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Isolated Tumor Cells and Micrometastases in Breast Cancer

Disease-free survival was diminished in patients with ITCs or micrometastases who did not receive systemic adjuvant therapy.

The association between breast cancer outcomes and presence of isolated tumor cells (ITCs) or micrometastases in regional lymph nodes is unknown. To examine this issue, investigators in the Netherlands conducted a retrospective analysis of 995 node-positive patients (with ITCs or micrometastases) who had received treatment (systemic adjuvant therapy), 856 node-positive patients who had not received treatment, and 856 node-negative patients who had not received treatment.

At median follow-up of 5.1 years, 5-year disease-free survival (DFS) rates were lower both in patients with ITCs and in those with metastases who did not receive treatment than in those with node-negative disease (77.2% and 75.9%, respectively, vs. 85.7%; P<0.001). Results were similar after controlling for rates of axillary therapy (complete dissection or irradiation), which were significantly different among the groups (P<0.001). Treatment was associated with improved DFS in patients with ITCs or micrometastases. Five-year first-event rates of distant metastases were similar between node-positive patients who received treatment and node-negative patients (2.6% and 2.8%).

Comment: These results are important because they clearly show that ITCs identified in axillary lymph nodes are associated with diminished 5-year DFS in women with early breast cancer who did not receive adjuvant systemic therapy. They also show that adjuvant therapy is associated with improved DFS in node-positive patients. More than 70% of women in this study had tumors >1 cm, but only 2.2% of patients received chemotherapy, and only 11.4% received chemotherapy or hormone therapy. Therefore, in patients treated under new guidelines in the Netherlands and in patients in the U.S., where systemic adjuvant therapy is commonly given for breast cancer, the impact of identifying ITCs or micrometastases on DFS will be smaller than that observed in this study. Furthermore, this effect should diminish further, given the availability of better systemic agents (such as taxanes and trastuzumab) and the promise of more-effective drugs now under development. An essential caveat noted by the authors is that no conclusion can be reached about the effects of axillary lymph node dissection on DFS in patients with ITCs or micrometastases. This important issue is being addressed in a clinical trial designed to evaluate sentinel lymph node biopsy without subsequent axillary dissection.

— Henry Mark Kuerer, MD, PhD, FACS

Published in Journal Watch Oncology and Hematology September 15, 2009

Citation(s):

de Boer M et al. Micrometastases or isolated tumor cells and the outcome of breast cancer. N Engl J Med 2009 Aug 13; 361:653.

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