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

PURPOSE: To assess the prognostic and predictive value of circulating tumor cells (CTCs) in metastatic colorectal cancer (mCRC) irrespective of detection level. MATERIALS AND METHODS: We evaluated the prognostic and predictive significance of CTC count at baseline and under treatment in 119 mCRC subjects and compared the standard cutoff (≥3 CTCs/7.5 mL to ≥1 CTCs/7.5 mL). RESULTS: An overall comparison was made between patients with 0, 1-2 and ≥3 CTC (median PFS 8, 4 and 5 months, respectively). Two poor prognostic groups were found, including patients with ≥1 CTCs before and during treatment and patients with 0 CTC at baseline who converted to ≥1 CTCs (p = 0.014). CONCLUSIONS: 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.