Gastric cancer - An overview

Gastric cancer remains the second leading cause of cancer-related deaths worldwide. Apart from dietary factors, Helicobacter pylori is currently considered as one of the most important risk factors. The incidence of gastric cancer in Hong Kong is not high enough to justify population screening with upper endoscopy. Clinical features, however, can be quite non- specific. Patients may be asymptomatic, especially during early stage of the disease. Upper endoscopy should be considered in patients presenting with recent onset of ulcer-like symptoms, weight loss, symptoms of obstruction, bleeding or anaemia, especially if they are elderly. By the time clinical features of metastases are apparent, the disease would be beyond cure. In recent years, endoscopic ultrasonography and staging laparoscopy have greatly enhanced the pre-operative staging accuracy. Such information will be important if neoadjuvant chemotherapy is contemplated for advanced disease. At present, surgery remains the mainstay of potentially curative treatment. Post-operative adjuvant chemotherapy is not recommended unless on a proper trial basis. Early results of pre-operative neoadjuvant chemotherapy are encouraging but further studies are required to confirm its efficacy. For unresectable gastric cancer, various treatment options are available and selection has to be individualised.published_or_final_versio

Helicobacter pylori infection: the reduced need for ulcer surgery

The success of the eradication treatment for Helicobacter pylori in managing ulcer disease has further refined the indications for ulcer surgery. More patients are spared unnecessary surgery and its untoward sequelae. It is intriguing that surgery has been effective, given that Helicobacter pylori infection is the underlying culprit. Recent studies show that the prevalence of Helicobacter pylori infection remains high after a vagotomy but is more markedly reduced following a partial gastrectomy. Such a reduction may be due to the removal of distal stomach, which is the usual site of infection. In addition, bile appears to be bactericidal to Helicobacter pylori. The association between Helicobacter pylori infection and perforated duodenal ulcer has not been completely settled. A recent study demonstrates that male gender and positive Helicobacter pylori status are independent factors that are associated with recurrent duodenal ulcer after surgery for perforation. Hence, eradication therapy should be given to any patient who has a Helicobacter pylori infection, after surgery has been performed for perforated duodenal ulceration.published_or_final_versio

E-cadherin and gastric cancer: Cause, consequence and applications

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EUS could detect ascites missed by CT scan [4]

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A new regularized TVAR-based algorithm for recursive detection of nonstationarity and its application to speech signals

This paper develops a new recursive nonstationarity detection method based on time-varying autoregressive (TVAR) modeling. A local likelihood estimation approach is introduced which gives more weights to observations near the current time instant but less to those distance apart. It thus allows the Wald test to be computed based on RLS-type algorithms with low computational cost. A reliable and efficient state regularized variable forgetting factor (VFF) QR decomposition (QRD)-based RLS (SR-VFF-QRRLS) algorithm is adopted for estimation for its asymptotically unbiased property and immunity to lacking of excitation. Advantages of the proposed approach over conventional approaches are 1) it provides continuous parameter estimates and the corresponding stationary intervals with low complexity, 2) it mitigates low excitation problems using state regularization, and 3) stationarity at different scales can be detected by appropriately choosing a certain window size. The effectiveness of the proposed algorithm is evaluated by testing vocal tract changes in real speech signals. © 2012 IEEE.published_or_final_versio

Phenotype and management of patients with familial adenomatous polyposis in Hong Kong: perspective of the Hereditary Gastrointestinal Cancer Registry.

OBJECTIVES: To report on the phenotypic spectrum and clinical management of Chinese patients suffering from the rare autosomal dominant colorectal cancer syndrome of familial adenomatous polyposis. DESIGN: Analysis of prospectively collected data from the database of a regional registry. SETTING: The Hereditary Gastrointestinal Cancer Registry, Hong Kong. PARTICIPANTS: One hundred and eight patients with proven familial adenomatous polyposis from 36 local Chinese families with the condition recruited to the Registry from 1995 to 2001. INTERVENTIONS: Screening programme for at-risk family members, prophylactic surgery at presymptomatic diagnosis, and surveillance programme for extracolonic lesions in affected individuals. MAIN OUTCOME MEASURES: Rate of colorectal cancer, type of surgical treatment, spectrum of extracolonic lesions, and management of the syndrome. RESULTS: Fifty patients suffered from colorectal cancer with a mortality rate of 78.0%. The strategy of presymptomatic diagnosis by screening and appropriate prophylactic surgery reduced the incidence of colorectal cancer. Affected individuals were prone to develop potentially serious extracolonic lesions including thyroid cancer (5.7%), desmoid tumour (15.7%), gastroduodenal adenomas (7.1%), duodenal microadenoma (17.1%), and pouch polyposis (17.4%). CONCLUSIONS: Screening and prophylactic surgery are effective ways to prevent colorectal cancer for patients with familial adenomatous polyposis. Lifelong regular surveillance is necessary to detect and manage extracolonic lesions. A dedicated registry is essential to coordinate clinical management and to compile data for furthering knowledge of this rare but complex syndrome.published_or_final_versio

Patients with Helicobacter pylori positive and negative duodenal ulcers have distinct clinical characteristics

Aim: To assess the clinical characteristics of Helicobacter pylori (H pylori) negative duodenal ulcer. Methods: Patients with an endoscopic diagnosis of duodenal ulcer between 1996 and 2002 were included in the present study. Patients were considered to be negative for H pylori, if both histological examination and rapid urease test of biopsy specimens were negative. A comparison was made between patients with H pylori positive and negative duodenal ulcers. Results: A total of 1 343 patients were studied. Their mean age was 54.7±0.5 years. There was a male preponderance (M:F = 2.5:1). Three hundred and ninety-eight patients (29.6%) did not have H pylori infection. The annual proportion of patients with H pylori negative duodenal ulcers increased progressively from 1996 to 2002. On multivariate analysis, patients with H pylori negative duodenal ulcer were more likely to be older, have concomitant medical problem, pre-existing malignancy, recent surgery, underlying sepsis, or taken non-steroidal anti-inflammatory drugs. In terms of clinical presentations, patients with H pylori negative duodenal ulcer were more likely to present with bleeding, multiple ulcers and larger ulcers. Conclusion: The proportion of patients with H pylori negative duodenal ulcers is on the rise because of a continued drop in incidence of H pylori positive duodenal ulcers in recent years. Such patients have distinct clinical characteristics and it is important to ascertain the H pylori status before starting eradication therapy. © 2005 The WJG Press and Elsevier Inc. All rights reserved.published_or_final_versio

A new recursive algorithm for time-varying autoregressive (TVAR) model estimation and its application to speech analysis

This paper proposes a new state-regularized (SR) and QR decomposition based recursive least squares (QRRLS) algorithm with variable forgetting factor (VFF) for recursive coefficient estimation of time-varying autoregressive (AR) models. It employs the estimated coefficients as prior information to minimize the exponentially weighted observation error, which leads to reduced variance and bias over traditional regularized RLS algorithm. It also increases the tracking speed by introducing a new measure of convergence status to control the FF. Simulations using synthetic and real speech signals show that the proposed method has improved tracking performance and reduced estimation error variance than conventional TVAR modeling methods during rapid changing of AR coefficients. © 2012 IEEE.published_or_final_versionThe 2012 IEEE International Symposium on Circuits and Systems (ISCAS), Seoul, Korea, 20-23 May 2012. In IEEE International Symposium on Circuits and Systems Proceedings, 2012, p. 1026-102

A New Variable Regularized QR Decomposition-Based Recursive Least M-Estimate Algorithm-Performance Analysis and Acoustic Applications

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A new switch-mode noise-constrained transform domain NLMS adaptive filtering algorithm

The transform domain normalized least mean squares (TDNLMS) algorithm is an efficient adaptive algorithm, which offers fast convergence speed with a reasonably low arithmetic complexity. However, its convergence speed is usually limited by the fixed step-size so as to achieve a low desired misadjustment. In this paper a new switch-mode noise-constrained TDNLMS (SNC-TDNLMS) algorithm is proposed. It employs a maximum step-size mode in initial convergence and a noise-constrained mode afterwards to improve the convergence speed and steady-state performance. The mean and mean square convergence behaviors of the proposed algorithm are studied to characterize its convergence condition and steady-state excess mean square error (EMSE). Based on the theoretical results, an automatic threshold selection scheme for mode switching is developed. Computer simulations are conducted to show the effectiveness of the proposed algorithm and verify the theoretical results. © 2011 IEEE.published_or_final_versionThe 2011 IEEE International Symposium on Circuits and Systems (ISCAS), Rio de Janeiro, Brazil, 15-18 May 2011. In Proceedings of ISCAS, 2011, p. 117-12