The Preoperative Peripheral Blood Monocyte Count Is Associated with Liver Metastasis and Overall Survival in Colorectal Cancer Patients

Background Colorectal cancer (CRC) is the third most common malignancy in males and the second most common in females worldwide. Distant metastases have a strong negative impact on the prognosis of CRC patients. The most common site of CRC metastases is the liver. Both disease progression and metastasis have been related to the patient's peripheral blood monocyte count. We therefore performed a case-control study to assess the relationship between the preoperative peripheral blood monocyte count and colorectal liver metastases (CRLM). Methods Clinical data from 117 patients with colon cancer and 93 with rectal cancer who were admitted to the Chinese People's Liberation Army General Hospital (Beijing, China) between December 2003 and May 2015 were analysed retrospectively, with the permission of both the patients and the hospital. Results Preoperative peripheral blood monocyte counts, the T and N classifications of the primary tumour and its primary site differed significantly between the two groups (P < 0.001, P < 0.001, P = 0.002, P < 0.001), whereas there were no differences in the sex, age, degree of tumour differentiation or largest tumour diameter. Lymph node metastasis and a high preoperative peripheral blood monocyte count were independent risk factors for liver metastasis (OR: 2.178, 95% CI: 1.148 similar to 4.134, P = 0.017; OR: 12.422, 95% CI: 5.076 similar to 30.398, P < 0.001), although the risk was lower in patients with rectal versus colon cancer (OR: 0.078, 95% CI: 0.020 similar to 0.309, P < 0.001). Primary tumour site (P<0.001), degree of tumour differentiation (P = 0.009), T, N and M classifications, TNM staging and preoperative monocyte counts (P<0.001) were associated with the 5-year overall survival (OS) of CRC patients. A preoperative peripheral blood monocyte count > 0.505 x 10(9) cells/L, high T classification and liver metastasis were independent risk factors for 5-year OS (RR: 2.737, 95% CI: 1.573 similar to 4.764, P <0.001; RR: 2.687, 95% CI: 1.498 similar to 4.820, P = 0.001; RR: 4.928, 95% CI: 2.871 similar to 8.457, P < 0.001). Conclusions The demonstrated association between preoperative peripheral blood monocyte count and liver metastasis in patients with CRC recommends the former as a useful predictor of postoperative prognosis in CRC patients.