Metabolic syndrome is associated with increased mortality in patients with breast or prostate cancer

We investigated the association of metabolic syndrome (MetS) with mortality in patients with breast and prostate cancer. Breast and prostate cancer cohorts were created retrospectively using the SEER-Medicare database. Patients with first primary breast or prostate cancer diagnosed in 2008-2019 were identified using ICD-O-3 site and histology codes. Among those, patients with MetS were identified using ICD-9/10-CM codes, CPT/HCPCS codes, and prescription drug use from Medicare claims files. We defined continuous enrollment from 12 months before through 12 months after diagnosis, exposure during the first 12 months after diagnosis, and survival follow-up starting 12 months after diagnosis. We used multivariable Cox regression to assess the association of MetS with overall, cancer-specific, cardiovascular-specific, and liver-failure-specific mortality, adjusted for age at diagnosis, race/ethnicity, marital status, diagnosis year, cancer stage, SEER region, and metropolitan area. We identified 104,599 breast cancer patients, 28% of whom had MetS, and 96,005 prostate cancer patients, 31% of whom had MetS. In both cohorts, MetS was associated with increased overall mortality (breast cancer: hazard ratio [HR] 2.03; 95% CI 1.98-2.08; prostate cancer: HR 2.21; 95% CI 2.15-2.27), increased cancer-specific mortality (breast cancer: HR 1.30 (95% CI 1.21-1.39; prostate cancer (HR 1.32 (95% CI 1.22-1.42), increased cardiovascular-specific mortality (breast cancer: HR 2.27; 95% CI 2.11-2.45; prostate cancer: HR 2.46; 95% CI 2.27-2.66), and increased liver-failure-specific mortality (breast cancer: HR 2.55; 95% CI 1.48-4.42; prostate cancer: HR 3.26; 95% CI 1.83-5.82). Therapeutic and lifestyle interventions are needed to reduce mortality risk in breast and prostate cancer patients with MetS.