Taiji Matsuo

Low Prevalence of Helicobacter pylori-negative Gastric Cancer among Japanese

Background and Aims:  The true prevalence of Helicobacter pylori‐negative gastric cancer (HpNGC) is unknown. We attempt to clarify the prevalence and clinicopathologic features of HpNGC in Japanese.

Clinical prevention of gastric cancer by Helicobacter pylori eradication therapy: a systematic review

Helicobacter pylori (H. pylori) infection plays an important role in gastric carcinogenesis. We conducted a systematic review concerning gastric cancer development after H. pylori eradication therapy. In total 15 papers matched our criteria, the results were reviewed. The H. pylori eradication therapy statistically diminished the prevalence of clinical gastric cancer by approximately one-third. The studies from Japan supported this conclusion; however, studies from overseas reported conflicting results. The differences in these conclusions lie in the diagnostic ability of endoscopic examination, since the clinical stage was quite different between these studies. Gastric cancer that developed after eradication revealed a mainly intestinal type histology and depressed-type appearance. The following are possible reasons for reduced gastric cancer: (1) eradication therapy inhibits the new occurrence of gastric cancer, (2) eradication regresses or inhibits the growth of gastric cancer, and (3) eradication interferes with the discovery of gastric cancer. Considering the biological nature of cancer cell proliferation, a sufficiently long-term follow-up may clarify the effect of eradication therapy on inhibition of the development (not discovery) of gastric cancer and reduction of gastric cancer-related mortality.

Gastric Cancer Development after Helicobacter pylori Eradication Therapy: A New Form of Gastric Neoplasia

Background and Aim: Along with the widespread use of eradication for Helicobacter pylori (H. pylori), the incidence of gastric cancer after eradication has also been increasing. There is a need for clarification of the clinical and biological characteristics of these neoplasms. Patients and Methods: We studied 27 cases of gastric cancer that developed after eradication (group AE). Out of the 27, we selected 26 with early-stage gastric cancer and compared them with 78 age-matched gastric cancer patients with H. pylori infection (group Pos) and 20 patients without H. pylori (group Neg). The patient with autoimmune gastritis was not included. Clinicopathological features, mucus patterns and Wnt5a expressions were compared among these groups. Results: Among group AE patients, there were more males than females, and the tumor histology was mainly intestinal type, a significant difference from group Neg. In contrast, macroscopically, the tumors were predominantly of the flat-depressed type, a feature similar to that of group Neg but significantly different from that of group Pos. MUC2 and Wnt5a expression was significantly lower in group AE than in group Pos. Conclusion: Gastric cancer development after eradication may have a carcinogenic pathway similar to that in cancer with H. pylori infection, though macroscopic/biological features may be modified by eradication therapy.

Advanced Method for Evaluation of Gastric Cancer Risk By Serum Markers: Determination of True Low-Risk Subjects for Gastric Neoplasm

Patients with negative anti‐Helicobacter pylori antibody titer and high pepsinogen (PG) level (group A) are regarded as having a low risk for gastric cancer. However, gastric cancer cases are occasionally observed in this group. We aimed to elucidate the clinical features of gastric neoplasm in group A patients and reviewed advanced methods for mass screening.

Characteristic Epithelium with Low‐Grade Atypia Appears on the Surface of Gastric Cancer after Successful Helicobacter pylori Eradication Therapy

The incidence of gastric cancer after successful Helicobacter pylori eradication has been increasing. We previously reported that epithelium with low‐grade atypia (ELA) appeared on the surface of gastric cancer after H. pylori eradication. Here, we investigate the clinical and biological characteristics of such ELA.

A computer system to be used with laser-based endoscopy for quantitative diagnosis of early gastric cancer.

Goals: To evaluate the usefulness of a newly devised computer system for use with laser-based endoscopy in differentiating between early gastric cancer, reddened lesions, and surrounding tissue. Background: Narrow-band imaging based on laser light illumination has come into recent use. We devised a support vector machine (SVM)-based analysis system to be used with the newly devised endoscopy system to quantitatively identify gastric cancer on images obtained by magnifying endoscopy with blue-laser imaging (BLI). We evaluated the usefulness of the computer system in combination with the new endoscopy system. Study: We evaluated the system as applied to 100 consecutive early gastric cancers in 95 patients examined by BLI magnification at Hiroshima University Hospital. We produced a set of images from the 100 early gastric cancers; 40 flat or slightly depressed, small, reddened lesions; and surrounding tissues, and we attempted to identify gastric cancer, reddened lesions, and surrounding tissue quantitatively. Results: The average SVM output value was 0.846±0.220 for cancerous lesions, 0.381±0.349 for reddened lesions, and 0.219±0.277 for surrounding tissue, with the SVM output value for cancerous lesions being significantly greater than that for reddened lesions or surrounding tissue. The average SVM output value for differentiated-type cancer was 0.840±0.207 and for undifferentiated-type cancer was 0.865±0.259. Conclusions: Although further development is needed, we conclude that our computer-based analysis system used with BLI will identify gastric cancers quantitatively.

Diagnosis of Helicobacter pylori-induced gastritis by serum pepsinogen levels.

Gastric cancer develops due to atrophic gastritis induced by Helicobacter pylori (H. pylori) infection. Serum levels of pepsinogen (PG) are known to be excellent markers for evaluating the degree of atrophic gastritis. We investigated whether chronic gastritis could be diagnosed by evaluating serum PG levels.

Quantitative identification of mucosal gastric cancer under magnifying endoscopy with flexible spectral imaging color enhancement

Magnifying endoscopy with flexible spectral imaging color enhancement (FICE) is clinically useful in diagnosing gastric cancer and determining treatment options; however, there is a learning curve. Accurate FICE‐based diagnosis requires training and experience. In addition, objectivity is necessary. Thus, a software program that can identify gastric cancer quantitatively was developed.

Characteristics of Metachronous Gastric Tumors after Endoscopic Submucosal Dissection for Gastric Intraepithelial Neoplasms

Background. Recently, endoscopic submucosal dissection (ESD) has become a standard treatment method for early gastric cancer and concurrent stomach preservation. However, metachronous recurrences have become a major problem. We evaluated the incidence and clinicopathologic features of and examined the risk factors for metachronous gastric tumors. Methods. A total of 357 patients who underwent ESD for gastric tumors (245 early gastric cancers and 112 adenomas) and were followed up for more than 12 months without recurrence within the first 12 months were enrolled. We investigated the incidence and clinicopathologic features of metachronous tumors after ESD. We also analyzed the potential risk factors for metachronous tumors using the Kaplan-Meier method and Coxs proportional hazards model. Results. The annual incidence of metachronous tumors after ESD was 2.4%. The median period until discovery after initial ESD was 26.0 months, and the median observation period was 52.6 months. Male patients developed metachronous tumors more frequently (P = 0.04), and the hazard ratio of female to male patients was 0.36 (95% confidence interval: 0.11–0.89). Conclusions. Patients with a previous history of gastric tumors have a high risk of subsequent gastric tumor development and male patients should be carefully followed up after ESD for gastric tumor.

Labeling colorectal NBI zoom-videoendoscope image sequences with MRF and SVM

In this paper, we propose a sequence labeling method by using SVM posterior probabilities with a Markov Random Field (MRF) model for colorectal Narrow Band Imaging (NBI) zoom-videoendoscope. Classifying each frame of a video sequence by SVM classifiers independently leads to an output sequence which is unstable and hard to understand by endoscopists. To make it more stable and readable, we use an MRF model to label the sequence of posterior probabilities. In addition, we introduce class asymmetry for the NBI images in order to keep and enhance frames where there is a possibility that cancers might have been detected. Experimental results with NBI video sequences demonstrate that the proposed MRF model with class asymmetry performs much better than a model without asymmetry.