728P - Brain metastases in advanced thyroid carcinoma: Clinical and molecular characteristics and outcomes

Background

Brain metastases (BrM) from thyroid cancer are considered rare. Staging brain MRI is not routinely recommended by guidelines. Prognostication, management, and outcomes remain understudied in this population.

Methods

This is a single-center retrospective study of advanced (unresectable or metastatic) thyroid cancer treated at the Princess Margaret Cancer Centre from 2000 to 2020 who developed BrM. All patients (pts) had tumour next generation sequencing (NGS) by targeted gene panel. Clinical, molecular characteristics and treatment modalities were reviewed. Overall Survival (OS) was estimated from the date of BrM diagnosis using the Kaplan-Meier method.

Results

Of 166 consecutive pts with advanced thyroid cancer who had NGS, 36 pts had documented BrM (21,7%). Median age was 52,8yo. Most BrM pts (80,6%) were of follicular cell origin (papillary TCs beig the most frequent) and the remaining (19,4%) was of C-cell origin (Medullary TC) Most pts (72%) were asymptomatic and diagnosed with BrM incidentally from staging head/neck CT scan (16/26) or brain MRI/CT (9/26). 42% of pts were on systemic treatment before BrM diagnosis. The most frequent molecular alterations were: BRAFV600E (n=16), NRAS (n=8), TERT promoter (n=8), and RET (n=7). Median OS (mOS) from BrM to death was 20,1 months (m) (95% CI 1,87-39,1). Treatment for BrM included surgery (14%) and radiation (89%). Histological subtypes were not significantly associated with OS. Pts harboring BRAF or NRAS mutations had mOS of 38.4 m, while RET and other alterations had mOS of 18.5 m and 1.2m, respectively (p=0.01). Pts with 1-3 BrM had better OS than those with ≥ 4 BrM (p = 0,025); Pts who underwent BrM resection had a trend to improved OS compared to radiation alone (61.2 vs 18.1 m, p=0.38).

Conclusions

This study is the one of the largest analyses of BrM from advanced thyroid cancer with detailed clinical and genomic characterization including all histology subtypes. We found a higher incidence of BrM than previously reported. Most were diagnosed with BrM incidentally. Number of BrM (1-3), BrM treatment modality and Molecular subtype may be prognostic. Staging brain MRI may facilitate earlier BrM detection. Further studies are needed to confirm the impact of earlier BrM diagnosis on pts outcomes.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Princess Margaret Cancer Centre.

Funding

Princess Margaret Cancer Centre.

Disclosure

All authors have declared no conflicts of interest.