Abstract
Because of the low mortality rate of well-differentiated thyroid cancer (WDTC), investigation of the clinical course leading to death is limited. We analyzed the cause of death and clinical course from diagnosis to death in patients who died of WDTC. A total of 592 WDTC patients died between 1996 and 2018. After exclusion, 79 patients were enrolled and divided into four groups based on their clinical course; that is, inoperable at the time of diagnosis (inoperable), distant metastasis (DM) detected at the time of diagnosis (initial-DM), DM detected during follow-up (late-DM), and loco-regional disease (L-R). Lung (55.6%) in papillary thyroid carcinoma (PTC) and bone (46.7%) in follicular thyroid carcinoma (FTC) were the most common metastasis locations. The most common causes of death were respiratory failure (32.3%) and airway obstruction (30.6%) in PTC, and complications due to immobilization arising from bone metastasis (35.3%) in FTC. Brain metastasis was found in 13.3% of patients and had the worst prognosis. The overall survival (OS) differed significantly (p = 0.001) according to clinical course; the inoperable had the shortest survival, followed by the initial-DM, L-R, and late-DM. However, OS did not differ significantly between PTC and FTC patients with initial-DM (p = 0.83). Other causes of death were far more common than death resulting from WDTC. In patients dying of WDTC, the major cause of death varied by metastatic site. OS differed according to clinical course, but not histologic type. Timing and DM sites differed between PTC and FTC.
Highlights
Papillary thyroid carcinoma (PTC) and follicular thyroid carcinoma (FTC) are referred to as well-differentiated thyroid carcinoma (WDTC), which arises from thyroid follicular cells [1]
Categorical variables are shown as number and continuous variables are shown as median. n, number of patients; Not assessed, lymph nodes were not assessed during surgery; LN, lymph node; Total, total thyroidectomy; External beam radiation therapy (EBRT), external beam radiation therapy; RAI, radioactive iodine. †Primary tumor size in inoperable group was measured by thyroid ultrasound
We focused on the cause of death and overall clinical course in 79 patients who died of WDTC, and separated them into papillary thyroid carcinoma (PTC) and FTC groups
Summary
Papillary thyroid carcinoma (PTC) and follicular thyroid carcinoma (FTC) are referred to as well-differentiated thyroid carcinoma (WDTC), which arises from thyroid follicular cells [1]. PTC and FTC comprise approximately 85% and 11% of all thyroid cancer cases, respectively [2]. It is difficult to investigate the clinical course from diagnosis to death in patients who die of WDTC because of its indolent clinical course and low mortality rate. Loco-regional lymph node metastasis is common in PTC, whereas from that of PTC [14]. Loco-regional lymph node metastasis is common in PTC, whereas distant distant metastasis is more common metastasis is more common in FTC. We investigated the clinical course from diagnosis to death and the and FTC separately. We investigated the clinical course from diagnosis to death and the cause of of death death in in patients patients who who died died of of WDTC.
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