Baranski, Thomas

AbstractBackgroundPrognosis among patients with differentiated thyroid cancer is widely variable. Better understanding of biologic subtypes is necessary to stratify patients and improve outcomes.MethodsIn patients diagnosed with classic histology papillary thyroid cancer treated from 1973 to 2009, BRAF V600E mutation status was determined on surgical tumor specimens by restriction fragment length polymorphism analysis. A tissue microarray (TMA) was constructed from tumor specimens in triplicate and stained by immunohistochemistry for RET, phospho‐MEK, MAPK(dpERK), PPARγ, and phospho‐AKT(pAKT). Stained slides were scored independently and blindly by two investigators and compared to tumor and patient characteristics and outcomes.ResultsA total of 231 patients had archived formalin‐fixed, paraffin‐embedded tumor tissue available and were included on the TMA. Mean age at diagnosis was 44 years (range 6‐82 years); proportion of patients with female sex was (72%); 2015 American Thyroid Association (ATA) risk stratification was low (26%), intermediate (32%), and high (42%). BRAF V600E mutation was found in 74% of specimens, and IHC was scored as positive for RET (61%), MAPK (dpERK) (14%), PPARγ (27%), and pAKT (39%). Positive RET staining was associated with a lower risk of recurrence (HR = 0.46, 95% CI 0.22‐0.96). No other molecular biomarkers were independent predictors of recurrence on univariable analysis. On RPA, patients with RET‐negative and either MAPK(dpERK)‐positive or pAKT‐positive tumors were identified to have a high risk of recurrence (HR = 5.4, 95%CI 2.5‐11.7). This profile remained associated with recurrence in a multivariable model including ATA risk stratification (HR = 2.8, 95% CI 1.3‐6.0).ConclusionCharacterization of molecular pathways involved in cPTC tumorigenesis may add further risk stratification for recurrence beyond the 2015 ATA risk categories alone.

The majority of papillary thyroid carcinoma (PTC) cases comprise classic papillary (C-PTC) and follicular variant (FV-PTC) histologic sub-types. Historically, clinical equivalency was assumed, but recent data suggest C-PTC may have poorer outcomes. However, large single-institution series with long-term outcomes of C-PTC and FV-PTC, using modern pathologic criteria for FV-PTC, are needed. Our objective was to compare prevalence and impact of clinicopathologic factors, including BRAF mutation status, on long-term outcomes of C-PTC and FV-PTC. We hypothesized that patients with C-PTC would have higher risk disease features and worse survival outcomes. This retrospective study included 1293 patients treated at a single, US academic institution between 1943 and 2009 with mean follow-up of 8.6 years. All patients underwent either partial or total thyroidectomy and had invasive C-PTC or FV-PTC per modern pathology criteria. Primary study measurements included differences in recurrence-free survival (RFS), disease-specific survival (DSS) and associations with clinicopathologic factors including the BRAF mutation. Compared to FV-PTC, C-PTC was associated with multiple features of high-risk disease ( P < 0.05) and significantly reduced RFS and DSS. Survival differences were consistent across univariate, multivariate and Kaplan–Meier analyses. BRAF mutations were more common in C-PTC ( P = 0.002). However, on Kaplan–Meier analysis, mutational status did not significantly impact RFS or DSS for patients with either histologic sub-type. C-PTC therefore indicates higher-risk disease and predicts for significantly poorer long-term outcomes when compared to FV-PTC. The nature of this difference in outcome is not explained by traditional histopathologic findings or by the BRAF mutation.