Researcher works on protocols to implement screening for gastric cancerApr. 2, 2020, 8:53 AM
by Tom Wilemon
A Vanderbilt gastroenterologist is helping lead an effort to establish screening guidelines for gastric cancer in the United States, where the number of people at risk for the cancer is increasing as the nation’s population becomes more diverse.
Worldwide, gastric cancer is the fifth most common cancer and third leading cause of cancer-related death. In the United States, gastric cancer ranks 15th among cancers, but it afflicts some population groups disproportionately.
Shailja Shah, MD, assistant professor of Medicine, is an author of multiple studies recently published in Gastroenterology, including a seminal cost-effectiveness analysis demonstrating that performing upper endoscopy for gastric cancer at age 50, bundled with colonoscopy for average risk colorectal cancer screening, is cost effective for non-white races/ethnicities — specifically, Hispanics, non-Hispanics blacks and Asian Americans. Shah and colleagues designed the model with the U.S. health care reimbursement structure in mind, given that anesthesia and facility fees/procedural time, add substantial additional costs.
“The major cost benefit of the model resulted from detection of early stage gastric neoplasia, which is most often asymptomatic, and would therefore not prompt an upper endoscopy,” Shah said. “Endoscopic or surgical resection at this early stage before it has spread into the deeper layers of the stomach and beyond is typically curative. This is in distinct comparison to when a person starts having symptoms, such as abdominal pain, weight loss, GI bleeding or others that prompt endoscopic evaluation. Once symptoms present, gastric cancer is typically at a more advanced stage, where therapeutic options are limited at best and, therefore, the chance of surviving five years is much poorer, about 30%. This is the more common scenario in the United States since we don’t screen.”
The main point of screening and surveillance is to obtain earlier diagnoses that enable better therapeutic options — ideally curative ones — that are directly associated with improved outcomes with respect to morbidity and mortality.
“The concept is similar to a colonoscopy for colorectal cancer screening and prevention: if we see a polyp, we can remove the polyp and prevent progression to cancer. Or, if we do diagnose a cancer on a screening colonoscopy, it’s hopefully at an earlier stage than had that person developed symptoms prompting a diagnostic as opposed to a screening exam,” Shah said. “It’s a similar concept in the stomach, especially now that we have the ability to resect lesions endoscopically if caught early enough.”
Shah was one of the lead members of the American Gastroenterology Association’s Technical Review team on gastric intestinal metaplasia surveillance for early gastric cancer detection.
The group’s work resulted in five separate papers on the scientific basis for establishing gastric cancer surveillance guidelines for the U.S. These articles were published collectively in last month’s print and online issue of Gastroenterology. The team’s work formed the foundation for the first evidence-based guideline on gastric intestinal metaplasia (precancer) management in the U.S.
Shah is also collaborating with a team of investigators nationally to compile the evidence needed to lobby for formalized national gastric cancer screening guidelines for high-risk populations, including racial/ethnic minorities and immigrants from countries where gastric cancer is endemic.
This will help with standardization of selection criteria, Shah said, but also to secure insurance coverage for upper endoscopy as part of routine cancer prevention and healthcare maintenance.
Gastric cancer is endemic in areas of Asia and Latin America, where many people have been infected early in life with the bacterium Helicobacter pylori, which is generally accepted to be the primary trigger for the process that leads to the most common type of gastric cancer.
Precancerous mucosal changes, such as gastric intestinal metaplasia, might occur as a result of chronic H. pylori infection, and these mucosal changes identify someone as at a significantly higher risk for gastric cancer.
“The fact that there are precancerous mucosal changes that occur and that are easily diagnosed on routine histopathology is one key reason why endoscopic screening/surveillance works.
In a very small portion of people these precancerous changes progress to cancer slowly over time, and this affords us the opportunity to diagnose cancers much earlier in these high-risk individuals compared to a no screening/- surveillance approach, which is the current norm.”
The prevalence of H. pylori infections is much lower in the U.S. than it was decades ago because of factors including improved sanitation and targeted eradication therapy campaigns.
“It is still the most common chronic bacterial infection worldwide,” Shah said. “While the U.S. is generally considered a low prevalence country, there are clear differences based on the population with non-white racial/ethnic groups, people of lower socioeconomic status and certain immigrant populations at higher risk.”
There are also factors other than chronic H. pylori infection that put people at increased risk, including diet, smoking and family history, Shah said.
“Stomach cancer really has been overlooked in the U.S.,” she said. “It is a potentially preventable and curable cancer, and it is a cancer that is screened for in some high-incidence countries like Japan and South Korea with impressive declines in related mortality. Considering that more than 45 million foreign-born individuals live in the U.S., with over 1 million arriving annually and from areas of high gastric cancer incidence, it is pretty clear that we need to do better. We need to act now to turn the tide of this disease.”