Low Skeletal Muscle Mass as a Key Predictor of Postoperative Diet Outcomes in Circumferential Hypopharyngeal Cancer Reconstruction.

Abstract

Objective: To evaluate the association between preoperative lumbar skeletal muscle index (LSMI) and postoperative dietary outcomes (regular diet versus texture-modified diet) in patients undergoing circumferential hypopharyngeal cancer resection with tubed anterolateral thigh flap reconstruction.

Methods: This single-center retrospective cohort study included 73 patients between 2009 and 2020. LSMI was calculated from lumbar skeletal muscle cross-sectional area at the C3 vertebral level on preoperative CT scans. The primary outcome was dietary restriction, defined as Functional Oral Intake Scale ≤ 6 at ≥ 12 months postoperatively. Candidate predictors (pre-, intra- and postoperative) with p < 0.20 in univariate screening underwent theory-driven confounder assessment based on directed acyclic graphs, prior literature, and clinical knowledge. Change-in-estimate criterion (Δβ ≥ 10%) supported selecting confounding. LSMI components (C3CSA, L3CSA, age, sex, weight, height, BMI) were excluded from adjustment to prevent overadjustment for mediators and multicollinearity. The final model analyzed LSMI as a continuous predictor with logistic regression.

Results: Fifteen patients (20.5%) developed dietary restriction (FOIS < 7). Three confounders (Eichner A, Stage IV, hemoglobin) for LSMI were identified. Multivariable adjustment improved model fit (AIC: 65.8 → 63.4; Nagelkerke R ²: 0.237 → 0.383) while maintaining statistical significance. Each 1 cm²/m² increase in LSMI was associated with a 16.1% reduction in the odds of FOIS < 7 (adjusted OR: 0.839; p = 0.006). The optimal LSMI cut-off value was 42.82 cm²/m².

Conclusion: Preoperative LSMI independently predicts long-term dietary outcomes after hypopharyngeal reconstruction. Restricting the cohort to uniform resection and reconstruction methods clarified the relationship between skeletal muscle mass and swallowing function, enabling precise risk stratification and supporting targeted prehabilitation interventions.

Level of evidence: 4.