Endocrine Abstracts

Introduction: The BRAF ^V600E mutation has been reported in 27– 90% of Papillary Thyroid Carcinoma (PTC). BRAF ^V600E may be associated with adverse outcomes in PTC. It is unknown if detection of BRAF ^V600E can play a key role in prognosis, and can be used as a surrogate-marker of poor outcomes in PTC.

Objectives: • To investigate prevalence of BRAF ^V600E mutation in TC using digital droplet PCR (ddPCR).

• To use Whole Exome Sequencing (WES) of tumour DNA to validate ddPCR methodology.

• To determine whether BRAF ^V600E is associated with adverse outcomes in TC.

Methods: Patients were recruited from University Hospitals of Leicester NHS Trust thyroid cancer service (March 2022 – April 2023). Formalin-fixed, Paraffin-Embedded (FFPE) tissue blocks were obtained from archival stores. DNA was isolated using the Qiagen GeneRead Kit and quantified using Qubit 2.0 HS Kit. BRAF ^V600E was detected using Bio-Rad assay on QX200 ddPCR system. WES was performed at Novogene Lab (UK). Follow-up was for 12 months at intervals in line with routine clinical reviews. Adverse outcomes were recorded using clinical and radiological findings.

Results: Twenty-three patients (14 males and 9 females) had accessible tumour FFPE blocks. Mean age was 54 years (range 26 – 84) across four subtypes: (PTC n = 12), follicular (FTC n = 5), medullary (MTC n = 3), anaplastic (ATC n = 3). BRAF ^V600E was detected in 5/12 (41.6%) PTC and 1/3 (33.3%) ATC. 8/17 of the BRAF ^V600E -negative and 0/6 BRAF ^V600E -positive patients developed recurrence and/or metastases. WES results confirmed the presence of BRAF ^V600E in 5/12 (41.6%) PTC and 1/3 (33.3%) ATC.

Discussion: Both ddPCR and WES were concordant for BRAF ^V600E presence, with prevalence figures consistent with previous data. During 12-month follow-up, BRAF ^V600E did not appear to drive adverse outcomes in TC. It is therefore likely that other mutations were driving disease progression in the BRAF ^V600E -negative cohort. We plan to investigate what those driver mutations are.