Prognostic Value Of Radiological Extranodal Extension Detected By Computed Tomography For Predicting Outcomes In Head And Neck Squamous Cell Cancer Patients Treated With Radical Chemoradiotherapy.

6560 Background: As per the AJCC 8th edition ENE/ECS is the most important predictor for N staging of HNSCC and is one of the key predictor of outcomes. Because ENE/ECS is based on pathological findings after surgery and it is difficult to predict outcomes for locally advanced squamous head and neck cancer (LASHNC) treated radically with CCRT. We hypothesized that ENE assessed by CT imaging (rENE) may directly correlate with outcomes in LASHNC treated radically with CCRT. Methods: This open-label, investigator-initiated, phase 3, randomized trial was conducted from 2012 to 2018. Adult patients with LASHNC who were fit for radical chemoradiation were randomized 1:1 to receive either radical radiotherapy (66-70 grays) with concurrent weekly cisplatin (30 mg/m 2 ) (CRT) or the same schedule of CRT with weekly nimotuzumab (200 mg) (NCRT). 536 patients were accrued,182 were excluded due to non-availability DICOM CT scan, 354 patients were analysed for rENE (based on 6 criterion for metastasis and 3 for rENE). Near equal distribution of patients was achieved in CRT arm (170 patients) and NCRT arm (184 patients). There were 181 (51.1%) oropharynx and 173(48.9%) larynx and hypopharynx patients. We evaluated association of radiological ENE and clinical outcomes.The endpoints were disease-free survival (DFS), duration of locoregional control (LRC), and overall survival (OS). Results: There were 244(68.9%) patients with radiologically metastatic nodes, out of which 140(57.3%) had rENE. There was no significant association between rENE and CRT (p value 0.3) or NCRT (p value 0.412). The median follow-up was 33.0 months (95%CI 30.7-35.2 months). Complete response was achieved in 204 (57.6%) cases, PR/SD in 126(35.6%) cases and PD in 24(6.8%) cases. rENE positive patients had poor overall 3-year survival (46.7%), poor DFS (48.8%) and LRC (39.9%) than rENE negative cases (63.6%, 87%, 60.4%). rENE positive cases had 1.71 times increase chances of incomplete response than rENE negative cases. Overall stage, clinical positive node, response, rENE and site were the only significant factors for predicting OS, DFS and LRC. Conclusions: In conclusion, pre-treatment rENE can be regarded as an independent prognostic factor for survival (OS, DFS, LRC) in patients with LASHNC treated radically with CCRT. Pre-treatment rENE is not only associated with CCRT response but is also associated with poor prognosis and hence rENE, as an imaging biomarker, can stratify responder’s vs non-responders. Clinical trial information: CTRI/2014/09/004980 .