Fosfomycin does not inhibit the tumoricidal efficacy of cisplatinum

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