Neoadjuvant cisplatin for head and neck cancer: Simulation of a novel schedule for improved therapeutic ratio

Current clinical studies support the role of neoadjuvant cisplatin administration prior to curative radiotherapy or radio-chemotherapy for advanced head and neck cancer. Nevertheless, based on locoregional control rates the studies indicate that there is need to redesign cisplatin-based schedules for induction chemotherapy, thus the ideal treatment regimen is yet to be established. While the pharmacokinetics/dynamics of daily cisplatin regimens correspond better with the cell cycle properties of head and neck cancers, weekly regimens are more commonly employed in clinics due to lower complications. Yet, the high rates of adverse events induced by current cisplatin schedules often represent a limiting factor in the overall success of the treatment. The aim of the present paper was to model the pharmacodynamic properties of cisplatin and to simulate and compare various neoadjuvant treatment regimens in regards to their effect on tumour control. Treatment simulation was undertaken on a virtual squamous cell carcinoma of the head and neck, previously grown by computer-based probabilistic methods. The model suggests that a novel cisplatin treatment, given every three days is comparable, in regards to tumour control, with the daily administration and more effective than the weekly regimen in neoadjuvant settings. Endpoints were assessed in terms of cell population regrowth after treatment cessation followed by two weeks of unperturbed growth. Simulation of two weeks low-dose daily cisplatin followed by two weeks 'free growth' lead to 15% population regrowth, while weekly high-dose cisplatin over three weeks, followed by two weeks unperturbed growth resulted in 52% tumour cell regrowth. The proposed novel schedule of low-dose third-daily cisplatin gives closer tumour regrowth to daily administration (27% versus 15%) than to the weekly regimen (52%) and also similar cell distribution along the cell cycle as the daily one, suggesting therefore comparable response to subsequent treatment. The advantage of using a third-daily drug regimen would be a decrease in normal tissue complication rates compared to daily administration and possibly an increase in tumour control when compared to the 'conventional' weekly cisplatin delivery.