Background: Mammography screening usually detects low-risk breast cancer in the western world. However, little is known about the ultrasound and mammography screen-detected T1 invasive non-palpable breast cancer (NPBC) in asymptomatic Chinese women.
Results: With the increase of tumor size (T1a, b, c), lymph node positivity (8.7%, 18.3%, 26.0%, p = 0.018), pN (p = 0.028) and TNM stage (p = 0.035) increased accordingly. Tumor size (T1a, b, c) was correlated with high Ki-67 index (defined as ≥ 14%, 37.9%, 45.8%, 56.2%, p = 0.017), chemotherapy (20.4%, 35.2%, 57.3%, p < 0.001) and targeted therapy (2.9%, 9.9%, 15.1%, p = 0.008). T1a disease had higher chance of being luminal A and accompanied with ductal carcinoma in situ (DCIS), while T1c tumor being triple-negative and without DCIS. The 5-year disease free survival (DFS) of T1a, b, c NPBC were 99.0%, 96.9% and 92.9%, whereas the 5-year overall survival (OS) were 100.0%, 100.0% and 97.9% respectively. There was no significant difference in 5-year DFS or OS among the T1 NPBC subgroups or subtypes/immunophenotypes.
Patients and methods: From 2001 to 2014, 4,574 screening positive women received biopsies in Peking Union Medical College (PUMC) Hospital, and 729 NPBC including 437 T1 unilateral invasive NPBC were diagnosed. With a median follow-up time of 32 months (6-163 months), the clinicopathological characteristics, treatment choice, 5-year DFS and OS were compared between T1a, T1b and T1c NPBC. The DFS and OS prognostic factors were identified.
Conclusion: Screen-detected T1 invasive NPBC could be regarded as low-risk cancer in Chinese women. TNM stage and LN metastasis instead of molecular subtype was identified as the DFS prognostic factors while radiotherapy as the OS predictor.
Keywords: T1; lymph node metastasis; non-palpable breast cancer; prognosis; screen-detected breast cancer.