Q. D. Chu1, P. Peddi1, M. Zhou2, K. Medeiros2, X. Wu2 1Louisiana State University Health Sciences Center,Surgery,Shreveport, LA, USA 2Louisiana State University Health Sciences Center,Biostatistics,New Orleans, LA, USA
Introduction: Clinical trials demonstrated the efficacy of omitting radiation therapy (RT) for women ≥ 70 years old, hormone receptor positive (HR+) T1 breast cancer who underwent breast-conserving therapy cancer treated with anti-hormonal therapy. Whether such results also apply to real-world population is unknown. We report the survival outcomes of patients who received adjuvant RT versus those who did not using a large national clinical oncology database.
Methods: Using the National Cancer Data Base, representing about 70% of newly diagnosed cancer cases nationwide, we evaluated a cohort of 66,763 women diagnosed with breast cancer in 2004 -2012 and meeting the following criteria: age ≥ 70 years, pathologic stage I, HR+, negative margins, and receipt of anti-hormonal therapy. Patients were stratified into two groups: (1) RT and (2) no RT. Propensity score matching was used to compensate for differences in baseline characteristics. Univariate and multivariable survival analysis with Cox proportional hazards models were employed to determine the impact of radiation therapy on the overall survival (OS).
Results:After matching, 23,276 cases were analyzed. The 5-year OS was 85.9% for RT group and 78.3% for no RT group (HR=1.59; P<0.0001). The median survival time was 114.07 months for RT and 103.56 months for no RT. Significant adjusted predictors (P<0.01) of poor OS were lack of radiation, advanced age, facility type, facility location, and high comorbidity score.
Conclusion:Patients who received RT had better survival outcomes than those who did not, revealing discordance between results of randomized trials and real-world setting.
