Circulating tumor cells in metastatic colorectal cancer: do we need an alternative cutoff?

To assess the prognostic and predictive value of circulating tumor cells (CTCs) in metastatic colorectal cancer (mCRC) irrespective of detection level. We evaluated the prognostic and predictive significance of CTC count at baseline and under treatment in 119 mCRC subjects and compared the standard cutoff (a parts per thousand yen3 CTCs/7.5 mL to a parts per thousand yen1 CTCs/7.5 mL). An overall comparison was made between patients with 0, 1-2 and a parts per thousand yen3 CTC (median PFS 8, 4 and 5 months, respectively). Two poor prognostic groups were found, including patients with a parts per thousand yen1 CTCs before and during treatment and patients with 0 CTC at baseline who converted to a parts per thousand yen1 CTCs (p = 0.014). The presence of at least 1 CTC at baseline count is predictive for poor prognosis in mCRC patients. Patients with 1-2 CTC should be switched from the favorable prognostic group-conventionally defined by the presence of < 3 CTC-to the unfavorable, deserving a more careful monitoring.