In the case-control Pathways Heart Study reported in the Journal of Clinical Oncology, Kwan et al found that breast cancer survivors had an elevated risk for incident diabetes overall and according to treatment as well as an elevated risk of incident hypertension according to treatment vs controls with no history of breast cancer.
Study Details
In the study, 14,942 patients with breast cancer diagnosed between 2005 and 2013 at Kaiser Permanente Northern California were matched 1:5 for birth year, race, and ethnicity with 74,702 controls who had no history of breast cancer. Cumulative incidence rates of new-onset hypertension, diabetes, and dyslipidemia were estimated with competing risk of overall death. In multivariate analysis, subdistribution hazard ratios (sHR) were adjusted for cardiovascular disease–related risk factors and stratified by treatment and body mass index (BMI).
Key Findings
Cases had a mean age of 61.2 years; 65% were White, 14% were Asian, 12% were Hispanic, and 7% were Black. Mean follow-up was 7.0 years (range = < 1.0–13.4 years).
Breast cancer survivors at Kaiser Permanente Northern California experienced elevated risks of diabetes and hypertension compared with women without breast cancer depending on treatments received and BMI. Future studies should examine strategies for cardiometabolic risk factor prevention in breast cancer survivors.— Kwan et al
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Cases had a greater cumulative incidence of hypertension (10.9% vs 8.9%) and diabetes (2.1% vs 1.7%) after 2 years, with a greater incidence of diabetes persisting after 10 years (9.3% vs 8.8%). At 10 years, the incidence of hypertension was greater in controls (23.9% v 27.2%). The cumulative incidence of dyslipidemia was consistently lower among cases, particularly at 10 years (23.7% vs 27.0%).
In multivariate models for the entire follow-up duration, cases had a significantly increased risk of diabetes (sHR = 1.16, 95% confidence interval [CI] = 1.07–1.26) but not hypertension (sHR = 1.02, 95% CI = 0.97–1.08) and a lower risk of dyslipidemia (sHR = 0.90, 95% CI = 0.86–0.95) vs controls.
In analysis by treatment, an increased risk of diabetes was observed among cases receiving chemotherapy (sHR = 1.23, 95% CI = 1.11–1.38), left-sided radiation (sHR = 1.29, 95% CI = 1.13–1.48), or endocrine therapy (sHR = 1.23, 95% CI = 1.12–1.34) vs controls. An increased risk of hypertension was observed among cases receiving left-sided radiation (sHR = 1.11, 95% CI = 1.02–1.21) or endocrine therapy (sHR = 1.10, 95% CI = 1.03–1.16).
Normal-weight (BMI < 24.9 kg/m2) cases—but not overweight or obese cases—had an increased risk of hypertension (sHR = 1.18, 95% CI = 1.07–1.30) and diabetes (sHR = 1.35, 95% CI = 1.09–1.67) vs controls, with an increased risk for both also observed in normal-weight treatment subgroups.
The investigators concluded, “Breast cancer survivors at Kaiser Permanente Northern California experienced elevated risks of diabetes and hypertension compared with women without breast cancer depending on treatments received and BMI. Future studies should examine strategies for cardiometabolic risk factor prevention in breast cancer survivors.”
Marilyn L. Kwan, PhD, of the Division of Research, Kaiser Permanente Northern California, Oakland, is the corresponding author for the Journal of Clinical Oncology article.
Disclosure: The study was supported by grants from the National Cancer Institute. For full disclosures of the study authors, visit ascopubs.org.
