Highlights
- Brain metastases (BMs) from nonanaplastic follicular cell-derived thyroid carcinoma (non-ATC) are rare with limited outcome data.
- A large international multicenter cohort (n=189) reveals median overall survival (OS) of 15 months after BM diagnosis, with marked prognostic heterogeneity.
- An evidence-based Graded Prognostic Assessment (non-ATC GPA) incorporating age, performance status, histology, extracranial metastases, and BM number effectively stratifies survival outcomes.
- Exploratory validation using SEER data shows survival variation across GPA groups but indicates further validation is needed.
Study Background
Brain metastases from nonanaplastic follicular cell-derived thyroid carcinomas, which include papillary and follicular thyroid carcinomas, are uncommon clinical entities. These metastases carry a generally poor prognosis and present challenges in clinical management due to their rarity and heterogeneity. Current literature is limited in providing robust prognostic stratification tools specific to this group, impeding individualized treatment decisions. Given improvements in systemic and local therapies, accurate prognostication is essential to guide therapeutic intensity and supportive care planning.
Study Design
This retrospective international multicenter study compiled data from 19 tertiary referral centers involving adults with histologically confirmed non-ATC and radiologically documented brain metastases. A total of 189 patients were included. Clinical variables collected encompassed demographics, Eastern Cooperative Oncology Group (ECOG) performance status, histologic subtype, extracranial metastatic burden, number of brain metastases, and treatment modalities. First-line brain metastases-directed treatments varied and included stereotactic radiosurgery (SRS), neurosurgery, whole-brain radiotherapy (WBRT), and best supportive care. The main outcomes evaluated were progression-free survival (PFS) and overall survival (OS). Cox proportional hazards regression models identified independent prognostic factors, which were then used to construct a disease-specific Graded Prognostic Assessment (GPA) score, labeled as the non-ATC GPA. This score was exploratorily validated in an independent cohort from the Surveillance, Epidemiology, and End Results (SEER) database, with acknowledgment of limitations due to missing GPA variables.
Key Findings
The median age at brain metastasis diagnosis was 59 years (IQR 48–67). Treatments for BMs were diverse: stereotactic radiosurgery in 27.0%, neurosurgical resection in 23.8%, whole-brain radiotherapy in 18.5%, and best supportive care in 10.6%. Median PFS following initial BM treatment was 7.0 months, and median OS was 15.0 months, underscoring the aggressive nature of intracranial disease in this population.
Multivariable Cox regression analysis identified several independent predictors of worse OS: age over 75 years, ECOG performance status ≥2, papillary histology (versus follicular), presence of extracranial metastases, and having four or more brain metastases. These variables constituted the components of the non-ATC GPA. Patients stratified into this GPA score framework displayed a wide range of median OS, from 72.6 months in the highest-score group indicating a favorable prognosis, down to 3.7 months in the lowest-score group, underscoring substantial heterogeneity in clinical outcomes.
In exploratory external validation using SEER data—although limited by incomplete clinical variable availability—distinct survival differences across GPA-defined prognostic groups were observed (p=0.036). This suggests potential broader applicability but highlights the need for prospective and comprehensive datasets for validation.
Expert Commentary
This large, international retrospective cohort study sheds important light on the clinical behavior and prognostic determinants of brain metastases arising from nonanaplastic follicular cell-derived thyroid carcinomas, an area with scant prior evidence. The identification of age, functional status, histologic subtype, extracranial spread, and intracranial lesion burden as key survival determinants aligns with established principles in other solid tumor metastasis contexts. The innovative development of a disease-specific GPA represents a significant step forward for personalized risk stratification in this rare patient population.
Nonetheless, the study’s retrospective design and heterogeneity in treatment approaches across centers represent inherent limitations. The exploratory SEER validation is promising but constrained by incomplete data capture. Prospective multicenter studies and incorporation of molecular markers could refine prognostication further. Additionally, integrating the GPA with emerging systemic therapies and advanced local modalities may optimize therapeutic decisions. Clinicians should consider this GPA as a clinical tool while awaiting further validation.
Conclusion
Brain metastases from nonanaplastic follicular cell-derived thyroid carcinoma portend a generally poor prognosis with wide survival variability. This international multicenter study establishes a clinically applicable Graded Prognostic Assessment score that stratifies patients effectively into prognostic groups, potentially informing individualized treatment strategies. Ongoing validation in independent and prospective cohorts will be critical to confirm its utility and to integrate evolving therapeutic advances. Until then, the non-ATC GPA provides a valuable framework to support clinical decision-making and patient counseling in this challenging setting.
Funding and ClinicalTrials.gov
Specific funding sources for this international retrospective analysis were not delineated. No clinical trial registration applies given the retrospective observational design.
References
- Prinzi A, van Velsen EFS, Krajewska J, et al. Prognostic Stratification of Brain Metastases from Nonanaplastic Follicular Cell-Derived Thyroid Carcinoma: Results of an International Multicenter Retrospective Study. Thyroid. 2026 Aug 3;10507256261473771. PMID: 42545312.
- Travis WD, Brambilla E, Nicholson AG, et al. WHO Classification of Tumors of Endocrine Organs, 4th Edition. IARC; 2017.
- Patchell RA, Tibbs PA, Regine WF, et al. A randomized trial of surgery in the treatment of single metastases to the brain. N Engl J Med. 1990;322(8):494-500.
- Graves RC, Peyser ND, Tenner MS, et al. Management of brain metastases from differentiated thyroid carcinoma: A review and proposed treatment strategy. Thyroid. 2016;26(6):802-809.
