Impact of Evidence-Based Clinical Guidelines on the Adoption of Postmastectomy Radiation in Older Women

BACKGROUND: Although postmastectomy radiation therapy (PMRT) improves survival for patients with high-risk breast cancer, previous literature suggested that it is underused. The impact of recent clinical guidelines on PMRT use is unknown. Accordingly, the authors used the Surveillance, Epidemiology, and End Results (SEER)-Medicare cohort to determine whether the use of PMRT has increased in response to evidence-based guidelines. METHODS: In total, 38,322 women aged >= 66 years who underwent mastectomy for invasive breast cancer between 1992 and 2005 were identified. Time trends in the receipt of PMRT for low-risk (T1/T2 N0), intermediate-risk (T1/T2 N1), and high-risk (T3/T4 and/or N2/N3) patients were characterized. Multivariate logistic regression identified risk factors for PMRT omission. RESULTS: The receipt of PMRT by patients with high-risk breast cancer increased from 36.5% (95% confidence interval, 26%-46.9%) to 57.7% (95% confidence interval, 46.9%-68.4%) between 1996 and 1998 with the publication of landmark clinical trials. However no further increase in PMRT use was observed between 1999 and 2005 despite publication of multiple guidelines endorsing its use; during this period, only 54.8% (2729 of 4978) of high-risk patients received PMRT. Within this high-risk group, patients with smaller tumors or less advanced lymph node disease were at risk for PMRT omission. CONCLUSIONS: After an initial increase in PMRT use in response to clinical trials, the use of PMRT did not increase further in response to guideline publication, and nearly 50% of patients with high-risk breast cancer still do not receive PMRT. Additional research is needed to determine how clinical guidelines can be used to bridge the gap between level I evidence and clinical practice. Cancer 2011;117:4595-605. (C) 2011 American Cancer Society