A new review and meta-analysis of previously published studies has found that micrometastases of 2 mm or less in diameter in axillary lymph nodes predicts increased breast cancer recurrence rates and reduced survival. The prognostic significance of isolated tumor cells and micrometastases in lymph nodes in breast cancer patients has become important since the introduction of the sentinel lymph node procedure. The authors included 58 studies with 297,533 participants published between 1997 and 2008 in the review. Cohort studies with single-section pathological examination of axillary lymph nodes (285,638 total patients) and occult metastases studies with retrospective examination of negative lymph nodes (7,740 patients) were fully analyzed. Sentinel lymph node biopsy studies with intensified work-up of the sentinel node (4,155 patients) were also reviewed, however this analysis was hampered by small patient groups and short follow-up periods.

In the cohort studies, the presence (compared to the absence) of metastases of 2 mm or less in diameter in axillary lymph nodes was found to be associated with a 44% greater risk of death. In the occult metastases studies, the presence (compared to the absence) of occult metastases was found to be associated with a 55% greater risk of recurrence during the first five years, as well as a 45% increased risk of death. However, note that disease-free survival and overall survival were not consistently assessed in the reviewed studies. The authors conclude that the presence of metastases of 2 mm or less in diameter in axillary lymph nodes detected on single-section examination was associated with poorer disease-free and overall survival compared to the absence of such micrometastases.

Study implies that lymph node micrometastases be treated

The study results imply that it is important that micrometastases and isolated tumor cells be detected when axillary lymph nodes are examined. Furthermore, breast cancer patients with such findings should receive appropriate adjuvant treatment (such as chemotherapy) in addition to radiation even if the primary tumor is small.