Factors Associated With Guideline-Concordant Use of Radiotherapy After Mastectomy in the National Comprehensive Cancer Network

We examined the rates and determinants of appropriate and inappropriate use of postmastectomy radiotherapy (PMRT), as defined by the National Comprehensive Cancer Network (NCCN) practice guidelines, among women with Stage I-II breast cancer (American Joint Committee on Cancer, 5th edition).Using clinical characteristics, 1,620 consecutive patients at eight NCCN institutions who had undergone mastectomy between July 1997 and June 2002 were classified into three cohorts according to whether the guidelines (1) recommended PMRT, (2) recommended against PMRT, or (3) made no definitive PMRT recommendation. We defined the absence of PMRT in the first cohort as underuse and receipt of PMRT in the second cohort as overuse. Multivariate logistic regression analysis was applied to investigate the association of clinical and sociodemographic factors with PMRT.Overall, 23.8% of patients received PMRT. This included 199 (83.6%) of 238 in the "recommend PMRT" cohort, 58 (5.6%) of 1,029 in the "recommend against PMRT" cohort, and 127 (38.6%) of 329 in the "consider PMRT" cohort. The only factor associated with underuse in the "recommend PMRT" cohort was nonreceipt of chemotherapy (odds ratio [OR], 0.08; p0.0001). In addition to tumor characteristics, the factors associated with overuse in the "recommend against PMRT" cohort included age50 years (OR, 2.28; p = 0.048), NCCN institution (OR, 1.04-8.29; p = 0.026), higher education (OR, 3.49; p = 0.001), and no reconstructive surgery (OR, 2.44; p = 0.019). The factors associated with PMRT in the "consider PMRT" cohort included NCCN institution (OR, 1.1-9.01; p0.0001), age50 years (OR, 2.26; p = 0.041), and tumor characteristics.The results of our study have shown that concordance with definitive treatment guidelines was high. However, when current evidence does not support a definitive recommendation for PMRT, treatment decisions appear to be influenced, not only by patient age and clinical characteristics, but also by institution-specific patterns of care.