Koos Boeve

37 8th TNM classification prognostic value in oral cancer INTRODUCTION In 2016, the 8 th edition of the American Joint Committee on Cancer (AJCC) TNM staging manual was released [1]. As compared with the 7 th edition, tumour infiltration depth and extranodal extension (ENE) were incorporated into the pathological TNM classification for oral squamous cell carcinoma (OSCC) [1,2]. On the basis of the 8 th edition criteria, 7 th edition pT1 patients with a tumour infiltration depth between 5 and 10 mm are restaged as pT2 and all pT1 and pT2 patients with a tumour infiltration depth of >10 mm are restaged as pT3. Following the pN classification in the 8 th edition, cases with a single positive lymph node <30 mm in diameter with ENE are restaged from pN1 to pN2b, and all other ENE- positive patients are restaged as pN3b. The incorporation of tumour infiltration depth and ENE in the pathological TNMclassification was based on data from both the International Consortium for Outcome Research in Head and Neck Cancer (ICOR) ( n = 3149) and the National Cancer Data Base (n = 7264) [2,3]. The 8 th edition has been validated in various independent databases: the pT and pN classifications by Lydiatt et al. (n = 1792) [2] and Matos et al. (n = 298) [4], and the pN classification by Garcia et al. (n = 1137) [5]. These studies confirmed a better prediction of survival per stratification with the 8 th pTNM classification edition, whereby patients who had been upstaged because of the incorporation of tumour infiltration depth and ENE generally had lower survival rates. Despite the validation with big data, the clinical impact for small tumours (pT1-2) is not really clear. As mentioned by Matos et al. and the ICOR study, their populations were limited to patients undergoing neck dissections. Patients with a clinically negative neck and not treated with selective neck dissections - also known as watchful waiting - were not included [3,4].This point is important because incorporationof infiltrationdepth in thepT classification could also influence prognosis and as a result change the treatment strategy for these early- stage patients. Therefore, our aim was to study the clinical impact of the 8 th edition pTNM classification on the survival of 7 th edition pT1-T2 patients treated with surgical resection of the tumour combined with neck dissection or a watchful waiting strategy. We selected pathologically staged T1-T2 OSCC patients from our large and homogeneous database with extensive clinicopathological and long-term follow-up data [6,7]. MATERIAL AND METHODS Patients This cohort with reassessed tumour infiltration depth has been previously described [6,7]. Briefly, 246 consecutive patients with pT1-T2 OSCC according to the 7 th edition, diagnosed