Circulating Tumour Cell Levels Forecast Metastatic Breast Cancer Survival

Circulating tumour cell levels may predict the survival of patients undergoing first-line chemotherapy for metastatic breast cancer

medwireNews: Measuring Circulating tumour cell (CTC) levels after first-line chemotherapy for metastatic disease may indicate prognosis in breast cancer patients, phase III study findings suggest.

The research, reported at the 55th San Antonio Breast Cancer Symposium in Texas, USA, showed that overall survival (OS) was highest in the 276 patients who had fewer than 5 CTC per 7.5 mL of whole blood at baseline, at a median of 35 months.

By comparison, OS was significantly lower, at a median of 23 months, for the 163 women who had elevated CTCs at baseline but whose CTC level was below the 5 CTC per 7.5 mL threshold at day 21 of chemotherapy, and lowest for the 123 patients who continued to have elevated CTCs at day 21, at a median of 13 months.

“This suggests that chemotherapy may not be as effective for these cancers in which CTCs remain elevated after one cycle of chemotherapy,” said presenting author Jeffrey Smerage, from the University of Michigan in Ann Arbor, USA, in a press release.

“This doesn’t mean that chemotherapy has no benefit, but it suggests that the benefit is limited.”
The partially randomised SWOG S0500 trial for patients with measurable metastases including bone disease also found that participants with persistently elevated CTCs at day 21 did not benefit from switching chemotherapy regimens at this point.

“It had been hoped that switching would both increase the chances of being on an effective therapy and decrease the exposure to toxicity from less effective or ineffective therapies, and as a result it had been hoped that this early switching would result in improved survival and time to progression,” explained Jeffrey Smerage.

However, the 64 patients who continued with their original cytotoxic therapy had overall and progression-free survival rates of 3.5 and 12 months, compared with 4.6 and 12 months for the 57 patients who switched to a second cytotoxic regime.

“We concluded that CTCs are not a good marker in helping to decide when to switch between chemotherapies,” said Jeffrey Smerage.


55th San Antonio Breast Cancer Symposium; Texas, USA: 10–14 December 2013

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