Shane R Stecklein1, Xinglei Shen1, Melissa P Mitchell2. 1. Department of Radiation Oncology, University of Kansas Medical Center, Kansas City, KS. 2. Department of Radiation Oncology, University of Kansas Medical Center, Kansas City, KS. Electronic address: mmitchell2@kumc.edu.
Abstract
BACKGROUND: To date, there have been no analyses to assess factors that influence post-mastectomy radiation therapy (PMRT) utilization in invasive lobular carcinoma (ILC) or to quantify the benefit of PMRT in ILC as compared with invasive ductal carcinoma (IDC). We compared histology-specific utilization of PMRT by tumor and patient characteristics and estimated the effect of PMRT on overall and breast cancer-specific survival in ILC and IDC patients meeting American College of Radiology (ACR) criteria for PMRT. PATIENTS AND METHODS: We used the Surveillance, Epidemiology, and End Results database to identify women diagnosed with ILC or IDC from 2004 to 2009 who underwent mastectomy. We assessed utilization of PMRT by T and N stage, analyzed factors associated with PMRT use, and quantified the histology-specific survival benefit of PMRT using log-rank tests and multivariate Cox regression analysis. RESULTS: We identified 86,098 IDC and 12,703 ILC patients. Within this cohort, 18.7% of IDC patients and 26.1% of ILC met ACR criteria for PMRT. Among patients with a definite indication, PMRT was more commonly employed in ILC than in IDC (59.6% vs. 56.3%; P = .0004). Among patients with a definite indication for PMRT, radiation improved 5-year breast cancer-specific survival from 71.4% to 77.0% for IDC (P < .0001) and from 80.9% to 84.7% for ILC (P = .0003). CONCLUSIONS: PMRT was used more commonly in ILC than in IDC. PMRT significantly improves 5-year overall survival and breast cancer-specific survival for ILC patients to a degree comparable with that seen in IDC. Moreover, among ILC and IDC patients who meet ACR criteria, PMRT appears to be significantly underutilized.
BACKGROUND: To date, there have been no analyses to assess factors that influence post-mastectomy radiation therapy (PMRT) utilization in invasive lobular carcinoma (ILC) or to quantify the benefit of PMRT in ILC as compared with invasive ductal carcinoma (IDC). We compared histology-specific utilization of PMRT by tumor and patient characteristics and estimated the effect of PMRT on overall and breast cancer-specific survival in ILC and IDC patients meeting American College of Radiology (ACR) criteria for PMRT. PATIENTS AND METHODS: We used the Surveillance, Epidemiology, and End Results database to identify women diagnosed with ILC or IDC from 2004 to 2009 who underwent mastectomy. We assessed utilization of PMRT by T and N stage, analyzed factors associated with PMRT use, and quantified the histology-specific survival benefit of PMRT using log-rank tests and multivariate Cox regression analysis. RESULTS: We identified 86,098 IDC and 12,703 ILC patients. Within this cohort, 18.7% of IDC patients and 26.1% of ILC met ACR criteria for PMRT. Among patients with a definite indication, PMRT was more commonly employed in ILC than in IDC (59.6% vs. 56.3%; P = .0004). Among patients with a definite indication for PMRT, radiation improved 5-year breast cancer-specific survival from 71.4% to 77.0% for IDC (P < .0001) and from 80.9% to 84.7% for ILC (P = .0003). CONCLUSIONS: PMRT was used more commonly in ILC than in IDC. PMRT significantly improves 5-year overall survival and breast cancer-specific survival for ILC patients to a degree comparable with that seen in IDC. Moreover, among ILC and IDC patients who meet ACR criteria, PMRT appears to be significantly underutilized.