Importance of circulating tumor cells in newly diagnosed colorectal cancer

Presence of circulating tumor cells (CTC) is associated with poor prognosis in patients with metastatic colorectal cancer (CRC). The present study was conducted to determine if the presence of CTC prior to surgery and during follow‑up in patients with newly diagnosed non-metastatic CRC can identify patients at risk for disease recurrence. In a prospective single center study 183 patients with newly diagnosed non-disseminated CRC, scheduled for surgery, were enrolled and followed-up for a median of 5.1 years. CTC were enumerated with the CellSearch system in 4 aliquots of 7.5 ml of blood before surgery and at several time-points during follow-up after surgery. The results showed that ≥1 CTC/30 ml of blood were detected in 44 (24%) patients before surgery. Patients with CTC before surgery had a significant decrease in recurrence-free survival (RFS, log-rank test p=0.014) and colon cancer related survival (CCRS, p=0.002). The 5-year RFS dropped from 75 to 61% and the 5-year CCRS from 83 to 69% for patients with CTC before surgery. The presence of CTC and positive lymph nodes remained significant factors in multivariate analysis for recurrence-free survival (RFS). Surprisingly, the presence of CTC weeks after surgery was not significantly associated with RFS and CCRD whereas CTC 2-3 years after surgery was again significantly associated with RFS and CCRD. The presence of CTC in patients with stage I-III CRC before surgery is associated with a significant reduction in RFS and CCRS. These findings suggest a role of CTC detection to assess which patients need adjuvant treatment.