Increased Mean Corpuscular Volume of Red Blood Cells in Patients Treated with Capecitabine for Advanced Breast and Colon Cancer

Purpose: Capecitabine has demonstrated significant activity in metastatic breast and colorectal cancer. During the course of treatment with capecitabine, we observed that a relevant number of patients developed elevated levels of the mean corpuscular volume (MCV) of red blood cells. Methods: This retrospective analysis reviewed treatment with capecitabine in 35 patients with histologically proven advanced breast and colon cancer. After 9 weeks of treatment, restaging was performed using the criteria proposed by the Committee of the Response Evaluation Criteria in Solid Tumours. Results: Prior to the first cycle of capecitabine treatment, there were no abnormalities in red blood cells, white blood cells, haemoglobin or platelets. The median haemoglobin level prior to the first cycle was 13 g/dl and the MCV (normal range 80-98 fl) was 86.5 fl in colon cancer patients and 12.8 g/dl and 88.7 fl in breast cancer patients, respectively. During the course of treatment, 12 weeks after the baseline evaluation, an increase in MCV was documented, while haemoglobin levels remained stable. An MCV increase was documented between baseline and the end of treatment. We noticed an increase in MCV at the end of treatment both in patients with stable disease or a partial response (n = 17) compared to patients with tumour progression (n = 11) at the first evaluation (12-14 weeks). Discussion: Preliminary results showed that there is a significant MCV increase in patients receiving capecitabine for metastatic colon and breast cancer after 12 weeks of treatment. However, when we compared the MCV rise after 12 weeks that occurred with stable disease or a partial response compared to that in patients with disease progression at the first evaluation, the analysis was not statistically significant.