Impact of disseminated tumor cells in the bone marrow on survival and disease progression in patients with left-sided colorectal cancer.

Introduction: Disseminated tumor cells (DTCs) are a subset of circulating tumor cells that migrate to the bone marrow. Colorectal cancer is a heterogeneous disease depending on the site of the primary tumor.

Objectives: We aimed to assess the association between the presence of DTCs in the bone marrow and tumor characteristics as well as long‑term treatment outcomes in patients with left‑sided colorectal cancer.

Patients And Methods: This prospective study included 91 patients with left‑sided colorectal cancer (37 with colon cancer and 54 with rectal cancer) treated between 2007 and 2012 in a single tertiary center. Fifteen patients had stage I cancer; 26, stage II; 26, stage III; and 24, stage IV. Overall survival and cancer relapse rates were compared between patients with different cancer stages and DTC status.

Results: Bone marrow DTCs were identified in 42 patients (46.1%). The prevalence of DTCs was not related to tumor infiltration depth, nodal involvement, distant metastasis, tumor stage, or primary tumor site. The 5‑year overall survival rates were 59.5% and 53% in the DTC‑positive and DTC‑negative groups, respectively (P = 0.19). There was a notable trend favoring survival in patients with DTCs with stage II and III disease (both separately and when combined). The number of metachronous distant metastases was significantly lower in DTC‑positive patients.

Conclusions: The presence of DTCs in the bone marrow is not associated with primary tumor characteristics and seems to reduce metastasis formation in left‑sided colorectal cancer. There is also a trend for improved overall survival in DTC‑positive patients. These results are intriguing and warrant further confirmation.