Pilot study of PALA and 5-FU in patients with advanced cancer

A pilot study was carried out among 21 patients with advanced solid tumors to establish appropriate dose levels of PALA and 5-FU given on a 5-day schedule to produce definite but tolerable clinical toxicity. While dermatitis, diarrhea, leukopenia, and thrombocytopenia were observed, stomatitis was the dose-limiting side effect. The recommended initial dose levels for further clinical trials are 625 mg/m2 of PALA daily x 5 and 250-300 mg/m2 of 5-FU daily x 5, with courses repeated at 4-week intervals. Studies were also conducted to establish the time course of anticipated increased incorporation of 5-FU into cellular RNA following treatment with PALA. In murine P388 leukemia, PALA increased tritiated 5-FU incorporation by as much as 70%, the effect being maximal within 1 hour and maintained up to 25 hours. It was not possible to demonstrate increased tritiated 5-FU uptake into normal human leukocyte RNA from patients receiving combination chemotherapy with PALA and 5-FU, perhaps because of low rates of RNA synthesis.