Abstract
BACKGROUND: Folate level was proposed to be a predictor for fluoropyrimidine-related toxicity. We conducted a prospective study to determine the association between serum and red-cell folate and capecitabine-related toxicity in patients with colorectal cancers. MATERIALS AND METHODS: Eligibility criteria included diagnosis of colorectal cancers; eligible patients who were scheduled to undergo capecitabine monotherapy or capecitabine-oxaliplatin (CAPOX) for adjuvant or palliative purposes. Exclusion criteria included concomitant radiotherapy or chemotherapy other than capecitabine or CAPOX and creatinine clearance <30 mL/min. Fasting serum and red-cell folate were measured prior to chemotherapy. Capecitabine was administered at 2,500 mg/m(2) per day (monotherapy) or 2,000 mg/m(2) per day (CAPOX) for 14 days every 3 weeks. The toxicity of the first four cycles was documented by clinical investigators who were blinded to folate levels. RESULTS: A total of 144 patients were recruited, of whom 126 were eligible; 40 patients had capecitabine alone, and 86 patients received CAPOX. The rates of grade 2 and grade 3 toxicity were 63.5% and 14.3%, respectively. Nausea and vomiting were the most common grade ≥2 adverse event (47.7%), followed by hand-foot syndrome (25.4%), diarrhea (23.1%), and neutropenia (22.3%). Combination with oxaliplatin (odds ratio [OR], 2.77; p = .043) and serum folate (OR, 10.33; p = .002) were independent predictors of grade ≥2 toxicity. Red-cell folate was not predictive of toxicity. For every 10 nmol/L increment in serum folate, the risk of grade ≥2 toxicity increased by 9%. CONCLUSION: Serum folate level, but not red-cell folate, was associated with higher rate of grade ≥2 toxicity during capecitabine-based treatment. Excessive folate intake may be avoided before and during capecitabine-based chemotherapy. IMPLICATIONS FOR PRACTICE: This is the first prospective study to evaluate the association between serum folate level and capecitabine-related toxicity in patients with colon cancers. It shows that higher serum folate level is associated with increased risks of moderate to severe toxicity during capecitabine-based treatment. Excessive folate intake should be avoided before and during capecitabine-based chemotherapy.