Particle Gibbs Split-Merge Sampling for Bayesian Inference in Mixture Models

This paper presents a new Markov chain Monte Carlo method to sample from the posterior distribution of conjugate mixture models. This algorithm relies on a flexible split-merge procedure built using the particle Gibbs sampler. Contrary to available split-merge procedures, the resulting so-called Particle Gibbs Split-Merge sampler does not require the computation of a complex acceptance ratio, is simple to implement using existing sequential Monte Carlo libraries and can be parallelized. We investigate its performance experimentally on synthetic problems as well as on geolocation and cancer genomics data. In all these examples, the particle Gibbs split-merge sampler outperforms state-of-the-art split-merge methods by up to an order of magnitude for a fixed computational complexity

Neoadjuvant Chemotherapy in Patients with Stage IV Colorectal Cancer: A Comparison of Histological Response in Liver Metastases, Primary Tumors, and Regional Lymph Nodes

Background: We report the histopathological results of a novel "inversed” strategy designed to manage patients with colorectal cancer (CRC) who have synchronous liver metastases by using chemotherapy first, liver surgery second, and resection of the primary tumor as a final step. This study was designed to compare the response to chemotherapy in liver metastases, primary tumors, and locoregional lymph nodes. Methods: Twenty-nine patients with stage IV CRC received a combination of oxaliplatin, irinotecan, 5-fluorouracil, and leucovorin (OCFL) for 3-4months. Histological response to chemotherapy was assessed by using a tumor regression grading (TRG) score based on presence of residual tumor cells and extent of fibrosis. Results: Median age of patients was 56 (range, 37-69) years. Primary tumor location was right colon (n=5), left colon (n=7), and rectum (n=17 patients). TRG scores correlated across disease sites (Spearman correlation coefficients for TRG in the primary tumor and lymph nodes was 0.59 [P=0.005]; for the primary tumor and metastases 0.44 [P=0.021]; and for lymph nodes and metastases 0.58 [P=0.006]). Complete absence or poor tumor response (TRG4/5) was significantly more frequent in primary tumors (35.7%) and locoregional lymph nodes (38%) than in liver metastases (6.9%; McNemar test, P=0.02). Two patients had a complete pathologic response (pT0N0M0). Conclusions: In patients with stage IV colorectal cancer, liver metastases exhibit a better histological response than primary tumors to OCFL neoadjuvant chemotherap

Ablation of hepatocellular carcinoma by percutaneous ethanol injection: Imaging findings

Summary: Since PEI is a treatment based on imaging techniques, the radiologist should be familiar with the various findings that may be observed after PEI on US, CT, and MR images immediately after treatment and during later follow-up. Although US is well suited for performing PEI, contrast-enhanced CT currently is the most commonly used imaging method to evaluate the effect of PEI. Residual, nodular areas of contrast enhancement correlate well with residual tumor and warrant additional treatment. Although the findings on MR images obtained after PEI are more complex, MR imaging may be used as an alternative to C

Survival after Lung Metastasectomy in Colorectal Cancer Patients with Previously Resected Liver Metastases

Background: Resection of hepatic metastases is indicated in selected stage IV colorectal cancer (CRC) patients. A minority will eventually develop pulmonary metastases and may undergo lung surgery with curative intent. The aims of the present study were to assess clinical outcome and identify parameters predicting survival after pulmonary metastasectomy in patients who underwent prior resection of hepatic CRC metastases. Methods: We performed a retrospective analysis of 27 consecutive patients (median age 62years; range: 33-75years) who underwent resection of pulmonary metastases after previous hepatic metastasectomy from CRC in two institutions from 1996 to 2009. All patients underwent complete resection (R0) for both colorectal and hepatic metastases. Results: Median follow-up was 32months (range: 3-69months) after resection of lung metastases and 65months (range: 19-146months) after resection of primary CRC. Three- and 5-year overall survival rates after lung surgery were 56 and 39%, respectively, and median survival was 46months (95% CI 35-57). Median disease-free survival after pulmonary metastasectomy was 13months (95% CI 5-21). At the time of last follow-up, seven patients (26%) had no evidence of recurrent disease and 6 of these 7 patients presented initially with a single lung metastasis. Conclusions: Resection of lung metastases from CRC patients may result in prolonged survival, even after previous hepatic metastasectomy. Yet, prolonged disease-free survival remains the exception, and seems to occur only in patients with a single lung lesio

Improved Long-Term Outcome of Surgery for Advanced Colorectal Liver Metastases: Reasons and Implications for Management on the Basis of a Severity Score

Background: The outcome of liver resection for colorectal liver metastases (CRLM) appears to be improving despite the fact that surgery is offered to patients with more-severe disease. To quantify this assumption and to understand its causes we analyzed a series of patients on the basis of a standardized severity score and changes in management occurring over the years. Methods: Patients' characteristics, operative data, chemotherapies and follow-up were recorded. CRLM severity was quantified according to Fong's clinical risk score (CRS), modified to take into account the presence of bilateral liver metastases. Three periods were analyzed, in which different indications, surgical strategies and uses of chemotherapy were applied: 1984-1992, 1993-1998, and 1999-2005. Results: Between January 1984 and December 2005, 210 liver resections were performed in 180 patients (1984-1992, 43 patients; 1993-1998, 42 patients; 1999-2005, 95 patients). CRLM severity increased throughout the time periods, as did the use of neoadjuvant chemotherapies, repeat resections, and multistep procedures. While the disease-free survival did not improve over time, the 1-, 3- and 5-year overall survival rate increased from 85%, 30%, and 23% in the first period, to 88%, 60%, and 34% in the second period, and to 94%, 69%, and 46% in the third period. Conclusions: Analysis according to the CRS showed that despite the fact that patients had more severe disease, the overall survival improved over the years, mainly thanks to more aggressive treatment of recurrent disease. Management of advanced CRLM should, from the start, take into account the likelihood of secondary procedure

Pilot Anopheles gambiae full-length cDNA study: sequencing and initial characterization of 35,575 clones

We describe the preliminary analysis of over 35,000 clones from a full-length enriched cDNA library from the malaria mosquito vector Anopheles gambiae. The clones define nearly 3,700 genes, of which around 2,600 significantly improve current gene definitions. An additional 17% of the genes were not previously annotated, suggesting that an equal percentage may be missing from the current Anopheles genome annotation

A Comprehensive Spectral Analysis of the X-Ray Pulsar 4U 1907+09 from Two Observations with the Suzaku X-Ray Observatory

We present results from two observations of the wind-accreting X-ray pulsar 4U 1907+09 using the Suzaku observatory. The broadband time-averaged spectrum allows us to examine the continuum emission of the source and the cyclotron resonance scattering feature at ~19 keV. Additionally, using the narrow CCD response of Suzaku near 6 keV allows us to study in detail the Fe K bandpass and to quantify the Fe K beta line for this source for the first time. The source is absorbed by fully-covering material along the line of sight with a column density of NH ~2e22 /cm^2, consistent with a wind accreting geometry, and a high Fe abundance (~3-4 x solar). Time and phase-resolved analyses allow us to study variations in the source spectrum. In particular, dips found in the 2006 observation which are consistent with earlier observations occur in the hard X-ray bandpass, implying a variation of the whole continuum rather than occultation by intervening material, while a dip near the end of the 2007 observation occurs mainly in the lower energies implying an increase in NH along the line of sight, perhaps indicating clumpiness in the stellar wind.Comment: Accepted for publication in ApJ. 12 pages, 16 figure