Fosfomycin does not inhibit the tumoricidal efficacy of cisplatinum

Objectives: This study investigates the effect of fosfomycin on the tumoricidal efficacy of cisplatinum. Study Design: Prospective study utilizing the FaDu squamous cell carcinoma cell line and a nude mouse tumor xenograft model. Methods: Tumor cell growth was assessed in vitro in the presence of cisplatinum and/or fosfomycin utilizing the MTT assay. An optimal cisplatinum dose and dosing schedule was established in a nude mouse tumor xenograft model of squamous cell carcinoma. Using this model, fosfomycin was tested at three dosages and tumor growth monitored over 4 weeks. Results: Mice treated with cisplatinum and fosfomycin had smaller tumors than those treated with cisplatinum alone (P < .01). Conclusions: This study is the first demonstration that fosfomycin does not inhibit the tumoricidal efficacy of cisplatinum in vivo. This suggests that fosfomycin may be useful in preventing cisplatinum-induced ototoxicity and nephrotoxicity in humans without altering the tumor response rate.