Causes of death among patients with metastatic differentiated thyroid cancer

Notwithstanding the generally positive outlook for differentiated thyroid cancer (DTC), metastatic differentiated thyroid cancer (mDTC) remains a lethal disease. In light of the current insufficient information regarding mortality causes in mDTC, our research endeavored to elucidate the factors contributing to death in patients diagnosed with mDTC.

A cohort of 187,747 differentiated thyroid cancer (DTC) cases was extracted from the Surveillance, Epidemiology, and End Results-17 cancer registry database (2000-2020) and identified 4749 patients diagnosed with mDTC. The study estimated the cumulative mortality associated with thyroid cancer, subsequent cancers, and non-cancer-related causes. Standardized mortality ratios (SMR) were employed to evaluate the disparities between observed and expected mortality rates in mDTC patients.

In the DTC cohort, with a median follow-up of 70 months, 17,582 patients (9.4%) succumbed during the follow-up period. In the mDTC cohort, 2046 deaths (43.1%) occurred, with the 5-year cumulative mortality being highest for brain and liver metastases at 53.1% and 49.0%, respectively. During follow-up, 7.1% of patients with mDTC expired from subsequent cancers, with the largest proportion attributed to lung cancer. During the mDTC period, the most prevalent cause of non-cancer mortality was cerebrovascular diseases (SMR, 1.45; 95% CI, 1.05-1.94).

Non-cancer-related mortality constitutes a substantial proportion of mDTC and exhibits an increasing trend. Enhanced attention should be directed toward the management of mDTC survivors, with individualized treatment and follow-up plans tailored to patient-specific factors, while providing comprehensive guidance regarding potential future health risks.