Long-term breast cancer survival in relation to the metastatic tumor burden in axillary lymph nodes

Purpose The clinical significance of lymph node micrometastases and isolated tumor cells (ITCs) in breast cancer is still controversial. After a median follow-up of 52 months, a report from the Swedish Multicenter Cohort Study presented a worse cancer-specific and event-free survival for patients with micrometastases than node-negative individuals, but could not demonstrate a significant difference in overall survival (OS). Due to the tendency of breast cancer to relapse after more than 5–10 years, we now report the long-term survival of the cohort. Methods Between September 2000 and January 2004, 3355 breast cancer patients were included in a prospective cohort. Sentinel lymph node biopsy was always performed. Patients were classified in four groups according to their overall nodal stage: node negative (N0, 2372), ITCs (113), micrometastases (123), and macrometastases (747). Kaplan–Meier survival estimates and Cox proportional hazard regression models were applied. Results Median follow-up was 156 months. Ten-year cancer-specific survival and OS were significantly lower in case of micrometastases than in N0 (84.7 vs. 93.5%, p = 0.001, and 75.5 vs. 84.2%, p = 0.046, respectively). In case of macrometastases, corresponding survival rates were 82.8 and 74.3%. Only for those aged less than 50 years, cancer-specific survival and OS were significantly worse in case of ITCs than N0. Patients with micrometastases received less often chemotherapy than those with macrometastases (24.4 vs. 53.9%). Conclusions Lymph node micrometastases in breast cancer have a prognostic significance. This study demonstrates a similar survival for patients with micrometastases and those with macrometastases, possibly due to systemic undertreatment.