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.