A recent study published in Oncologist suggests that circulating tumor cell (CTC) counts are a strong predictor of progression-free survival (PFS) and overall survival (OS) prognosis in patients with metastatic colorectal cancer. The Colorectal Cancer Maintenance Trial is a phase III clinical trial to evaluate bevacizumab monotherapy versus bevacizumab + chemotherapy in patients with metastatic colorectal cancer. An adjuvant study evaluated the value of CTC counts as a prognostic and/or predictive marker for the efficacy endpoint. 180 patients were enrolled. Blood samples were obtained at baseline and after 3 cycles of treatment.CTC counts were measured using the CellSearch system.CT scans were used to assess tumor remission at cycles 3 and 6 and every 12 weeks thereafter. Results showed that patients with baseline CTC counts ≥3 and <3 had a median PFS time of 7.8 and 12.0 months, respectively (P=0.0002), and a median OS time of 17.0 and 25.1 months, respectively (P=0.0059). After 3 cycles of treatment, the median PFS time was 10.8 months in patients with small CTC counts, significantly longer than 7.5 months in patients with large CTC counts (P=0.005); the median OS time was significantly longer in patients with CTC counts <3 than in patients with ≥3, 25.1 and 16.2 months, respectively (P=0.0095).