Do lymph node micrometastases and isolated tumor cells influence survival in breast cancer patients?

In this study, researchers evaluated whether isolated tumor cells (ITC) or micrometastases can predict survival in breast cancer patients and whether there is need for additional treatments in these patients.

After surgery to treat breast cancer, many patients undergo a sentinel node biopsy (SNB). SNB is the microscopic examination of lymph node cells to determine whether breast cancer has spread (metastasized) to the nearby lymph nodes. This exam will indicate whether a lymph node is cancer-free (node-negative), has a few cancerous cells (ITC), or has a small tumor that can only be seen under a microscope (micrometastasis). Although it is well known that lymph node invasion is a strong prognostic factor for breast cancer patients and needs aggressive therapy, it is not clear whether ITC and micrometastases are related to poorer outcomes in these patients. Therefore, it is important to understand the risks they indicate, so doctors may follow with the appropriate therapy.

This study included 18,370 patients from the Netherlands Cancer Registry. All patients had small tumors (less than T3) and their SNB was labeled either node-negative (cancer-free lymph nodes), ITC, or micrometastases. Overall, disease-free survival or DFS (the time a patient survives after treatment without any signs or symptoms of the disease), was not different between the 3 groups. However, the results of the SNB influenced treatment. Node-negative patients were more likely to have breast conserving treatment (surgery to remove the cancer plus radiotherapy), while patients with ITC and micrometastases were more likely to have all lymph nodes removed and to receive additional (adjuvant) chemotherapy and hormonal treatment. When DFS was corrected for each of these treatments, the authors found that node-negative and ITC patients had equal survival rates, but patients with micrometastases were 38% more likely to develop a recurrence (return of the cancer) within 5 years after diagnosis.

In summary, node-negative breast cancer patients and those with ITC lymph nodes had similar outcomes, but patients with lymph node micrometastases were more likely to develop a recurrence. This study also showed that all patients benefitted from adjuvant therapies (chemotherapy and hormonal therapy). This was particularly true for patients with micrometastases, who eventually had similar survival as patients with ITC and node-negative.