Comparison of intravenous and oral high-dose methotrexate in treatment of solid tumours.

An outpatient regimen of oral high-dose methotrexate was studied in 14 patients with solid tumours over 12 months. Detailed pharmacokinetic analysis in five patients showed high oral bioavailability (mean +/- SE of mean 87.6 +/- 1.5%), indicating that with this regimen oral methotrexate was well absorbed and the first-pass effect low. Oral administration resulted in peak plasma methotrexate concentrations of 8.4 +/- 0.5 mumol/l (382 +/- 23 microgram/100 ml) and was almost as effective as intravenous administration, which achieved peak concentrations of 9.9 +/- 0.4 mumol/l (450 +/- 18 microgram/100 ml). In all 14 patients the clinical response to oral treatment was comparable to that reported to intravenous administration of high-dose methotrexate used in combination with other cytotoxic drugs. The disease-free interval in cases of adult sarcoma was 7.4 +/- 1.3 months and the relapse rate 29%. Out of four patients with small-cell carcinoma, two showed an objective response to oral treatment. We suggest that oral high-dose methotrexate given in divided doses is a rational alternative to expensive intravenous high-dose methotrexate regimens, but further clinical evaluation is necessary.