Five-Year Follow-Up of Health-Related Quality of Life in Differentiated Thyroid Cancer Patients Treated with Total Thyroidectomy and Radioiodine in Sweden: A Nationwide Prospective Cohort Study

Background Despite a good prognosis, survivors of differentiated thyroid cancer (DTC) may have reduced health-related quality of life (HRQOL) many years after treatment, and it is unclear how suppression of thyroid stimulating hormone (TSH) may contribute to HRQOL. This study investigated changes in HRQOL in the five years following DTC treatment, the association between HRQOL and TSH suppression, and how HRQOL compares to the general population. Methods In this nationwide prospective cohort study, 487 DTC patients were identified between 2012 and 2017 from all Swedish hospitals treating DTC patients. Patients treated with total thyroidectomy and planned for radioiodine answered the Swedish version of the Short Form-36 Health Survey (SF-36) and a study specific questionnaire at treatment and after one, three and five years. Summary measures for physical and mental quality of life were derived from the SF-36, and TSH values were collected from patient records. To study changes in HRQOL over time, linear mixed models were fitted on multiply imputed data, with all patients and measurement points included in the model. Results In total, 351 patients consented to participate in the study. In the five years following DTC treatment, physical quality of life did not change significantly with time, while mental quality of life improved by on average 0.61 (p<0.001) per year. TSH levels were not predictive of either physical or mental quality of life, or their change over time. At five years, there was a significant difference in physical and mental quality of life compared to the Swedish general population, but effect sizes were small (Cohen's d=0.29 and -0.21, respectively). The SF-36 domains general health, vitality, social functioning and mental health were lower at five years compared with the general population (difference 8.7-13.3), and these differences were clinically significant. Conclusions The mental component of HRQOL improves over time following DTC treatment. HRQOL in DTC patients is not explained by TSH suppression. Though overall differences in physical and mental HRQOL compared to the general population were small five years after treatment, several specific psychosocial HRQOL domains were clinically meaningfully reduced. Psychosocial health issues should be screened for during DTC follow-up.