Five-year relative survival and determinants of excess mortality in patients with head and neck and thyroid cancers: A population-based study from Golestan province, Northern Iran.

[BACKGROUND] We aimed to assess relative survival (RS) and determinants of excess mortality rate in patients with head and neck squamous cell carcinomas (HNSCC) and thyroid cancer in Golestan province, Northern Iran.

[METHODS] We recruited new primary HNSCC and thyroid cancer cases from Golestan, 2006-2016. Five-year age-standardized RS with their 95% confidence intervals (CIs) were calculated. The relationships between different variables with excess mortality rates were assessed by estimating adjusted excess hazard ratios (aEHRs) with their 95% CIs.

[RESULTS] Overall, 718 cases of HNSCC and 386 thyroid cancer cases were enrolled. Five-year age-standardized RS (95% CI) were 36% (31-41) and 61% (52-69) in HNSCC and thyroid cancer patients, respectively. There were significant relationship between excess mortality rates in HNSCC patients with metastasis (aEHR= 3.31; 95%CI: 2.26-4.84), treatment type (4.19; 2.54-6.91, for no treatment as compared to receiving both surgery and chemoradiotherapy), age (2.16; 1.57-2.96, for older age group) and smoking (2.00; 1.45-2.75, for smokers as compared to non-smokers). Determinant of the excess mortality in thyroid cancer patients included metastasis (19.65; 8.08-47.79), tumor morphology (12.27; 4.62-32.58, for anaplastic cancer as compared to papillary cancer), treatment type (8.95, 4.13-19.4, for no treatment as compared to receiving both surgery and iodine therapy) and age (2.31; 1.17-4.54, for older age group).

[CONCLUSION] Our findings suggested low RS for thyroid cancer in our population, while the estimates for HNSCC were comparable with other population. Metastasis, treatment type and age were determinants of mortality both in thyroid and HNSCC patients.