Prognostic effects of surgery or radiotherapy on adenoid cystic carcinoma of the head and neck: a retrospective cohort study

Background: There is little evidence exploring prognostic effects of surgery and radiotherapy on adenoid cystic carcinoma (ACC) of the head and neck. This study sought to evaluate the prognostic effects of surgery or radiotherapy on ACC of the salivary gland, oropharynx, and nose, nasal cavity, and middle ear. Methods: In this cohort study, the data of 2,392 participants with ACC of the head and neck were extracted from the Surveillance, Epidemiology and End Results (SEER) database. Participants were divided into the salivary gland group (n=1,351), the mouth and oropharynx group (n=563), and the nose, nasal cavity, and middle ear group (n=478). Baseline characteristics were assessed via questionnaires or laboratory analysis and outcome variables were all-cause death and cancer-specific death of patients. Baseline data were collected in 2004, and patients were followed-up to 2016. The survival time of patients were recorded. Univariate and multivariate Cox regression analyses explored the effects of surgery and radiotherapy on overall prognosis of ACC patients. Fine-Gray test assessed the effects of surgery and radiotherapy on cancer-specific mortality of ACC patients. Results: In total, 766 died and 1,626 survived with a median survival time of 9.92 years. After adjusting for confounders, patients with ACC of the salivary gland who underwent surgery had a decreased risk of all-cause mortality [hazard ratio (HR) =0.51; 95% confidence interval (CI): 0.36-0.71] and cancer-specific mortality (HR =0.57; 95% CI: 0.34-0.97). Surgery was found to be a protective factor for the risk of all-cause mortality (HR =0.47; 95% CI: 0.28-0.78) and cancer-specific mortality (HR =0.70; 95% CI: 0.33-1.50) of patients with ACC of the mouth and oropharynx after adjusting for confounders. After adjusting for confounders, patients with ACC of the nose, nasal cavity, and middle ear who underwent surgery had a decreased risk of all-cause mortality (HR =0.46; 95% CI: 0.30-0.70) and cancer-specific mortality (HR =0.35; 95% CI: 0.20-0.61). Conclusions: Surgery was associated with a decreased risk of mortality in patients with ACC of the salivary gland, oropharynx, and nose, nasal cavity, and middle ear, which suggested the value of surgery for improving their prognosis.