Impact of CALGB 9343 Trial and Sociodemographic Variation on Patterns of Adjuvant Radiation Therapy Practice for Elderly Women (≥70 Years) with Stage I, Estrogen Receptor-positive Breast Cancer: Analysis of the National Cancer Data Base.

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.