Long-term results of T1a, T1b and T1c invasive breast carcinomas in Japanese women: validation of the UICC T1 subgroup classification.

The objectives of this study were to investigate the long-term results of T1a, T1b and T1c Japanese invasive breast cancer patients defined by the UICC classification. The subjects were T1a (38), T1b (256) and T1c (1405) Japanese invasive breast cancer patients. Ten- and 20-year disease-free survival (DFS) and overall survival (OS) rates were analyzed by the UICC T1 subgroups (T1a, T1b, T1c). At 10 years, the respective DFS and OS rates of T1a, T1b and T1c patients were 91.9 and 91.9%, 86.1 and 86.8% and 82.4 and 83.9%, respectively. At 20 years, the respective DFS and OS rates of T1a, T1b and T1c patients were 70.7 and 70.7%, 76.7 and 76.7% and 69.1 and 70.1%. The differences of DFS and OS between T1a and T1c patients were not statistically significant. The DFS of patients with T1c breast carcinoma showed a statistically significant difference from that of T1b patients (p = 0.03). The validation of the T1 subgroup classification in Japanese breast cancer patients was confirmed, particularly for the T1c subgroup.