Koos Boeve

45 8th TNM classification prognostic value in oral cancer DISCUSSION The aim of this study was to determine the clinical impact of the addition of tumour infiltration depth and ENE in the 8 th edition of the pathological TNM classification on survival and potential alterations in treatment strategy for pT1-T2 OSCC patients who had been treated on the basis of the 7 th edition. In this study, 36% and 16% of all of the patients were restaged with the 8 th edition criteria according to the pT and pN classifications, respectively. Patients restaged as pT3 showed significantly shorter DSS than the 8 th edition pT1-T2 staged patients. Another seven (3%) patients who were restaged as pT3 could possibly have benefited from postoperative radiotherapy. This study used a well-defined 7 th edition pT1-T2 cohort with extensive clinical data to add to the current evidence validating the 8 th edition TNM classification [2,4,5]. Patients with a watchful waiting strategy of the neck were also included, which was not the case in the large ICOR study and the validation study by Matos et al. [3,4]. Recently, two other studies investigated the differences between the 7 th edition and 8 th edition TNM staging by using early-stage OSCC patients [9,10]. These studies differed from the current study by using sentinel lymph node biopsy (SLNB)-staged patients or by analysing only the pT categories and not the pN categories. This study confirms the previously mentioned validation study findings regarding the shorter survival rate of patients restaged as pT3 and pN3 with the 8 th edition criteria [2,4,5]. However, the number of restaged patients differs between studies. In this study 44% of the 7 th edition pT1 patients were restaged, versus 44% and 61% in other studies [3,4] and 24% of the pT2 patients were restaged, versus 62% and 47% in other studies [3,4]. Remarkably, one of the other studies did not restage any of the 7 th edition pT1 patients to pT3 [3]. Differences in restaging rates might be explained by differences in clinical care between the countries. In The Netherlands, people visit their general dental practitioner once a year or more, whereas one of the validation studies stated in the discussion that the restaging rates could have been limited by a high rate of advanced disease which is a reality in emerging countries [4]. Restaging to a higher classification level with the 8 th edition criteria is only possible for 7 th edition pT1-T2 patients. Consequently, the 8 th edition is clinically most relevant for these patients. This is why we used a cohort of 7 th edition pT1-T2 patients to obtain an unadulterated view of the differences in prognosis. The inclusion of only pT1-T2 patients resulted in a relatively small number of 8 th edition pT3 patients as compared with other studies. Also, the ENE rate in this study is lower than in the other 8 th edition TNM validation studies: 39% versus 51% and 53% respectively [4,5]. The inclusion of only pT1-T2 patients could explain the lower ENE rate than in studies that also included more advanced disease.