Hypocalcemia associated with 5-fluorouracil and low dose leucovorin in patients with advanced colorectal or gastric carcinomas

BACKGROUND: The biochemical modulation of 5-fluorouracil (5-FU) by leucovorin (LV) has demonstrated significantly increased response rates in comparison with the use of 5-FU alone in patients with advanced colorectal carcinoma. However, the higher response rate of LV/5-FU may occur at the expense of increased toxicity and side effects such as diarrhea, myelosuppression, and mucositis. During chemotherapy, a high incidence of hypocalcemia associated with this chemotherapy regimen was noted. This study was therefore aimed at assessing the side effects of chemotherapy using low dose LV/5-FU on calcium metabolism. METHODS: Twenty-five patients with advanced gastric or colorectal carcinoma were treated with chemotherapy comprised of low dose LV administered at 20 mg/m2/ day by intravenous bolus, followed by 1-hour intravenous infusion of 5-FU at 425-600 mg/m2/day for 5 consecutive days every 28 days. RESULTS: The toxic effects were generally mild, and included diarrhea, mucositis, leukopenia, and nausea/vomiting. Fifteen patients (65%) experienced hypocalcemia. The plasma 1,25-(OH)2D3 levels were significantly reduced on Day 5 due to the chemotherapy. CONCLUSIONS: The toxic effects of the regimen were generally mild. However, a high percentage of hypocalcemia occurred with the combination of LV/5-FU. It is therefore necessary to examine carefully the serum calcium levels of patients when using this chemotherapeutic modality.