KEY POINTS
- This prospective single-centre study included 314 patients receiving radiotherapy for breast, prostate, or head-and-neck cancer. Pretreatment microvascular status was assessed non-invasively using sublingual video microscopy.
- Direct MicroVascular Health Score measurement was available in 182 patients. Across the combined population, each 1-point increase in MVHS was associated with lower acute toxicity risk: OR 0.68 (p=0.001), equivalent to a 31.9% higher risk per 1-point decrease.
- Acute side effects occurred in 39% of the full cohort. Event rates were 13.8% for MVHS ≥4.5, 35.0% for MVHS 2–4.5, and 52.0% for MVHS <2 (p=0.01).
- The association was significant in breast cancer (OR 0.61 per 1-point increase; p=0.006) but not in prostate (OR 0.77; p=0.28) or head-and-neck cancer (OR 0.94; p=0.77) when analysed separately.
- In breast cancer, adding MVHS to the best dose-based model increased the AUC from 0.69 to 0.76. Approximately 40% of patients could not complete sufficient imaging for direct MVHS calculation, requiring an imputation strategy.
CLINICAL TAKEAWAY
Pretreatment sublingual microvascular assessment may provide patient-specific information beyond dosimetry when estimating acute radiotherapy toxicity, particularly in breast cancer. However, this remains preliminary biomarker evidence because the study was single-centre, used different toxicity endpoints across disease sites, lacked external validation, and depended on imputed MVHS values for many patients.