Factors associated with appropriate use of radiation therapy after mastectomy in women with Stage I-II breast cancer treated within the National Comprehensive Cancer Network (NCCN)

Abstract

6032 Background: Since 1996, the NCCN has published breast cancer practice guidelines. We examined rates and determinants of appropriate use of post-mastectomy radiation (RT), as defined by the guidelines, among women with Stage I-II breast cancer. Methods: Using detailed clinical characteristics, 1,620 consecutive patients at eight NCCN institutions who received mastectomy as definitive surgery between July 1997 and June 2002 were classified according to whether they fell onto guidelines that (1) recommended RT, (2) recommended against RT, or (3) made no definitive recommendation. We considered no RT in the first group as underuse, and RT in the third group as overuse. Multivariable logistic regression was applied to each group to investigate the association of clinical and sociodemographic factors with RT. Results: Of the entire cohort, 23.8% of women received RT; 83.6% (199/238), 5.6% (58/1029), and 38.6% (127/329) in the recommend, do not recommend, and consider groups, respectively. On multivariable analysis, the only factor associated with underuse was not receiving chemotherapy (p<0.0001). In addition to tumor characteristics, factors associated with overuse included younger age (p=0.048, <50 versus 50 years or older), NCCN institution (p=0.03), college education (p=0.001), and no immediate reconstruction (p=0.02). RT in the “consider” subgroup was strongly associated with NCCN institution (p<0.0001), mastectomy performed at a non-NCCN institution (p=0.004), younger age (p=0.04), as well as tumor characteristics. Conclusions: Overall, rates of concordance with definitive guidelines were high. The only factor associated with underuse was non-receipt of chemotherapy, suggesting these women may have chosen to forego aggressive treatment. Older age did not predict for underuse, but younger age was a significant predictor of overuse. When current evidence does not support a definitive recommendation for post-mastectomy RT, treatment decisions appear to be influenced by patient age, tumor factors and particularly by institution-specific patterns of care. No significant financial relationships to disclose.