Metabolic tumor volume of primary tumor predicts survival better than T classification in the larynx preservation approach

We aimed to determine whether pretreatment metabolic tumor volume of the primary tumor (T‐MTV) or T classification would be a better predictor of laryngectomy‐free survival (LFS) and overall survival (OS) after chemoradiotherapy in patients with locally advanced laryngeal or hypopharyngeal cancer requiring total laryngectomy. We analyzed 85 patients using a Cox proportional hazards model and evaluated its usefulness by Akaike's information criterion. A T‐MTV cut‐off value was determined by time‐dependent receiver operating characteristic curve analysis. Interobserver reliability for measuring T‐MTV was estimated by the intraclass correlation coefficient (ICC). After adjustment for covariables, T‐MTV, irrespective of whether a continuous or dichotomized variable, and T classification remained independent predictors of LFS and OS. Large T‐MTV (>28.7 mL) was associated with inferior LFS (hazard ratio [HR], 4.16; 95% confidence interval [CI], 1.97–8.70; P = 0.0003) and inferior OS (HR, 3.18; 95% CI, 1.47–6.69; P = 0.004) compared with small T‐MTV (≤28.7 mL). The T‐MTV model outperformed the T classification model in predicting LFS and OS (P = 0.007 and 0.01, respectively). Three‐year LFS and OS rates for patients with small versus large T‐MTV were 68% vs 9% (P < 0.0001) and 77% vs 25% (P < 0.0001), respectively, whereas those for patients with T2‐T3 versus T4a were 61% vs 31% (P = 0.003) and 71% vs 48% (P = 0.10), respectively. ICC was 0.99 (95% CI, 0.99–1.00). Given the excellent interobserver reliability, T‐MTV is better than T classification to identify patients who would benefit from the larynx preservation approach.