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Incidence of esophageal adenocarcinoma increasing dramatically worldwide
Esophageal adenocarcinoma has become more prevalent during the past several decades, with the onset and magnitude of this increase varying even between neighboring countries and states, according to recent results.
Researchers evaluated data on 117,946 incident cases of esophageal adenocarcinoma collected from cancer registries in North America, Europe, Australia and Asia. Incorporated information was dated from 1955 through 2009 and included the number of diagnosed cancers per calendar year, within age groups at 5-year increments and according to sex. Ninety-nine percent of cases occurred in patients aged 40 years or older, and 22.3% occurred in women.
Overall, the age-adjusted incidence rates of esophageal adenocarcinoma increased during the study period. The annual proportional increase ranged from 3.5% observed in Scotland to 8.1% in Hawaii, and joinpoint analyses performed for evaluable registries indicated potential starting points for the increase ranging from 1976 in Denmark (average change per decade=0.26 per 100,000 person-years before joinpoint, 0.61 after, P<.05) to 1991 in Sweden (0.12 per 100,000 person-years before joinpoint, 0.74 after, P<.0001).
In most cases, the rate increase was proportionally similar between men and women, but men developed the illness three to six times more frequently overall, with rates seven to nine times greater among men than women in the US, specifically.
Incidence rates in men typically mimicked one of the following calendar period patterns:
- An initial phase with a steady rate of one or less cases per 100,000 person-years, followed by a second phase with a monotonic increase by one to two cases per 100,000 person-years per decade
- A continuous increase of roughly two to three cases per 100,000 person-years per decade throughout the evaluated period
Cases among women were less frequent and more prone to random fluctuations, but followed a largely similar pattern. Investigators also noted that, with one exception, the data series for areas fitting the second pattern began with incidence rates at or above those reported during the initial phases of the areas fitting the first pattern.
“While changes in the exposure prevalence to known major risk factors and mis- or reclassification of other malignancies in the esophagus and proximal part of the stomach have likely contributed to an increasing incidence of esophageal adenocarcinoma, they are unlikely to explain neither the abrupt change nor the astounding rate of increase,” the researchers wrote. “Therefore, it seems reasonable to hypothesize that effects of a strong, highly prevalent and yet unidentified causal factor … are superimposed on the effects of known risk factors. The obvious variation in time of onset of the epidemic and the uneven distribution among sexes may provide important clues as to the nature of this exposure.”
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In considering esophageal cancer, obviously swallowed material is high on the list of possible entities that might be involved in this "epidemic." I know of no other ingestant that has reached more massive new use in the past few decades than diet beverages. I believe this could be a fruitful (pun to be ignored) area of investigation.
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The study by Edgren and colleagues is provocative. They conducted a comparative analysis of multiple population-based cancer registries, and concluded that the year the incidence of esophageal adenocarcinoma began increasing ranged from the 1960s to the 1990s in different countries, with wide variation in the start, even between neighboring Scandinavian countries.
One of the major risk factors for the cancer is obesity, and the most commonly-held hypothesis accounting for the rising incidence has been the obesity epidemic. But the authors found that the timing of the rise of the cancer does not match the timing of the rise of obesity in the different countries.
Drawing conclusions from such an ecological analysis is difficult, but their study at least raises the possibility that some other unknown factor that was introduced in the affected countries between the 1960s and the 1990s may be responsible for the rising incidence of esophageal adenocarcinoma.
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The increasing incidence of esophageal adenocarcinoma now has been shown to be true in the entire western world. Even in Asian countries, where it was unheard of, this cancer is now being recognized more frequently.
What accounts for this increase? Is there a single established etiology that can be blamed? Unfortunately, like with other common diseases and cancer, there is no single explanation as of now. With the rise of acid reflux disease (GERD), obesity, change in diet and decreasing H. pylori rates - it appears that all of these have played a role in this disease.