International Cancer Differences
Nearly every cancer type is rarely seen in the world. The most common cancers seen in Europe (lung, breast, intestinal and prostate cancer) are very rare in sub-Saharan Africa. On the contrary, liver cancer is very common in developing countries, but rarely in Western countries.
There are two pieces of evidence showing that this international diversity is mainly caused by differences in people, lifestyle and environment.
Immigrants tend to get the cancer rates of the countries they start to live quickly. For example, low rates of breast cancer in Japanese domestic women; The risk for those who are transported to the United States, where breast cancer is prevalent, doubles. The risk of breast cancer is the same for both locals and migrants in a few generations.
Cancer rates can change rapidly in a single country. Worldwide lung cancer rates have increased tenfold in the twentieth century as cigarette smoking increases, but today again less when more people start giveup smoking.
Can these trends be explained by genes?
Genetic alterations may not account for such large increases in the cancer rate seen in only a few generations.
Only twelve chicks have the same kind of cancer when they have the same twins. This suggests that hereditary genes have a relatively small effect on cancer risk in the population.