Validation of the pathological classification of lymph node metastasis for head and neck tumors (HNSCC) according to the 8th edition of the TNM Classification of Malignant Tumors (8th TNM).

Abstract

6014 Background: Changes in 8th TNM edition are a specific staging for p16+oropharyngeal carcinoma and the inclusion of extracapsular spread (ECS) in N extension. We evaluate the improvement in prognostic capacity from the inclusion of the ECS in HNSCC patients treated with a neck dissection (ND). Methods: Retrospective study based on prospectively collected information of 1188 HNSCC patients (oral cavity, HPV-oropharynx, hypopharynx, or larynx) diagnosed from 1990 to 2013, treated with unilateral or bilateral ND and a minimum fw-up of 2 years. We performed 1820 ND: 410 radical, 1410 selective ND; 683 patients (60.1%) had bilateral ND. Mean lymph nodes/patient: 32.6 (SD 19.9, 7-118). In 157 cases (13.8%) ND was performed after radiotherapy (RT, n =71) or chemoradiotherapy (CHRT, n = 86) with a median interval of 8.5 weeks (6-10). 596 patients (52.4%) had postoperative RT (n=525) or CHRT (n=71). Mean fw-up: 5.6 years (SD 4.9): 213 patients (18.7%) had local failure, 158 (13.9%) regional failure, 172 (15.14%) metastases. Results: 570 patients (50.1%) had lymph node metastases, 288 (50.5%) with ECS. The 8th TNM produced upstaging of 20.9% of pN1 patients to pN2a (n=33), and of 58.4% of the patients classified as pN2 to pN3b (n=220). The 7th TNM Classification (7thTNM), 5-year cause-specific survival for pN2 (35.5%) was similar to pN3 (21.6%). In the 8th TNM, 5-year cause-specific survival for pN2 (53.3%) sits in an more intermediate position between pN1 (70.5%) and pN3 (24.0%). Five-year cause-specific survival for pN2 patients with ECS (n=217) was 22.4%, and for patients without ECS (n=157) was 51.4%. There were statistically significant differences in survival between the two reclassified groups (P=0.0001). pN1 patients in the 7thTNM did not show survival differences when stratified by the presence of ECS: 5-y SV: 63.5% for ECS (n=33), 70.5% for non-ECS (n=125) (p=0.838). Conclusions: Inclusion of ECS in the pathological classification of the 8th TNM Classification edition improved the prognostic capacity, as compared with the previous version, basically produced by the migration of 58.4% of pN2 in the 7th TNM to the new pN3b category