Contralateral Axillary Lymph Node Metastases from Breast Carcinoma: Is it Time to Review TNM Cancer Staging?

Background: Contralateral axillary lymph node metastasis (CAM) is an infrequent clinical condition currently considered an M1, stage IV, disease. Due to the absence of shared data on CAM significance and on its therapeutic approach, be it curative or simply palliative, its management is still uncertain and undoubtedly represents a clinical challenge. Patients and Methods: Patients with pathologically confirmed metachronous CAM were retrospectively evaluated. All patients had been managed at the European Institute of Oncology, Milan, Italy, from 1997. Patients with distant metastases at the time of CAM were excluded. Possible treatments included surgery, systemic therapy and RT (radiotherapy). Outcomes were evaluated as rates of disease-free survival (DFS) and of overall survival (OS). Results: Forty-seven patients with CAM were included in the study. Metachronous CAM occurred 73 months (range 5–500 months) after diagnosis of the primary tumor. The median follow-up time was 5.4 years (interquartile range 2.9–7.0 years). The estimated OS was 72% at 5 years (95% CI 54–83), and 61% at 8 years (95% CI 43–75). The estimated DFS was 61% at 5 years (95% CI 44–74), and 42% at 8 years (95% CI 25–59). Conclusion: These findings, together with those from previous studies, show that CAM outcome, particularly if measured as OS, appear better than at other sites of distant dissemination, when CAM is subjected to surgical and systemic treatments with a curative intent. Therefore, a new clinical scenario is suggested where, in the TNM system, CAM is no longer classified as a stage IV, but as an N3 disease.