Jeon-Slaughter, University of Texas Southwestern Medical Center in Dallas. It was published online in The Prostate.

LIMITATIONS:

Though the study findings are based on large, representative data from male veterans with previously diagnosed prostate cancer, the results might not be generalizable to the overall male breast cancer population. As a retrospective cohort study, results may be biased and causality is difficult to establish. The study did not examine other known risk factors for male breast cancer incidence, such as family history, BRCA2 mutations, and military environmental exposure due to lack of data. BMI had missingness of 5.46% (n = 71,718) and was not included as a covariate in the final model, though sensitivity analysis showed it was not significantly associated with increased risk for male breast cancer.

DISCLOSURES:

The research was supported using resources and facilities of the VA Informatics and Computing Infrastructure (VINCI), VA HSR RES 13-457. The VA North Texas Health Care System Institutional Review Board approved the study and waived informed consent. No conflicts of interest were disclosed by the authors.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.