The Historical Basis for the AEsophageal Cancer Belt of South-Central Asia
F. Saidi MD
Department of Surgery, Shahid Beheshti University of Medical Sciences, Tehran, Iran
On a worldwide basis, cancer of the esophagus is the ninth most common malignancy. In developing countries it ranks fifth in frequency and has one of the worst prognoses of any neoplasm of the human body. Because of its strategic location between the oral cavity and the stomach, the disease is usually incurable when the patient experiences difficulty in swallowing.
What is very disturbing and yet also fascinating about this malignancy, is the remarkable variation in its geographic incidence in different parts of the world. While the incidence of this disease in North America and Western Europe is about 5 to 10/100000, this figure is more than 100/100000 in Iran and some parts of China. These two countries constitute the two ends of what has become known as the "Esophageal Cancer Belt of South-Central Asia" an area that stretches from the Caucasian mountains across northern Iran, Afghanistan, Kazakhestan, Uzbekistan and Turkamanistan, into northern China. Extensive surveys in certain provinces of northern China initiated almost fifty years ago, and one or two reports from Iran some thirty years ago, plus sporadic reports from the newly established Republics of southern Russia, have substantiated the presence of this geographic "Cancer Belt". People living in this general region have a 20 fold greater chance of developing this disease than if they were living elsewhere.
Is there something in the environment, such as food, water, soil, plants or precipitation which act as a risk factor; or are people in this region genetically programmed to develop this disease. The mystery attached to the etiology of esophageal cancer is as deep as the geographic expanse of the "Esophageal Cancer Belt" is long and wide. Thus far no proven precursor or causative factor or factors have been found. What has become clear, however, is that the "Esophageal Cancer Belt of South-Central Asia" constitutes a ready made natural laboratory to study the basic phenomenon of this disease.
There is a reason for all things in nature. Hence, knowledge about the "Esophageal Cancer Belt of South-Central Asia" could be helpful in elucidating the relative role of environmental and genetic factors in the causation of this malignancy in man.
It is here where the history of medicine opens a new window on the subject. A historical perspective could provide valuable clues in clarifying the puzzle.
In the realm of history of the medicine, both China and Iran boast a rich heritage. It should not come as a surprise therefore, to discover that cancer of the esophagus has been mentioned by ancient medical writers in both of these countries:
Avicenna of Iran living in the "Esophageal Cancer Belt" between 980 to 1037 A.D. is said to have been the first physician to refer to this disease as "cancer of the esophagus" ("Saratan Be- Mery" in Farsi). What is astounding is that Avicenna, according to the discourses of his second generation pupil, Jorjani also described the symptoms of cancer of the esophagus.1 Jorjani, a prominent physician himself, lived between 1042-1136 A.D. in present day Gorgan in northeast Iran near the shores of the Caspian Sea, and was well versed in the teachings of his illustrious predecessor.
Moving to China, we encounter a number of references in ancient Chinese medical literature to this disease, going back to more than 2000 years ago. There, cancer of the esophagus was known as "Ye Ge". It is stated in the text of Yi-Guan as "commonly seen in the elderly and rarely developing in young people".2
It would be difficult not to reach the conclusion that cancer of the esophagus was a common condition in the centuries past in both China and Iran. By inference, the "Esophageal Cancer Belt of South-Central Asia" is a natural phenomenon with a background of at least one or two millennia.
The first step in such deductive reasoning is to wonder whether, what is diagnosed today as cancer of the esophagus on the basis of radiologic, endoscopic and histologic findings, is indeed the same condition referred to by ancient Chinese and Iranian physicians who had no access to modern medical technology. The symptomatology of this disease is helpful in this respect. Cancer of the esophagus invariably starts with difficulty in swallowing solids, then liquids, ending in total obstruction with death by inanition. This chain of events is so consistent that it cannot confuse the astute clinician, whether modern or ancient. It was, in fact, primarily on the basis of the clinical picture encountered by Iranian clinicians,3,4 about thirty years ago, that surveys were carried out in north Iran,5,6 establishing this geographic region as a high incidence areas for esophageal cancer.
The next step, more an inductive process, is to ask whether an accurate description of esophageal cancer by ancient Chinese and Iranian physicians, can be taken to mean a higher incidence of the disease in those areas in ancient days. Keeping in mind that epidemiology is a very modern science, how does one know that esophageal cancer was common one or two thousand years ago in the
"Esophageal Cancer Belt of South-Central Asia" area" More common, that is, in comparison to other cancers?
Only two other cancers can be diagnosed accurately by taking a medical history and doing a physical examination: skin (including the oral cavity) and breast. By inference, therefore, one is permitted to assume that what was described as esophageal cancer in historical times was indeed the same disease seen today.
The final question, however, is one that cannot be answered at this time without extensive research: how can one use historical evidence for the existence of an "Esophageal Cancer Belt of South-Central Asia" to support either environmental or hereditary risk factors in the etiology of this disease? Knowing something about the history of medicine might help but will not necessarily solve the riddle of esophageal cancer, something which must have been a mystery even to our brilliant medical forefathers.
References
1 Ghadirian P. An epidemiologic study of esophageal cancer with particular reference to northern Iran. PhD Thesis. 1982; London University, Institute of Cancer Research, Division of Epidemiology, Sutton, Surrey.
2 Qian ZX. Investigations on esophageal cancer in the province of Xinjiang (in Chinese). Collected Papers of the Second Symposium on Esophageal Carcinoma. 1961; Chinese Academy of Medical Sciences:74-8.
3 Habibi A. Cancer in Iran. A survey of the most common cases. J Nat Cancer Inst 1965; 34:553-69.
4 Haghighi P, Nabizadeh I, Asvadi SH, Mohallatee EA. Cancer in Southern Iran. Cancer 1971; 27:965-77.
5 Kmet J and Mahboubi E. Esophageal cancer in the Caspian littoral of Iran: Initial Studies. Science 1972; 175:846-53.
6 Mmahboubi E, Kmet J, Cook PJ, et al. Esophageal cancer studies in the Caspian littoral of Iran: The Caspian Cancer Registry. Br J Cancer 1973; 28:192-214.