KEY POINTS
- This multicentre retrospective study included 337 patients with HPV-positive oropharyngeal squamous cell carcinoma treated with RT across two tertiary cancer centres.
- Investigators used 9,432 on-treatment CBCT scans together with routine weekly weight measurements to characterize body-composition changes during RT.
- Skeletal muscle was automatically measured at the C3 vertebral level across five axial slices. The analysis comprised 8,250 measurements in 246 patients from one centre and 1,182 measurements in 91 patients from the second centre.
- Both body weight and muscle area generally declined during treatment, but the two measures captured partially different biological information; their correlation was only modest.
- Faster skeletal muscle loss was independently associated with greater all-cause mortality after adjustment for established clinical prognostic factors (HR 2.50, 95% CI 1.03–6.02; p=0.03).
- In the aggregate cohort, adding weight loss or a muscle–weight interaction did not significantly improve the survival model (p=0.07). This means patients may lose clinically relevant muscle even when change on the scale appears less striking.
- In the definitive chemoradiotherapy subgroup, after accounting for feeding-tube use, muscle loss, weight loss, and their interaction all provided independent prognostic information, with the interaction significantly improving model fit (p=0.01).
- Because this was observational, the findings do not establish that interventions preventing muscle loss will improve survival; residual confounding from disease biology, nutrition, systemic therapy, and baseline physiological reserve remains possible.
CLINICAL TAKEAWAY
Routine CBCT may contain clinically useful information beyond anatomy and setup: longitudinal muscle change could identify patients deteriorating during head and neck RT before weight alone makes that risk obvious. Whether automated detection followed by nutritional or exercise intervention improves outcomes now needs prospective testing.