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 5 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 patients with DTC were identified between 2012 and 2017 from all Swedish hospitals treating patients with DTC. 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 1, 3, and 5 years. Summary measures for physical and mental QOL 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 5 years following DTC treatment, physical QOL did not change significantly with time, while mental QOL improved by on average 0.61 (p < 0.001) per year. TSH levels were not predictive of either physical or mental QOL, or their change over time. At 5 years, there was a significant difference in physical and mental QOL compared with 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 5 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 patients with DTC is not explained by TSH suppression. Although overall differences in physical and mental HRQOL compared with the general population were small 5 years after treatment, several specific psychosocial HRQOL domains were clinically meaningfully reduced. Psychosocial health issues should be screened for during DTC follow-up.
Keywords: nationwide; prospective study; quality of life; thyroid cancer; thyroid-stimulating hormone.