Urban and non-urban disparities in the use of post-mastectomy radiation for breast cancer

Post-mastectomy radiation therapy (PMRT) is indicated for local-regionally advanced breast cancer (LABC). We hypothesized that candidates for PMRT from non-urban areas would receive lower rates of RT than urban patients and would have poorer overall survival (OS) and disease-specific survival (DSS). We used the Surveillance, Epidemiology, and End Results database to identify patients diagnosed with LABC and treated with mastectomy in Sacramento and its surrounding 13 counties between 2000 and 2006. All patients were eligible to receive RT according to established guidelines, with tumors >5 cm size, ≥4 metastatic lymph nodes, or both. According to a United States Department of Agriculture scale, we designated counties as urban or non-urban and used multivariate logistic regression and Cox proportional hazards models to predict the use of RT, overall survival (OS), and disease-specific survival (DSS). Density of radiation oncologists in non-urban and urban counties was determined using the American Medical Association database in relation to census-derived populations of the respective counties. Entry criteria were met by 1,507 patients. Most (56.5%) were from urban counties; only 61% received RT. There was no radiation oncologist listed for 8/10 non-urban counties and 2/4 urban counties. Each radiation oncologist served 88,804 people in non-urban counties and 68,624 residents in urban counties. On multivariate analysis, non-urban patients (OR 0.56, CI 0.44–0.72) and increasing age were the only factors predicting a decreased likelihood of receiving RT (OR 0.97, CI 0.96–0.98). Patients not receiving PMRT experienced poorer OS (HR 1.77, CI 1.39–2.25; P < 0.001) and DSS (HR 1.62, CI 1.23–2.15; P = 0.001); however, non-urban status did not predict OS or DSS. Non-urban residents with LABC are less likely to receive indicated PMRT. This discrepancy may be due to limited RT access in non-urban areas. The lack of poorer OS and DSS due to this disparity requires further study.