medwireNews: Women with breast cancer have an increased long-term risk of hypertension and diabetes and this may be mediated by their cancer treatment type and BMI, suggests the Pathways Heart Study.
“These findings highlight patients with [breast cancer] as a vulnerable population at higher risk of developing cardiometabolic risk factors compared with the general population without a history of [breast cancer] and support targeted cardiovascular surveillance by specific patient and treatment characteristics to mitigate these risks,” say Marilyn Kwan (Kaiser Permanente Northern California, Oakland, USA) and team in the Journal of Clinical Oncology.
The case–control study included 14,942 patients with noninvasive breast cancer enrolled in the Kaiser Permanente Northern California cancer registry who were matched on birth year, race, and ethnicity, with 74,702 women in the database who did not have a breast cancer diagnosis. The average age of the study participants was 61.2 years and 65% were non-Hispanic White.
Over the mean 7-year follow-up, 11.98% of patients with breast cancer and 12.75% of those without breast cancer developed hypertension, with corresponding 2-year and 10-year cumulative incidence rates of 10.9% versus 8.9% and 23.9% versus 27.2%.
The rates of diabetes were 6.72% and 6.02% in women with and without breast cancer, respectively, with a higher cumulative incidence after 2 years among women with breast cancer, at 2.1%, compared to those without cancer at 1.7%. This higher incidence of diabetes persisted after 10 years among women with breast cancer relative to those without (9.3 vs 8.8%).
Multivariable analysis adjusted for factors including BMI, menopause, and smoking status revealed that women with breast cancer had a significantly higher risk for diabetes than those without breast cancer, with a subdistribution hazard ratio (sHR) of 1.16, but they did not have a significantly elevated risk for hypertension in this model.
The researchers investigated treatment-related risk factors for diabetes and hypertension and found that women given left-sided radiation therapy had the highest risk for developing diabetes with a significant adjusted sHR of 1.29, followed by chemotherapy and endocrine therapy, both with a significant adjusted sHR of 1.23, when compared with women who did not have breast cancer.
Women who had left-sided radiation and endocrine therapy, but not chemotherapy, also had a significantly higher risk for hypertension than those without breast cancer, with respective adjusted sHRs of 1.11 and 1.10.
The association between breast cancer and hypertension and diabetes was restricted to patients with a normal BMI (≤24.9 kg/m2); compared with controls, the corresponding sHRs were 1.18 and 1.35. No significant relationship was found for overweight or obese breast cancer patients.
Kwan et al say: “Future studies should examine the impact of targeted cardiometabolic risk factor management on cardiovascular events in subgroups of women with [breast cancer] on the basis of adjuvant therapy received and body size.”
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