Global Dose Prescription Variances Exemplified Through Oropharynx Cancer: When Is 70 Gray 70 Gray?

Radiation therapy treatment planning hinges on a critical factor: the prescribed dose. Surprisingly, there is no consistent, standardized global approach to evaluating the dosimetry of this prescription across different centers treating head and neck cancer (HNC). This study aimed to quantify global dose variations for identical prescriptions across international centers treating oropharyngeal cancer, to establish the foundation for future outcome-based studies and improve consistency of interpretation worldwide.

The study included patients with oropharyngeal cancer who were consecutively treated from 2017 onward with intensity-modulated radiation therapy or volumetric modulated arc therapy at 8 globally recognized radiation therapy departments. These centers were categorized into 4 categories: North American, North European, Oceanic, and Asian.

The study included 1514 patients from 8 centers and revealed 40 different dose prescriptions, ranging from 55 Gy in 20 to 70 Gy in 35 fractions. When normalized to a 70 Gy prescription, the mean clinical target volume dose showed a 4% median difference across centers. European and Oceania centers deviated by 0.4%, whereas North American and Asian centers had 2% variability. Near-minimum clinical target volume doses (D_98%) ranged from 68.7 to 71.4 Gy.

The study underscores the wide-ranging implementation of dose prescriptions in HNC. The lack of a standardized global approach to HNC treatment dose prescription carries potential implications for patient care, collaborative research, and treatment de-escalation or radiation therapy dose-painting strategies. This study highlights the need for careful interpretation of dose prescription standards across international centers, to analyze radiation therapy outcomes more accurately in light of their varied implementation.