Calculating Stage Duration Statistics in Multistage Diseases

Many human diseases are characterized by multiple stages of progression. While the typical sequence of disease progression can be identified, there may be large individual variations among patients. Identifying mean stage durations and their variations is critical for statistical hypothesis testing needed to determine if treatment is having a significant effect on the progression, or if a new therapy is showing a delay of progression through a multistage disease. In this paper we focus on two methods for extracting stage duration statistics from longitudinal datasets: an extension of the linear regression technique, and a counting algorithm. Both are non-iterative, non-parametric and computationally cheap methods, which makes them invaluable tools for studying the epidemiology of diseases, with a goal of identifying different patterns of progression by using bioinformatics methodologies. Here we show that the regression method performs well for calculating the mean stage durations under a wide variety of assumptions, however, its generalization to variance calculations fails under realistic assumptions about the data collection procedure. On the other hand, the counting method yields reliable estimations for both means and variances of stage durations. Applications to Alzheimer disease progression are discussed

BRAF Rearrangements and BRAF V600E mutations are seen in a subset of pancreatic carcinomas with acinar differentiation

Context.\u2014: Comprehensive genomic profiling has demonstrated that approximately 20% of pancreatic carcinomas with acinar differentiation harbor potentially targetable BRAF fusions that activate the MAPK pathway. Objectives.\u2014: To validate the above finding by BRAF break-apart fluorescence in situ hybridization (FISH) in a large series of pure acinar cell carcinomas (ACCs), evaluate tumors for the presence of BRAF V600E mutations, and compare clinicopathologic features of tumors with BRAF rearrangements with those without. Design.\u2014: Thirty cases of pure ACC and 6 cases of mixed acinar-neuroendocrine carcinoma (ACC-NEC) were retrieved. A break-apart FISH probe was used to detect BRAF rearrangements. Immunohistochemistry for BRAF V600E was performed. Results.\u2014: BRAF rearrangements by FISH were found in 6 of 36 cases (17%), 5 of which were pure ACC and 1 was a mixed ACC-NEC. Follow-up was available in 29 of 36 (81%). The median survival was 22 months for BRAF-rearranged cases and 16 months for BRAF-intact cases; the 2-year overall survival was 50% for BRAF-rearranged cases and 35% for BRAF-intact cases. No significant clinicopathologic differences were identified in cases with BRAF rearrangement compared with those without BRAF rearrangement. BRAF V600E mutation was identified in 2 of 34 cases (6%), both of which were pure ACC and were BRAF-intact by FISH. Conclusions.\u2014: This study supports the finding that BRAF rearrangements are present in approximately 20% of cases and identified BRAF V600E mutations in approximately 5% of cases. These cases may benefit from targeted therapy

Molecular testing for the clinical diagnosis of fibrolamellar carcinoma

WOS: 000419766500013PubMed ID: 28862261Fibrolamellar carcinoma has a distinctive morphology and immunophenotype, including cytokeratin 7 and CD68 co-expression. Despite the distinct findings, accurate diagnosis of fibrolamellar carcinoma continues to be a challenge. Recently, fibrolamellar carcinomas were found to harbor a characteristic somatic gene fusion, DNAJB1-PRKACA. A break-apart fluorescence in situ hybridization (FISH) assay was designed to detect this fusion event and to examine its diagnostic performance in a large, multicenter, multinational study. Cases initially classified as fibrolamellar carcinoma based on histological features were reviewed from 124 patients. Upon central review, 104 of the 124 cases were classified histologically as typical of fibrolamellar carcinoma, 12 cases as 'possible fibrolamellar carcinoma' and 8 cases as 'unlikely to be fibrolamellar carcinoma'. PRKACA FISH was positive for rearrangement in 102 of 103 (99%) typical fibrolamellar carcinomas, 9 of 12 'possible fibrolamellar carcinomas' and 0 of 8 cases 'unlikely to be fibrolamellar carcinomas'. Within the morphologically typical group of fibrolamellar carcinomas, two tumors with unusual FISH patterns were also identified. Both cases had the fusion gene DNAJB1-PRKACA, but one also had amplification of the fusion gene and one had heterozygous deletion of the normal PRKACA locus. In addition, 88 conventional hepatocellular carcinomas were evaluated with PRKACA FISH and all were negative. These findings demonstrate that FISH for the PRKACA rearrangement is a clinically useful tool to confirm the diagnosis of fibrolamellar carcinoma, with high sensitivity and specificity. A diagnosis of fibrolamellar carcinoma is more accurate when based on morphology plus confirmatory testing than when based on morphology alone.NIDDK NIH HHSUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute of Diabetes & Digestive & Kidney Diseases (NIDDK) [P30 DK026743