Overall Survival and Cause-Specific Mortality of Patients With Stage T1a,bN0M0 Breast Carcinoma

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Abstract
Purpose: With mammographic screening, the frequency of diagnosis of stage T1a,bN0M0 breast cancer has increased. Prognosis after locoregional therapy and benefit from adjuvant systemic therapy are poorly defined. We reviewed T1a,bN0M0 breast cancer cases registered in the Surveillance, Epidemiology, and End Results (SEER) Program to investigate the impact of prognostic factors on breast cancer–specific (BCSM) and non–breast cancer–related mortality. Methods: We identified T1a,bN0M0 breast cancer cases registered in the SEER Program from 1988 to 2001, and used the Kaplan-Meier product limit method to describe overall survival (OS). We estimated the probabilities of death resulting from breast cancer and from other causes, and analyzed associations of patient and tumor characteristics with OS, BCSM, and non–breast cancer–related mortality using the log-rank test, Cox proportional hazards models, and a competing-risk model. We constructed nomograms to assist physicians in adjuvant therapy decision making. Results: We identified 51,246 T1a,bN0M0 cases. Median follow-up was 64 months (range, 1 to 167 months). Median age at diagnosis was 65 years (range, 20 to 101 years). Ten-year probabilities of all-cause mortality and BCSM were 24% and 4%, respectively. Characteristics associated with increased probability of BCSM included age younger than 50 years at diagnosis, high tumor grade, estrogen receptor–negative status, progesterone receptor–negative status, and fewer than six nodes removed at axillary dissection. The constructed nomograms allow a comparison of predicted breast cancer–specific survival and non-breast cancer–specific survival in individual patients. Conclusion: Overall, the prognosis of patients with T1a,bN0M0 breast cancer is excellent. However, subgroups of patients who are at higher risk of BCSM and who should be considered for adjuvant systemic therapy can be identified.