Outcomes in real-world practice are different than cooperative trial for elderly patients with early breast cancer treated with adjuvant radiation therapy

Abstract

BackgroundThe Cancer and Leukemia Group B 9,343 demonstrated that postoperative radiation can be safely omitted in women ≥70 years who underwent breast-conserving therapy for clinical stage I (T1N0M0) estrogen receptor positive breast cancer treated with antihormonal therapy. Whether such results are observed in real-world population is unknown. In this hospital-based data, we report the survival outcomes of patients who received adjuvant radiation therapy versus those who did not. MethodsUsing the National Cancer Data Base, we evaluated a cohort of 47,358 women with newly diagnosed breast cancer between 2004 and 2011 who underwent a lumpectomy and antihormonal therapy with the following criteria: age ≥70 years, clinical stage I, estrogen receptor positive, and negative margins. Patients were stratified into 2 groups: (1) radiation therapy and (2) no radiation therapy. Propensity score matching was used to compensate for differences in demographic and clinical characteristics of the patients. Univariate and multivariable survival analysis were employed to determine factors associated with overall survival. ResultsThe 5-year overall survival after propensity score matching was 87.2% for radiation therapy and 79.4% for no radiation therapy (P < .0001). The median survival time was 113.7 months for radiation therapy and 105.2 months for no radiation therapy. After adjusting for sociodemographic and clinical factors, the risk of overall deaths was significantly higher for those not receiving radiation therapy (hazard ratio = 1.66; 95% confidence interval, 1.54–1.79). Other significant adjusted predictors (P < .05) of poor overall survival were, advanced age, comprehensive community cancer program, facility location, poorly differentiated tumor, and high comorbidity index. ConclusionPatients who received radiation therapy had better survival outcomes than those who did not, revealing discordance between results of randomized trials and real-world setting.