9: Radiation Use and Long-Term Survival in Breast Cancer Patients With T1,T2 Primary Tumors and 1-3 Positive Axillary Lymph Nodes

Abstract

For patients with Stage II breast cancer with 1-3 positive lymph nodes, controversy exists as to whether radiation as a component of treatment provides a survival benefit. A previous comparison of patients treated with or without radiation after mastectomy using Surveillance, Epidemiology, and End Results (SEER) data did not find radiation use to be associated with an improved survival for this cohort of patients ((1)Smith B.D. Smith G.L. Haffty B.G. Postmastectomy radiation and mortality in women with T1-2 node-positive breast cancer.J Clin Oncol. 2005; 23: 1409-1419Crossref PubMed Scopus (36) Google Scholar). However, despite being appropriately analyzed, it is likely that a number of biases affected these results. To further examine this question, we compared the long-term outcome of patients with Stage II breast cancer with 1-3 positive lymph nodes who were treated with radiation as a component of breast conservative treatment (BCT + XRT) to patients with this stage of disease who were treated with mastectomy and no radiation (MRM w/o XRT). We analyzed the SEER registry of breast cancer patients diagnosed between 1988-2002 and identified 12,693 patients who were treated with BCT + XRT and 18,902 patients who were treated with MRM w/o XRT for a stage II breast cancer with 1-3 positive lymph nodes. Breast cancer-specific survival and overall survival rates were calculated using the Kaplan Meier method; a multivariable analysis was performed using the Cox regression model. Patients treated with BCT + XRT were more likely to be treated in the more recent years of the study period (median treatment year 1998 vs. 1995), were younger (median age 55 vs. 60), had smaller primary tumors (T2 tumors 34% vs. 49%), and had fewer involved nodes (rates of 1 positive lymph node 66% vs. 51%) compared to those treated with MRM w/o XRT (p<0.001 for all differences). The 15-year breast cancer specific survival for the BCT +RT group was 80% vs. 72% for the MRM w/o RT (p<0.001). Overall survival was also significantly better in the BCT + RT group. Cox regression analysis showed that MRM w/o XRT was associated with a hazard ratio for breast cancer death of 1.187 (p<0.001) and for overall death of 1.249 (p<0.001). The survival benefit in BCT + RT group was not limited to those subgroups with higher risk features (younger age, high grade, increasing T stage or increasing number of involved lymph nodes). Patients with Stage II breast cancer with 1-3 positive lymph nodes who were treated with treated with BCT + XRT had a better breast cancer specific and overall survival than those treated with MRM w/o XRT. Our data suggests an independent association between radiation use and an improved survival in this cohort. However, because multivariate analyses of retrospective data cannot account for all potential biases, these data should be confirmed by randomized clinical trials.