428. PHARYNGEAL SQUAMOUS CELL CARCINOMA AND RISK OF LATER ESOPHAGEAL SQUAMOUS CELL CARCINOMA.

Introduction Pharyngeal squamous cell carcinoma is a known risk factor for later squamous cell carcinoma of the esophagus. We investigated whether the risk of esophageal carcinoma is high enough to justify routine gastroscopy surveillance in a northern European population. If the risk among patients with pharyngeal carcinoma corresponds to the risk among patients with Barretts esophagus of developing adenocarcinoma, it could justify surveillance. Method Histopathology data from pharyngeal and esophageal biopsies obtained 1980–2016 in Sweden's 28 pathology departments were linked to national population-based healthcare registers. We calculated a subdistribution hazard ratio (HR) comparing the risk of esophageal cancer and death in patients with pharyngeal carcinoma to a matched general population. Result In total 1399 patients with pharyngeal cancer were identified. 344 were excluded due to age under 18 years, previous esophageal cancer, death or cancer within 6 months of diagnosis. Thus, 1055 patients remained. Median follow up time was 5,1 years. 78% were men and median age at diagnosis of pharyngeal cancer was 64 years. Four (0.38%) patients developed esophageal squamous cell carcinoma during follow-up, equal to 1 in 263 patients (HR = 14,32; 95%CI = 1,55-132,30). 855 of the patients (81%) died during follow-up (HR = 7,65; 95% = 6,82-8,59). Discussion The yearly risk of developing esophageal squamous cell carcinoma was 0,07%, which is lower than the risk among patients with Barretts esophagus. Therefore, we find no support for long-term endoscopic surveillance among patients with pharyngeal cancer. [ABSTRACT FROM AUTHOR]