ORIGINAL ARTICLE Comparison of tumor volume, thickness, and T classification as predictors of outcomes in surgically treated squamous cell carcinoma of the oral tongue Manish Mair MS 1 | Deepa Nair MS 1 | Sudhir Nair MS 1 | Akshat Malik MS 1 | Aseem Mishra MS 1 | Sadhana Kannan Msc 1 | Saurabh Bobdey MD 2 | Hitesh Singhvi MDS 1 | Pankaj Chaturvedi MS 1 1 Department of Head and Neck Oncosurgery, Tata Memorial Hospital, Mumbai, India 2 Department of Medical Records, Biostatistics and Epidemiology, Tata Memorial Hospital, Mumbai, India Correspondence Pankaj Chaturvedi, Department of Head and Neck Oncosurgery, 12th Floor, Homi Bhabha Block, Tata Memorial Hospital, E. Borges Road, Parel, Mumbai 400012, India., Email address: chaturvedi. pankaj@gmail.com Abstract Background: As per TNM classification, superficial tumors with a favorable prog- nosis are fallaciously clubbed together with unfavorable, deeply infiltrating lesions in the same classification. Methods: This is a retrospective study of 588 patients with treatment-naive oral tongue cancers. Binary logistic regression was used to identify predictors of nodal metastasis and extracapsular spread (ECS) using tumor volume and thickness as sepa- rate models. The C-index was generated to quantify predictive accuracy of T classification, thickness, and tumor volume for survival. Results: Compared to T classification, tumor volume and thickness were better pre- dictors of nodal metastasis and ECS. Predictive accuracy for disease-free survival (DFS) and overall survival (OS) given by C-index was equal and better for thickness (0.60 and 0.69) and tumor volume (0.61 and 0.69) as compared to T classification (0.59 and 0.64, respectively). For early-stage T1 to T2 oral tongue cancer, thickness is a better predictor of nodal metastasis as compared to tumor volume and T classification. Conclusion: Concordance between the tumor thickness and volume proves that tumor thickness can be taken as a surrogate and reliable predictor of outcomes instead of calculating the tumor volume. KEYWORDS nodal metastasis, survival, T classification, thickness, tumor volume 1 | INTRODUCTION Nodal metastasis in patients with oral cancer is strongly related to poor survival. 1 Furthermore, pathological evidence of regional nodal metastases with extracapsular spread (ECS) has been associated with a significant decrease in survival and increased rates of regional recurrence and distant metastases. 2–4 Tumor (T) classification is an important pre- dictor of nodal metastasis and prognosis. 5,6 However, T classification as defined by the American Joint Committee on Cancer (AJCC) fails to represent the true 3D volume of the primary tumors. As a result, superficial tumors with a favorable prognosis are fallaciously clubbed together with unfavorable, deeply infiltrating lesions in the same stage. Huang et al 7 showed that tumor thickness of >4 mm is a strong predictor of nodal metastasis in tongue cancers. Vari- ous studies have also shown that tumor volume in head and neck cancers assessed by imaging may give a better Head & Neck. 2018;1–9. wileyonlinelibrary.com/journal/hed V C 2018 Wiley Periodicals, Inc. | 1 Received: 19 December 2016 | Revised: 13 September 2017 | Accepted: 5 February 2018 DOI: 10.1002/hed.25161