By: Jean Johnson for Reflux1While people on both sides of the world suffer from esophageal cancer, the underpinnings of each region’s problems are markedly different. That’s why in China scientists have their eyes on zinc, and in the States, one group of researchers took a look at selenium.
Esophageal cancers arise from different sources. Flat, fish scale-like cells found in the lining of the body’s passages and hollow organs can give rise to what’s known as squamous cell carcinomas. Esophageal squamous carcinoma. That’s the term researchers give to esophageal cancers that currently predominate in China. These are cancers that may decrease when adequate zinc levels are present.
The other form, esophageal adenocarcinoma, arises from cells in the lining of the digestive tract that have glandular, or secretory, properties. Esophageal adenocarcinoma has risen dramatically in the United States over the past three decades, and particularly the last 15 years. Researchers at the University of Washington (UW) looked at the major precursor to esophageal adenocarcinoma, Barrett’s Esophagus, and tentatively concluded that adequate selenium levels might lower risk.
Both studies came out in the Journal of the National Cancer Institute. The zinc study was the most recent in 2005. It followed 132 residents of Linzhou, China over a period of 20 years. Those with the highest levels of zinc were 79 percent less likely to develop esophageal squamous cancer than those with low levels of the mineral. The finding correlates with studies that showed zinc deficiencies in rodents predisposed the animals to esophageal cancers.
The UW study completed in 2003, followed 399 patients with Barrett’s Esophagus, the condition that currently plagues more that one million Americans and precedes most instances of esophageal adenocarcinoma. As did the China study, the UW research concluded that lower than normal levels of a particular trace mineral might somehow be a factor – although in this case the mineral was selenium, not zinc.
Why the difference? Why is China experiencing high rates of one type of esophageal cancer and the U.S. another?
“If we knew that,” said professor and vice chairman of surgery at Oregon Health Science University (OHSU), Brett C. Sheppard, MD, FACS, “we’d win the Nobel Prize.” That said, Sheppard does have some ideas.
“In most of the Western world squamous cell carcinoma is on the decline along with gastric cancer. Esophageal squamous cancer is associated with the male gender, more common in blacks than whites and more common in people who drink and smoke. More, although not always, it tends to be a lower socioeconomic disease,” said Sheppard. “The decline in squamous cell carcinoma of the esophagus probably does have a lot to do with altering behavioral patterns. But improvements in public health and other yet to be understood environmental factors most likely influence the incidence as well.”
As far as esophageal adenocarcinoma goes, Sheppard noted that “adenocarcinomas are found more in men than women, and the risk begins in middle age for most people. Reflux is a known risk factor for the development of Barrett’s, and subsequently of adenocarcinoma of the esophagus. Obesity, as well, contributes to the risk of developing malignancy in many organ systems and is believed to promote reflux, and thereby contribute to the development of adenocarcinoma.
“Then again, obesity may be acting in other ways as well such as altering the way the body metabolizes food,” Sheppard said. “Or obesity may just be a marker of dietary indiscretion of high animal fats and sugars which when metabolized promote the development of malignancy over a lifetime.”
Even with the physician’s qualification, it’s still like Bart Simpson saying, ‘duh, it’s what you eat, man.’ The problem is, though, it’s a damned if you do, damned if you don’t sort of puzzle.
In China where people are emerging into a market economy and still struggle to put food on the table, they seem to have the poor man’s version of esophageal cancer. And conversely in the States where MacDonald’s seem to be more prevalent than gas stations, folks are plagued by a variation on the theme.
But any way one slices it – East-West, rich-poor – esophageal cancer’s no fun. That’s why the National Cancer Institute’s work proceeds apace, even if the studies are focused on the painstaking work of turning over of stone after stone at the level of cells and trace minerals specific to global regions.
