When it comes to cardiovascular disease (CVD) risk after a breast cancer diagnosis, it’s not so much a matter of the amount of body fat carried but rather where it is located, results of a retrospective cohort study of nearly 3,000 survivors suggest.
“It is well known that higher body mass index (BMI) is associated with CVD mortality in the general population. However, BMI is not always an accurate proxy for individual-level adiposity and does not describe adipose tissue distribution,” note lead investigator Elizabeth M. Cespedes Feliciano, ScD, of Kaiser Permanente Northern California, Oakland, Calif., and coinvestigators.
The investigators studied 2,943 survivors of nonmetastatic breast cancer having a mean age of 56 years who were initially CVD free, using clinically acquired CT scans obtained near diagnosis to measure adiposity in three compartments: visceral, subcutaneous, and intramuscular.
The cohort experienced 328 CVD events (nonfatal stroke, myocardial infarction, heart failure, or CVD death) during a median follow-up of 6 years, the investigators reported in Journal of Clinical Oncology. The 10-year cumulative incidence was 15%.
In analyses that were adjusted for potential confounders and took into account competing risks, survivors’ CVD risk increased significantly with each standard deviation (SD) increase in visceral adiposity (hazard ratio, 1.15; 95% confidence interval, 1.03-1.29) and each SD increase in intramuscular adiposity (HR, 1.21; 95% CI, 1.06-1.37). The association for subcutaneous adiposity was not significant.
Findings were similar across all BMI categories. Of particular note, among survivors having a normal BMI, risk of CVD events increased by 70% with each SD greater visceral adiposity (HR, 1.70; 95% CI, 1.10-2.62).
Risk also rose with BMI exceeding the normal range, but the association became significant only in survivors with a BMI placing them in obesity class II (35 kg/m2 or greater) (HR, 1.70; 95% CI, 1.20-2.42).
“Although it has been assumed that excess adiposity increases the risk of CVD after breast cancer, this first-of-its-kind study demonstrates that adipose tissue distribution best identifies patients with breast cancer with higher CVD risk after diagnosis, including those with normal BMI,” Dr. Cespedes Feliciano and coinvestigators note.
“Software is now available that automatically measures body composition from clinically acquired CT scans, facilitating clinical integration,” they note. “Measures of adipose tissue distribution from CT or anthropometry (e.g., waist circumference) may help identify individuals with high CVD risk and tailor prevention efforts to patients’ body composition.”
Dr. Cespedes Feliciano disclosed no relevant conflicts of interest. The study did not receive any specific funding.
SOURCE: Cespedes Feliciano EM et al. J Clin Oncol. 2019 Aug 1. doi: 10.1200/JCO.19.00286.