THE ROLE OF BRAF MUTATION STATUS IN SURGICAL TREATMENT OF WELL-DIFFERENTIATED THYROID CANCER

Background. Papillary thyroid carcinoma (PTC) accounts for 80 % of all well-differentiated thyroid cancers. Mutation of the BRAF gene (V600E) is one of the most common prognostic factors for PTC. Various studies showed different degree of correlation between BRAF (V600E) mutation and other prognostic factors.

Materials and methods. 60 patients with PTC treated in P.A. Herzen Moscow Oncology Research Institute during 2014–2016 were included in this prospective study. Selection of patients was based on the results of fine-needle aspiration biopsy and polymerase chain reaction. Study participants were randomized into 2 groups: the first one included 45 patients harboring BRAF V600E mutation, the second one included 15 patients who lack this mutation. The following prognostic factors were evaluated in postoperative period: histological subtype of PTC, tumor invasion into the capsule of thyroid gland, multicentricity, presence of metastases in regional lymph nodes and distant metastases, TNM stage. Statistical data analysis was carried out using GraphPad Prism software.

Results. Papillary thyroid cancer was diagnosed in 40 % of the patients, follicular thyroid cancer – in 60 % in both groups. Tumor invasion into the capsule of thyroid gland was identified in 88 and 40 % of the cases in the first and second group respectively; thyroid capsular invasion – in 26 and 10 %; multicentricity – in 20 and 10 %; microcarcinomas (0.3–1.0  cm) – in 57 and 60 %, metastasis to regional lymph nodes – in 40 and 30 %. 51 % of the patients in the first group were found to have pT1 thyroid cancer with tumor capsular invasion without spreading beyond. After surgical treatment 23 % of the patients from the first group had changes in tumor stage from cT1–2  to pT3 according to routine histological examination results. Distant metastases were observed in 5 % of the cases in the first group and in 10 % in the second group. We found a statistically significant association between BRAF (V600E) mutation and tumor invasion into the capsule of thyroid gland (p < 0.05). At the same time neither multicentricity nor metastases in regional lymph nodes were associated with BRAF-mutation (p > 0.05). Conclusions. BRAF mutation in patients with PTC is associated with tumor invasion into the capsule of thyroid gland; this should imply the use of more aggressive treatment strategy (surgery). Further studies are needed to clarify the existing data.

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