Incidence and time trends of herpes zoster among patients with head and neck cancer who did and did not undergo radiotherapy: A population-based cohort study

PURPOSE: This study aimed to determine the risk and time trends of herpes zoster among patients with head and neck cancer, with or without radiotherapy. METHODS: A total of 2160 patients with head and neck cancer were enrolled. The radiotherapy and non- radiotherapy cohorts were frequency-matched at a 1:1 ratio according to sex, age, and index date. Moreover, 1080 matched non-cancer individuals were considered normal controls. Data were obtained from the National Health Insurance Research Database and Cancer Registry. The primary end point was the incidence of herpes zoster, and the adjusted confounding factors were age, sex, comorbidities, oncological surgery, and chemotherapy. RESULTS: The incidence of herpes zoster was higher in cancer patients than in non-cancer individuals but did not significantly differ (13.67 vs. 8.06 per 1,000 person-years, p = 0.18). The risk of herpes zoster was significantly higher in the radiotherapy cohort than in the non-radiotherapy cohort (18.55 vs. 9.06 per 1,000 person-years, p = 0.03). The 5-year incidence rates in the radiotherapy and non-radiotherapy cohorts were 8.9% and 5%, respectively (p < 0.0001). Survival analysis indicated there was no immortal time bias. The time trends in the radiotherapy cohort persistently showed a high risk within the first 2 years, which decreased thereafter. Only patients with comorbid rheumatoid arthritis showed a significantly high risk of herpes zoster (p = 0.02). Oncological surgery and chemotherapy had no impact on the development of herpes zoster. CONCLUSIONS: This nationwide population-based study showed that patients with head and neck cancer receiving radiotherapy are at an increased risk of herpes zoster. Health care professionals should pay more attention to this vulnerable group to improve their quality of life.