In Vitro Study of the Anti-cancer Effect of Alternate-day 5-Fluorouracil in Head and Neck Cancer Cells.

Background/Aim: We have previously reported that alternate-day S-1 had comparable effects and milder adverse events than the respective consecutive-day regimen in head and neck cancer (HNC) patients. The aim of this study was to investigate the anticancer effects of both regimens and underlying mechanisms in vitro. Materials and Methods: Two head and neck squamous cell carcinoma (HNSCC) cell lines were treated with 5-FU given on an alternate-day or consecutive-day schedule. The relative inhibition (RI) of tumor growth was calculated. Cell cycle distributions and cyclin expression following 5-FU treatment were analyzed. Results: The RI of both regimens was almost identical. The percentage of cells in S phase was significantly increased in the alternate-day group compared to the consecutive-day group (p< 0.001). Conclusion: The cytotoxic effect of alternate-day was equivalent to that of consecutive-day. S-phase arrest was more prominently observed with the alternate-day regimen, which may help maintain 5-FU sensitivity in head and neck cancer cells.