A common stomach bug may lower the risk of one oesophageal cancer
Oesophageal cancer comes in two main forms with almost opposite profiles. One tracks tobacco, alcohol and scalding drinks and dominates in poorer countries; the other follows acid reflux and obesity in richer ones. Oddly, infection with Helicobacter pylori, a stomach bacterium blamed for gastric cancer, is linked with lower risk of the second.
In 2018 the disease was the eighth most common cancer worldwide, with 572,000 new cases and about 509,000 deaths, up from 345,000 deaths in 1990. Roughly half of all cases occur in China, and men are affected about three times as often as women. Because noticeable symptoms, chiefly trouble swallowing solid food, tend to appear only once a tumour has spread around more than 60% of the tube's circumference, diagnosis often comes late. Five-year survival in the United States is around 22%.
Squamous-cell carcinoma grows from the flat cells lining the oesophagus. Alcohol and tobacco are its two big drivers and act together far more strongly than either alone; some data attribute about half of cases to tobacco and a third to alcohol. Drinks hotter than 65 °C, nitrosamines in smoked, pickled or barbecued foods, and chewing betel nut in parts of Asia also raise risk. Alcohol's effect seems to run through its aldehyde breakdown product and enzyme variants that are fairly common in Asia.
Adenocarcinoma begins in glandular cells in the lower third of the tube. Long-standing reflux can make the lining switch to an intestinal cell type, a condition called Barrett's oesophagus, which raises the chance of later cancer, though that risk may once have been overstated. Researchers have traced the switch to a small compartment of cells expressing the gene HOXA13, which tolerates acid and bile better than normal lining and gradually outcompetes it. Excess weight, especially around the abdomen, shows possibly the strongest link of any obesity-related cancer, and men are 7 to 10 times more likely than women to develop this type.
The H. pylori puzzle is unresolved. The infection causes reflux, yet it is associated with up to 50% lower adenocarcinoma risk, perhaps because some strains cut stomach acid. Falling infection rates in Western countries, tied to less crowded homes, may be one reason this cancer has become more common there.
Source: Esophageal cancer
