This is a radiobiological modelling study aimed at comparing stereotactic ablative body radiotherapy (SABR) with conventional palliative radiotherapy (CPRT) and curative-dose volumetric-modulated arc therapy (CD-VMAT) in the palliation of patients with previously untreated head and neck cancer.

Three radiotherapy plans were generated for 8 patients with head and neck cancer: SABR, prescribed to 45 Gy in 5 fractions; CPRT, prescribed to 30 Gy in 5 fractions and CD-VMAT, prescribed to 70 Gy in 35 fractions. The tumour control probability (TCP) and normal tissue complication probability for salivary and swallowing function (NTCPsaliva and NTCPswallow, respectively) were determined. From those values, the therapeutic ratio, as measured by the uncomplicated tumour control probability (UTCP), was determined.

Dosimetric objectives were achieved in all treatment plans. SABR had a higher mean TCP compared to CPRT and CD-VMAT (100% vs 81% vs 93%, p = 0·003). There were no statistically significant differences in the mean NTCPs for salivary or swallowing function (mean NTCPsaliva 27% vs 41% vs 36%, p = 0·093 and mean NTCPswallow 9% vs 12% vs 23%, p = 0·093). This resulted in the mean UTCP being statistically significantly higher for SABR plans compared to CPRT and CD-VMAT (66% vs 42% vs 49%, p = 0·004).

It is feasible to create SABR plans that satisfy the dosimetric objectives in this study. Based on radiobiological modelling, SABR has superior TCP and similar NTCP, leading to a better therapeutic ratio than CPRT and CD-VMAT.