Abstract
Background Almost 75% of breast cancer patients worldwide are treated with adjuvant therapy, primarily radiotherapy (RT). However, little is known about the long-term effects on cardiovascular health, particularly in older women.
Aims We studied nearly 800 women aged 65 years or older with early-stage breast cancer who received care through integrated health care plans to determine if cardiovascular disease (CVD) is associated with radiotherapy.
Methods Design & Data Elements: The retrospective cohort study, Breast Cancer Treatment in Older Women (BOW), included 806 women aged 65+ years diagnosed with stage I–II breast cancer between 1990 & 1994. These women were treated with surgery (breast conserving surgery [BCS] or mastectomy) and followed through 12/31/2004. Exclusions: Participants with CVD disease at baseline; those who had chemotherapy; or underwent BCS only without radiation treatment (i.e., less than standard care). Data elements: Demographic, treatment, tumor and comorbidity data from medical records, automated membership databases & SEER-affiliated cancer registries. CVD outcomes: acute myocardial infarction, angina pectoris, pericarditis, valvular dysfunction, cardiomyopathy, dysrhthymia, congestive heart failure and stroke. Exposure: Completed radiation treatment (RT) Statistical analysis: Adjusted hazard ratios (HR) and 95% confidence intervals were estimated using Cox models with time dependent tamoxifen & radiotherapy use status. Covariates included age, year of diagnosis, race/ ethnicity, stage, ER/PR status, laterality, comorbidities & health plan.
Results When comparing women who received RT with those who did not (full cohort, n=806), radiotherapy was not associated with greater risk of CVD after adjusting for multiple covariates including laterality (Table 2). However, within the subset exposed to RT (n=340), women treated for cancer of the left breast had a significant increase in CVD risk (HR=1.54, 1.07–2.23) compared with women treated with RT for the right breast.
Conclusions Preliminary results demonstrate that RT to the left breast may be associated with greater CVD risk. Our next study, “Long-Term Survivorship in Older Women with Early Stage Breast Cancer”(BOWII), will follow these women for an additional 5 years. This study will collect a wider set of risk factors for CVD to further evaluate these findings (2RO1CA093772-05A2 R. Silliman).
