Clinical and molecular features and survival in thyroid cancer with brain metastases.

Abstract

2023 Background: Brain metastases (BM) in advanced thyroid cancer are rare; however, they may be underreported as staging brain imaging is not routine. Prognostic features and molecular alterations for this group are poorly described. We characterized the clinical and molecular features of thyroid cancer with BM and evaluated differences in survival. Methods: In this single-center retrospective analysis, patients with metastatic radioactive iodine refractory well-differentiated, poorly-differentiated, or medullary thyroid carcinoma seen at the Princess Margaret Cancer Center from 2007-2022 were included. Electronic medical records were reviewed to collect clinicopathologic and treatment data. All patients had tumor next-generation sequencing (NGS) by a targeted gene panel. Overall survival (OS) from initial medical oncology consultation was analyzed using the Kaplan-Meier method and univariate and multivariate Cox proportional hazards models. Results: Of 248 patients with advanced thyroid cancer, 41(17%) were diagnosed with BM. The median interval from thyroid cancer diagnosis to BM development was 6.49 years (y) (IQR 3.51- 14.35 y). The median age at the time of BM diagnosis was 63.6 y and 23 (56%) were male. Most (76%) were asymptomatic at the diagnosis of BM and 80% had an ECOG of 0-1. Among patients with well-differentiated histology, 27 (18%) developed BM, while 7 (12%) with poorly-differentiated and 7 (19%) with medullary thyroid cancer developed BM. The most common molecular alterations included BRAFV600E (n=19), TERT (n=11), RAS (n=9), RET (n=8), and FANCA (n=3). Patients were treated with surgery (n=5), stereotactic radiation (n=21), whole brain radiation therapy (n=12), or a combination of both (n=2). OS was similar in patients with BM compared to those without (6.05 vs 6.45 y). There were no differences in histology or molecular alterations between patients that developed BM compared to those who did not. The median survival from the time of BM was 3.23 y. Patients with BM with ≥4 lesions had worse survival (0.52 vs 5.09 y, p=0.01). There were no differences in survival based on histology, symptoms, treatment or molecular alterations among those with BM. Conclusions: This is one of the largest reported thyroid BM cohorts and the first with complete NGS. The prevalence of BM in our cohort was higher than previously described, often diagnosed incidentally. Screening for BM in advanced thyroid cancer may detect higher rates, offering prognostic insights. While the number of BM was predictive of survival, molecular alterations did not predict BM development or survival and larger studies are needed.