The esophagus is the tube that goes from our throat down to our stomach and acts as a passageway for the food that we eat. As with other parts of the body, the tissues of the esophagus are not completely safe from cancer, and there are several types of esophageal cancer. The principal types are squamous cell carcinoma, which often arises in the upper half of the esophagus, and adenocarcinoma, which typically arises in the lower half. This difference in location, also means that in many cases the risk factors can be different for each of the subtypes.
Importantly, note that the incidence rate of esophageal cancer varies considerably with location (geographical differences), showing that genetic factors, lifestyle, and ethnicity all play a role in its development.
The focus of this article is to describe the various risk factors associated with esophageal cancer, understanding a risk factor as a characteristic, condition, or behavior that increases the likelihood of getting a disease. Note that risk factors are merely correlational, meaning that they only show the degree to which a pair of variables are related. However, they are not necessarily causal, because correlation does not prove causation.
The health risks associated with smoking are very well known, and the popularity of the habit has decreased dramatically in recent years. Still, a lot of people do choose to smoke, and some are having difficulty kicking the habit. A major risk factor for both subtypes of esophageal cancer is tobacco use (stronger for squamous cell carcinoma). When people smoke tobacco, they inhale many carcinogens (substances that can cause cancer) such as nitrosamines, aromatic amines, aldehydes, polycyclic aromatic hydrocarbons, and phenols. These can damage any cell they come into contact with, including those in the gastrointestinal, respiratory, and urogenital tract. Furthermore, many studies have reported that for squamous cell carcinoma (SCC) of the esophagus alcohol is the primary risk factor, but when combined with tobacco use they have a synergistic effect (greater combined effect).
Smoking also contributes to gastroesophageal reflux disease (GERD)and its complications, which are also risk factors for adenocarcinoma of the esophagus. It does so by relaxing the smooth muscle (lower esophageal sphincter or LES) that forms a tight ring in the connection between the stomach and the esophagus. The LES is going to regulate the passage of food into the stomach, preventing acid from backing up into the esophagus. Thus, if it relaxes, there is an increased risk of acid surging up and damaging the esophagus. Other ways by which smoking contributes to GERD are by reducing salivation, increasing acid secretion in the stomach, and interfering with the contraction of esophageal muscles.