Radiation and survival in women over 70 with T1 N0 M0 ER-negative breast cancer from 1990 to 2007: A population-based analysis.

Abstract

1037 Background: The role of radiation therapy (RT) is controversial in older women (age ≥ 70) undergoing breast conserving therapy. While there is data that the omission of RT in women over 70 with estrogen receptor (ER) positive tumors who receive endocrine therapy is not associated with a survival difference, limited data exists for ER negative tumors in older women who undergo breast conservation. Methods: We used the Surveillance, Epidemiology, and End Results (SEER) database to identify women age ≥70 years diagnosed with Stage I invasive ductal breast cancer from 1990 – 2007 treated with lumpectomy. We extracted data on patient demographics, tumor characteristics, initial treatment, and survival. Breast cancer mortality (BCM) was defined as length of time from diagnosis to death by breast cancer, censored at last follow-up or death from other cause. We used the log-rank test to compare BCM, logistic regression to determine predictors of radiation use, and Cox proportional hazards model to determine the predictors of BCM. Results: We identified 26,652 older women (age ≥70) with Stage I invasive ductal breast cancer treated with lumpectomy. There were 2,882 (10.8 %) women with ER negative tumors. In this group, most patients (68.4%) received external beam RT, while 23.7 % received no RT. Among ER negative women, significant predictors of omission of RT were older age (Odds Ratio (OR) 1.37 CI 1.26−1.49 per 5 years), and failure to perform a pathologic lymph node evaluation (OR 2.82 CI 2.25−3.52). BCM rate at 5 years was reduced in patients with ER negative tumors treated with RT compared to no RT (5.6% vs 15.1%, p<0.001). On multivariate analysis, we found that omission of RT was associated with a 91% increased likelihood of BCM (Hazard Rate (HR) 1.91, p <0.001); other significant predictors of BCM were poorly differentiated grade (HR 1.46 p = 0.01), size > 1 cm (HR 1.70 p<0.001), and failure to perform a lymph node examination (HR 1.79 p<0.001). Race and income were not significant predictors of BCM among women with ER negative tumors. Conclusions: Adjuvant RT after lumpectomy significantly reduces BCM in women older than 70 with Stage I, ER negative breast cancers. RT is currently underutilized in these women.