Would 1.0 cm be a more suitable cutoff to subdivide pT1 tumors in hormone receptor‐negative and HER2‐positive breast cancer?

BACKGROUND: HER2+ and hormone receptor (HoR)‐negative breast cancer usually associated with poor outcome. However, it remained elusive for the prognosis of small (T1a‐T1c) HER2+/HoR‐ breast cancer. The present study retrospectively analyzed the Surveillance, Epidemiology, and End Results (SEER) database to explore the clinicopathological characteristics and prognosis of T1a‐T1c HER2+/HoR‐ breast cancer. MATERIAL AND METHODS: Data for patients diagnosed with either HER2‐/HoR+or HER2+/HoR‐ T1a‐T1c breast cancer between 2010 and 2012 were obtained from SEER program. Survival analyses were conducted by Kaplan‐Meier method and Cox proportion hazard regression. RESULTS: Totally, 2648 HER2+/HoR‐ and 56387 HER2‐/HoR+T1a‐T1c breast cancer patients were enrolled. There was a clear trend that tumor size had a positive correlation with advanced AJCC stage (P < 0.001) and N‐stage (P < 0.001). T1a and T1b HER2+/HoR‐ breast cancer had great homogeneity in that these two subgroups had comparable survival and both showed no significant survival difference with its counterpart of HER2‐/HoR+subtype. Conversely, T1c HER2+/HoR‐ breast cancers revealed worse prognosis than T1a/T1b HER2+/HoR‐ and T1c HER2‐/HoR+tumors (BCSS HR 3.847, P < 0.001; OS HR 2.055, P < 0.001). CONCLUSION: T1a and T1b HER2+/HoR‐ breast cancer had favorable prognosis and great homogeneity, indicating 1.0 cm may be a suitable cutoff for subclassification of T1 cancer. Future randomized clinical trials were warranted to verify this hypothesis and elucidate the biological behavior of small T1 tumor to facilitate precise medicine.