Pathologically determined tumor volume vs pathologic T stage in the prediction of outcome after surgical treatment of oropharyngeal squamous cell carcinoma

IMPORTANCE: Traditional prognostic models for squamous cell carcinoma of the head and neck are based on the TNM staging system. However, there is growing evidence that tumor volume (TV) may be a more accurate predictor of outcome. OBJECTIVE: To determine whether pathologic TV (pTV) in patients with oropharyngeal squamous cell carcinoma treated surgically is a more significant predictor of outcome compared with pathologic tumor (pT) stage. DESIGN, SETTING, AND PARTICIPANTS: Review of patients whose treatment was managed between January 1, 1985, and December 2005 at a US tertiary referral cancer center. The participants included 159 patients who had undergone primary surgery for oropharyngeal squamous cell carcinoma and had 3 dimensions reported on histopathologic testing. MAIN OUTCOMES AND MEASURES: The pTV was calculated as the product of the 3 dimensions expressed in cubic centimeters. For comparison of pT stage with pTV in outcome prediction, concordance indexes were generated using the bootstrap method (n = 1000) to quantify the predictive accuracy of recurrence and survival outcomes. Concordance indexes were then compared and a significant difference was considered when P < .05. RESULTS: The median age of the patients was 59 years (range, 22-84 years) and 106 were male (67%). Sites of the tumors were base of the tongue (86 patients [54%]), tonsil (48 [30%]), soft palate (24 [15%]), and posterior pharyngeal wall (1 [1%]). The median follow-up time was 64 months (range, 1-272 months). The median tumor volume was 6.8 cm³ (range, 0.1-162.5 cm³). Pathologic TV was a significant predictor of disease-specific mortality. Unlike pT stage, pTV was a significant predictor of local recurrence, regional recurrence, and distant recurrence. Comparison of concordance indexes showed that pTV was a significantly better predictor of disease-specific mortality, local recurrence, and distant recurrence (all P < .05). CONCLUSIONS AND RELEVANCE: Pathologic TV outperforms pT stage in the prediction of outcome following surgical treatment of oropharyngeal cancer. Tumor volume should be considered in the design of prospective surgical trials.