Factors associated with cancer of the oesophagus: an overview.

The incidence pattern of oesophageal cancer varies across the world with roughly a 500-fold difference in rates (truncated) between the highest and lowest areas. The incidence rate of this disease is rising in many countries, especially in males. Although ethnicity is a strong indicator of risk of this disease, no specific genetic factor except the occurrence of this cancer among the members of families with tylosis has been identified. The frequency of oesophageal cancer varies among the native and immigrant populations in different countries. Oesophageal cancer was found to be strongly associated with the consumption of alcohol and tobacco, especially in combination. A low socioeconomic level and poor diet, particularly deficiencies of vitamins A, C, and riboflavin, are other characteristics of the regions of highest incidence. Physical damage of the oesophagus caused by ingesting hard foods and/or hot liquids could be another factor. Intensive research in high-risk regions failed to reveal the presence of nitrosocompounds except at a very low level or other known carcinogens. The mutagenicity of pickled vegetables commonly consumed in the high-risk regions of China and high frequency of oesophageal cancer among chickens in the same regions suggest the existence of "common" carcinogens. It seems probable that in Iran an initiating carcinogenic factor may be the custom of eating opium dross, which has been shown to be mutagenic, as well as consumption of contaminated bread with extraneous seeds containing a large quantity of silica fibres, which is a strong stimulant of growth.