Prognostic factors of T 1 a-T 1 b breast cancer : a retrospective cohort study

Objectives: We aimed to analyze the clinicopathological features and prognostic factors of breast cancer patients with T1a-T1b, which was defined as tumor size was within 1 cm. Methods: From the Surveillance, Epidemiology, and End Results (SEER) database, we identified 39143 patients with T1a-T1b breast cancer who were diagnosed from January 1, 2010 to December 31, 2013. Clinicopathological features and prognosis were analyzed. Outcomes for breast cancer-specific survival (BCSS) and overall survival (OS) were estimated using the KaplanMeier method and compared using the log-rank test. Cox proportional hazards models were used to determine independent factors relating to prognosis. Results: There were 10966 T1a and 28177 T1b breast cancer patients. The median follow-up was 15.78±10.54 months. The overall mortality rate was 1.38% (541/39143), and the breast cancer related mortality rate was 0.28% (108/39143). Multivariate analysis showed that age, histological grade, distant metastasis, HR status, surgery, and radiotherapy were independent factors of BCSS, while age, distant metastasis, HR status, surgery, and radiotherapy were independent factors of OS. Triple-negative breast cancer had a significantly poorer survival than the other three patient subgroups (P<0.001). Surgical approach (breastconserving surgery or mastectomy) was unrelated to prognosis in T1a-T1b patients. Radiotherapy had a beneficial effect on both T1a-T1bN0 and T1a-T1bN1 patients who underwent mastectomy. Conclusion: Larger tumor size, HRand Her-2+ status were associated with more aggressive tumor behavior. More aggressive treatment should be performed for T1a-T1b breast cancers with these prognostic risk factors: young age, high histological grade, distant metastasis, and HR-status, especially for triple-negative breast cancer. Breast-conserving surgery should be performed more commonly at the global level. Radiaotherapy should be considerable for T1a-T1b N0-N1 breast cancers even when mastectomy were performed.