Micrometastases in sentinel lymph nodes: few data make for hard decisions.

O ver the past 10 years, breast cancer researchers have debated the tricky question of what to do when a pathologist finds micrometastases or isolated tumor cells in the sentinel lymph node. Their conflicting opinions have left many physicians questioning whether to proceed with the axillary lymph node dissection (ALND), which removes all remaining axillary lymph nodes, or to skip the operation and spare the patient its potential side effects. A group of Dutch researchers recently came down on one side of the debate. Published in the August 13 issue of the New England Journal of Medicine , their study found that patients with micrometastases left untreated had a substantially higher 5-year risk of recurrence than did node-negative patients, who also did not receive adjuvant therapy. “In patients with micrometastases in the sentinel node, we advise complete [ALND],” said Vivianne C. Tjan-Heijnen, M.D., Ph.D. , head of the division of medical oncology at Maastricht University Medical Center in The Netherlands, who presented the data from the New England Journal of Medicine study at the annual meeting of the American Society of Clinical Oncology (ASCO). Tjan-Heijnen pointed out that in this study, even among patients whose primary tumors had favorable characteristics, such as being smaller than 3 cm, and even including patients given adjuvant therapy, the risk of axillary recurrence was about 5% for women with micrometastases, compared with 1% for those who had ALND or axilla radiotherapy. The sentinel lymph node, which is the fi rst node that lymph fl uid enters after draining from the breast, is the most common site of breast cancer metastasis, and patients who are node negative — meaning that the biopsy turns up no cancer in the sentinel node — have a better prognosis than those who are node positive. Under present U.S. guidelines, patients with micrometastases, which range from 0.2 mm to 2.0 mm, are considered to be node positive, and some experts say they should be treated as all other node-positive patients: Their biopsy should be followed by an ALND. However, in about 40% – 60% of nodepositive patients, no cancer will be found in any other axillary nodes. That means, say some experts, that the ALND can be safely avoided altogether in some patients. Answers to this confounding question do not seem to be forthcoming — trials done thus far are retrospective and the results are mixed. And existing imaging techniques do not hold hope for revealing cancers this tiny. So physicians and patients may be left to weigh the cost and benefi ts of proceeding with ALND for some time.