Editors' ChoiceBreast Cancer

Circulating Tumor Cells Bad News in Breast Cancer

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Science Translational Medicine  25 Jul 2012:
Vol. 4, Issue 144, pp. 144ec132
DOI: 10.1126/scitranslmed.3004622

Like hunters searching for a bear in the forest, physicians treating patients with breast cancer are always looking for a tell-tale sign, the tracks of the bear. By the time hunters find a broken tree or the remains of half-eaten prey, the bear may be too close, although a lack of these findings does not always indicate a bear-free zone. So it is with breast cancer, for which the currently used signs—tumor size and lymph node metastases—are not always accurate predictors of survival, whereas distant organ metastases are a sign of advanced disease and often untreatable. Even using lymph node metastases, which are currently the best predictor of progression-free survival in patients with early forms of breast cancer, the results are not always accurate. A significant fraction of women without lymph node metastases go on to develop progressive disease, whereas many with lymph node spread remain disease-free. Now, Lucci et al. report a new technique for finding tell-tale tracks of the disease in patients with localized breast cancer, by detecting minute numbers of circulating cancer cells in the patients’ blood.

In order to help predict the patients’ risk of poor outcome and select appropriate therapy, Lucci et al. tested for the presence of circulating tumor cells (CTCs) in blood from over 300 patients with localized breast cancer who were about to undergo surgery. Even one CTC per 7.5 ml of blood conferred a significantly increased risk for tumor progression and worsened overall survival. Moreover, the more CTCs that were detected in the patient’s blood, the worse was her prognosis. The presence or absence of CTCs was a stronger prognostic factor than most of the currently used metrics and was independent of these other features of the tumor, including lymph node status. These results suggest that even in patients who appear to have locally confined breast cancer, the tumor cells can already be spreading through the circulation. This finding indicates that CTCs may help to predict outcomes and distinguish which patients would benefit from additional therapy early in the disease course while avoiding toxic therapies in patients unlikely to benefit.

Although encouraging, the role of CTCs needs to be further evaluated in large, comprehensive clinical trials before it can be used to guide clinical decisions. In the future, if these results are confirmed, perhaps the detection of circulating tumor cells in the blood will help determine the optimal treatment for each patient, and we will get one step closer to tracking that bear.

A. Lucci et al., Circulating tumour cells in non-metastatic breast cancer: A prospective study. Lancet Oncol. 13, 688–695 (2012). [Full Text]

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