Patterns of cancer in developed and developing countries

In other posts I have been talking about the differences in rankings between developed and developing countries in both incidence and mortality for cancer. The patterns vary by geography and economic status, which correlate roughly with the causes of cancer in the “environment” in its broadest sense. The majority of cancers in more developed countries are those associated with more affluent lifestyles—cancers of the lung, colon and rectum, breast, and prostate. In contrast, cancers of the liver, stomach, esophagus, and cervix—all related directly or indirectly to infectious agents—are relatively more common in developing countries. Where treatment is largely unavailable, all cancers have a poor prognosis, but in this group, all but cervical cancer have poor outcomes everywhere. The mix of common cancers varies  as seen in the following table (source: Cancer Control Opportunities in Low- and Middle-Income Countries, see website link in the list). Click to enlarge. 

 

 

In developed countries the incidence of tumors of the breast, colon, lung and corpus uteri is higher than in developing countries, with a ratio, respectively, of 1.23/1; 1.95/1; 1.02/1; and 2.19/1. The mortality of these tumors, however, is lower than in developing countries: breast 29.8% vs 42.8%; colon 49,3% vs. 60.0%; lung 82.5% vs. 86.5%, and corpus uteri 21.32% vs. 33.8%. . The higher mortality of these tumors in the developing world is caused by a delay in the diagnosis of the disease, i.e. the tumor is disclosed in a more advanced stage of progression when therapy is less effective or useless. Due to these factors at least for breast cancer and lung cancer the number of people dying of these tumors in developing countries is likely to be higher than in the developed world.

 In developing or low-income countries the incidence of tumors of the cervix uteri, stomach, liver, and esophagus is much higher than in developed countries with ratios, respectively, of 6,49/1; 1,86/1; 4,08/1, and 8,12/1. The higher incidence of these tumors is broadly explicable by differences in exposure to certain infectious agents (HPV, HBV, HIV, etc) or carcinogens (stomach and esophagus) but it is also strongly related to the lack of primary prevention (vaccination against HPV and HBV), to an ineffective secondary prevention (i.e., screening of carcinoma of cervix uteri), and to the lack of health facilities for early diagnosis and treatment. In fact, it is very frustrating to realize that in developing countries most of the people dying for cancer were suffering from preventable or somewhat curable malignancies!. It is for this reason that all efforts should be made by the global cancer community to take immediate steps to slow and ultimately reverse the phenomenon.