Pleural metastases from differentiated thyroid cancer: clinical features and long-term outcomes

Pleural metastasis (PM) is rare in patients with differentiated thyroid cancer (DTC). Radioiodine (131I) therapy has been the main treatment for postoperative metastasis and recurrence of DTC. However, clinical data on PM from DTC are limited. This study investigated the clinicopathological characteristics of patients with PM from DTC that were treated surgically and with 131I therapy and evaluated their long-term prognosis and prognostic factors.

A review of the Shanghai Sixth People's Hospital medical records from 2010 to 2023 identified PM in 27 of 14,473 patients with DTC. Overall survival (OS) was assessed by the Kaplan-Meier method.

The prevalence of PM in DTC was 1.87‰ (27/14,473). The median age at the time of initial diagnosis of PM was 59 years (range: 34-79). At the end of follow-up, eight patients (29.63%) had disease progression (PD), four (14.81%) had a partial response, and the remainder had stable disease; no patient achieved complete response. Twelve patients (44.44%) died, and 15 (55.56%) survived. Thirteen patients (48.15%) did not show 131I avidity, and 16 (59.26%) had radioiodine-refractory DTC (RR-DTC). Twenty patients (74.07%) had malignant pleural effusion (MPE), which was large in 11 cases (40.74%) and moderate in two. More-than-moderate MPE (P = 0.031), lack of 131I avidity (P = 0.041) and RR-DTC (P = 0.030) were significantly associated with worse 5-year OS in patients with PM of DTC.

PM is rare in DTC. Lack of 131I avidity, RR-DTC and more-than-moderate MPE are associated with poor OS in patients with DTC and PM.