Effect of Buparlisib, a Pan-Class I PI3K Inhibitor, in Refractory Follicular and Poorly Differentiated Thyroid Cancer.

BACKGROUND: Dysregulation of the phosphatidylinositol 3-kinase (PI3K) pathway is frequent in advanced follicular (FTC) and poorly differentiated thyroid (PDTC) carcinomas and has been implicated in oncogenesis and tumor progression. This study investigated the efficacy and safety of buparlisib, a pan-PI3K inhibitor in radioiodine refractory FTC and PDTC. METHODS: The primary endpoint of this open-label, multicenter, phase 2 pilot study was progression-free survival (PFS) at 6 months. The sample size was determined considering that a PFS ≤50% at 6 months would denote an absence of benefits (null hypothesis). Secondary endpoints were objective response rate, PFS at 12 months, overall survival at 6 and 12 months, and safety based on the frequency and severity of adverse events (AEs). RESULTS: Forty-three patients (19M/24 F; median age: 67 years) with metastatic, radioiodine refractory, progressive disease received buparlisib, 100 mg, daily. Histology was PDTC in 25 (58%), FTC in 17 (40%), and Hürthle cell carcinoma in 1 (2%). RAS mutation was found in 44% (12/27) and activation of the PI3K pathway in 35% (8/23) of tested tumors. The probability of PFS was 41.7% [95% confidence interval (CI) 7.7-55.5] at 6 months and 20.9% [CI 0-35.7] at 12 months, lower than the 50% expected PFS. At 6 months, 25.6% patients had stable disease, 48.8% were progressive and 25.6% had stopped treatment due to AE. The response to therapy was not influenced by age, sex, histology, or genetic alterations. The overall survivals at 6 and 12 months were 85.9% [CI 76-97] and 78.7 % [CI 67-92], respectively. The mean tumor growth rate decreased from 3.78 mm/month [CI 2.61-4.95] before treatment to 0.8 mm/month [CI -0.2-1.88] during treatment (p < 0.02). Severe grade 3-4 AEs occurred in 27 patients (63%), including hepatitis (25%), hyperglycemia (21%), mood disorders (12%), and skin toxicity (12%), with favorable outcome after temporary or permanent treatment discontinuation or dose reduction. CONCLUSIONS: Buparlisib did not result in significant efficacy in advanced FTC and PDTC. However, the decrease in tumor growth rate may suggest incomplete inhibition of oncogenic pathways and/or escape mechanisms. This should lead to evaluate combined therapy associating inhibitors of both the PI3K and mitogen-activated protein kinase pathways.

Predictive factors of outcome in poorly differentiated thyroid carcinomas.

BACKGROUND: The prognosis of poorly differentiated thyroid carcinomas (PDTC) is heterogeneous though generally poor. The objectives of this study were to identify clinical and molecular factors of poor prognosis. METHODS: One hundred four consecutive patients treated for a PDTC between 01/01/2000 and 31/12/2010 were included in this study. A pathological review was done for all cases (blinded to clinical data and outcome). RESULTS: All patients underwent thyroidectomy. Adjuvant radioactive-iodine was administered in 95.2% of them. Tumours were pT3 or pT4 in 68.3% of cases and metastatic in 38.5% of patients. Extrathyroidal extension (ETE) was observed in 40% of patients. At the end of the initial treatment, only 37% of patients were considered in remission. Fifty-two patients (50%) became refractory to radioiodine during follow-up. The 5-year overall survival was 72.8% and the 5-year recurrence-free survival (RFS) was 45.3%. Remission after initial treatment was an independent factor of RFS (HR = 0.22; [0.10-0.49]). ETE was the only significant parameter influencing the overall survival in multivariate analysis. TERT promoter mutations at positions -124 (C228T) and -146 (C250T) were present in 38.1% of analysed patients and significantly associated with radioiodine resistance but not with overall survival. Half of TERT promoter mutant tumours harboured also RAS or BRAF mutations. CONCLUSION: PDTC form a heterogeneous group of patients with usual late-stage diagnosis, low radioactive iodine avidity and frequent metastatic spread. TERT promoter mutations could help to identify patients with high risk of radio-iodine refractoriness.