Optimal methionine-free diet duration for nitrourea treatment: a Phase I clinical trial

In animal models, methionine (MET) restriction in association with chloroethylnitrosoureas led to a substantial improvement. On this basis, we initiated a Phase I clinical trial of dietary MET restriction in association with chloroethylnitrosourea (cystemustine) treatment for patients with recurrent glioma or metastatic melanoma. Our purpose was 1) to determine the optimal MET-free diet duration for a maximum depletion of plasma MET and 2) to evaluate the feasibility of this association. A total of 10 patients received 4 cycles of 2 wk of an association of a MET-free diet of 1, 2, 3, or 4 consecutive days and cystemustine (60 mg/m(2)). For each cycle, plasma MET concentrations, nutritional status (weight, albumin, prealbumin) and toxicity were measured. Conversely, fed-state concentrations of plasma MET (12 AM) were reduced by dietary MET restriction, with an optimal depletion of 41% at the 1st day of MET-free diet without effect of the extending MET-free diet period. Indeed, we demonstrated the feasibility, that is, good diet acceptability and good tolerance (nutritional status and toxicity), of the association of a MET-free diet and cystemustine treatment. Based on these results, a Phase II clinical trial has been initiated to test the activity of the association of a 1-day MET-free diet with cystemustine treatment.