To explore the risk factors and time distribution of recurrence and metastasis in triple negative breast cancer.

We retrospectively analyzed the clinicopathological data and follow-up data of 307 cases of triple negative breast cancer in Cancer Hospital of Chinese Academy of Medical Sciences from January 1, 1998 to December 31, 2008. The categorical variables including age grouping, menstrual status, family history of breast cancer or ovarian cancer, pathological type, tumor size, lymph node metastasis, TNM stage, vascular tumor thrombus, surgical method, lymph node dissection method and radiotherapy were compared between groups using χ² test. Survival curves of invasive disease-free survival were drawn using the Kaplan-Meier method and comparison between groups was performed using log-rank test. In order to correct confounding factors, Cox proportional hazards model was used for multi-factor analysis. Life table method depicted the peak curve of recurrence and metastasis to study the time distribution of recurrence and metastasis in triple negative breast cancer.

By the end of follow-up (median follow-up time of 137 months), a total of 103 cases (33.5%, 103/307) had recurrence and metastasis. The sites of recurrence and metastasis in the initial diagnosis included regional lymph node metastasis (37.9%, 39/103), lung metastasis (32.0%, 33/103), bone metastasis (31.1%, 32/103) and local recurrence (26.2%, 27/103). Univariate analysis showed that TNM stage, tumor size, lymph node metastasis, vascular tumor thrombus and surgical method were the factors affecting recurrence and metastasis of triple negative breast cancer (χ²=27.977, 16.466, 33.993, 7.408, 7.616, all P<0.050). Multivariate analysis showed that lymph node metastasis and modified radical mastectomy were independent risk factors for invasive disease-free survival of triple negative breast cancer (N₁ vs N₀: HR=1.679, 95.0%CI: 1.049-2.687, P=0.031; N₂ vs N₀: HR=2.147, 95.0%CI: 1.205-3.826, P=0.010; N₃ vs N₀: HR=5.071, 95.0%CI: 2.988-8.604, P<0.001; breast conserving surgery vs modified radical mastectomy: HR=0.348, 95.0%CI: 0.128-0.949, P=0.039). The peak curve of the recurrence and metastasis risk of triple negative breast cancer presented a four-peak pattern. Recurrence and metastasis peaks occurred at the 1st, 3rd, 7th and 11th year after surgery. The fourth peak of recurrence and metastasis was more significant in stage N₃ of lymph node metastasis.

Lymph node metastasis and modified radical mastectomy are main risk factors affecting the recurrence and metastasis of triple negative breast cancer. Distinct from other molecular subtypes of breast cancer, triple negative breast cancer shows the four-peak pattern of recurrence and metastasis risk curve. The patients with higher stage of lymph node metastasis are still at high risk of recurrence and metastasis at the 11th year after surgery.