Background: The Cancer and Leukemia Group B (CALGB) 9343 trial demonstrated that adjuvant radiation therapy (RT) can be omitted in women 70 years or older, with small (≤2 cm), negative lymph nodes, estrogen receptor (ER)-positive breast cancer. We examined whether RT usage following the CALGB publication had decreased over time and evaluated sociodemographic and clinical factors associated with RT omission.
Materials and methods: From the National Cancer Data Base, we analyzed a cohort of 120,308 women aged 70 years or older with stage I, ER-positive breast cancer who underwent lumpectomy. Patients were classified into two groups based on the time of CALGB 9343 publication: (i) pre-CALGB (up to 2004), and (ii) post-CALGB (2005-2012). Clinicopathological and sociodemographic variables were compared between pre- and post-CALGB groups. Chi-square and multivariable logistic regression were employed, with the omission of adjuvant RT as the primary outcome in the regression analysis.
Results: Radiation therapy usage decreased by 4.1% after CALGB publication (on average 71.6% pre-CALGB vs. 67.5% post-CALGB; p<0.0001). Almost one-third of women aged ≥85 years received RT in the post-CALGB group. In a multivariable model, the variables significantly associated with increased odds for omission of RT in the post-CALGB group were: advanced age, African-American, increased great circle distance, therapy under academic research program, residents of East South-Central region, living in a rural population <2,500 not adjacent to a metropolitan area, low income level, Medicaid recipients, high comorbidity index, small tumor, well-differentiated histology, residual tumor, and lack of receipt of chemotherapy and anti-hormonal therapy.
Conclusion: During the study period, the CALGB trial publication had a minimal impact on the rate of adjuvant RT use among elderly women with small, ER-positive breast cancers. Significant variation in RT usage existed across sociodemographic strata.
Keywords: ER+; Elderly; adherence; breast cancer; hormone-positive breast cancer; radiation therapy; small breast cancer; stage I breast cancer.
Copyright© 2017, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.