Capecitabine-related increased mean corpuscular volume of red blood cell may be a predictive marker of treatment response and survival in patients with metastatic colorectal cancer.

Erythrocyte mean corpuscular volume (MCV) increase has been described in patients treated with capecitabine. In this study, we sought to evaluate the potential association of the erythrocyte MCV increase with tumor response and survival in patients with metastatic colorectal cancer (mCRC) treated with capecitabine. A retrospective review of 131 patients with mCRC who were treated with capecitabine for at least 3 months at the Izmir Training and Research Hospital was undertaken. Complete blood count (CBC) including red blood cell indices were recorded at baseline and after 9 weeks from capecitabine treatment. The mean patient age was 57.9 years (range 28- 82). In patients treated with capecitabine, MCV increased significantly at 9 weeks compared with baseline (p=0.000). Median ΔMCV [(post-treatment MCV values) - (baseline MCV values)] level was 9.3 fL. Patients were grouped according to ΔMCV into two groups (> 9.3 or ≥ 9.3) in order to carry out survival analysis and correlation with tumor response. ΔMCV was >9.3 in 65 patients and ≤9.3 in 66 patients. Fifty-six of the 65 patients with ΔMCV levels >9.3 and 37 of the 66 patients with ΔMCV levels ≤9.3 had a clinical benefit (complete response + partial response + stable disease) from capecitabine treatment (p=0.000). The difference between progression-free survival (PFS) and overall survival (OS) of the patients who had ΔMCV>9.3 and those who had ≤9.3 was statistically significant (9.48 and 6.94 months, p=0.001 respectively; and 17.5 and 13.6 months respectively, p=0.018). Univariate analysis suggested that a favorable prognosis for OS and PFS was associated with MCV increase (p=0.000). In multivariate analysis, MCV increase was independently associated with favorable survival outcomes. Erythrocyte MCV increase may be used as a predictive marker for treatment response, PFS and OS in patients with mCRC treated with capecitabine.