Oxygen-Enhanced MRI Detects Incidence, Onset, and Heterogeneity of Radiation-Induced Hypoxia Modification in HPV-Associated Oropharyngeal Cancer

Hypoxia mediates treatment resistance in solid tumors. We evaluated if oxygen-enhanced MRI–derived hypoxic volume (HV_MRI) is repeatable and can detect radiotherapy-induced hypoxia modification in human papillomavirus–associated oropharyngeal head and neck squamous cell cancer.

A total of 27 patients were recruited prospectively between March 2021 and January 2024. HV_MRI was measured in primary and nodal tumors prior to standard-of-care (chemo)radiotherapy and then at weeks 2 and 4 (W2 and W4) into therapy. Two pretreatment scans assessed biomarker within-subject coefficient of variation and repeatability coefficient (RC). Cohort treatment response was measured using mixed-effects modeling. Responding lesions were identified by comparing HV_MRI change with RC limits of agreement.

Oxygen-enhanced MRI identified hypoxia in all lesions. The HV_MRI within-subject coefficient of variation was 24.6%, and RC limits of agreement were −45.7% to 84.1%. A cohort median pretreatment HV_MRI of 11.3 cm³ reduced to 6.9 cm³ at W2 and 5.9 cm³ at W4 (both P < 0.001). HV_MRI was reduced in 54.5% of individual lesions by W2 and in 88.2% by W4. All lesions with W2 hypoxia reduction showed persistent modification at W4. HV_MRI reduced in some lesions that showed no overall volume change. Hypoxia modification was discordant between primary and nodal tumors in 50.0% of patients.

Radiation-induced hypoxia modification can occur as early as W2, but onset varies between patients and was not necessarily associated with overall size change. Half of all patients had discordant changes in primary and nodal tumors. These findings have implications for patient selection and timing of dose de-escalation strategies in human papillomavirus–associated oropharyngeal carcinoma.