The number of new cancer cases grew worldwide to 17.5 million in 2015 from 13.1 million in 2005. And the fastest growth is in some of the world's poorest countries, according to a report on the global burden of cancer in the Dec. 3 journal JAMA Oncology.
"Cancer is increasingly important in countries where the main disease burden has always been infectious diseases," says Dr. Christina Fitzmaurice, an author of the report and assistant professor at the Institute for Health Metrics and Evaluation and the Division of Hematology at the University of Washington in Seattle.
That's an unfortunate consequence of public health success in reducing childhood deaths and controlling diseases like tuberculosis and AIDS. People in poor countries are living longer — long enough to get cancer.
One cancer that is common in poor countries — and not so common in wealthier countries — is liver cancer. We asked Fitzmaurice about liver cancer and two other top killers.
Liver cancer is now the most common cancer in men in 11 developing nations. Why?
There are several causes, so the risks vary in different countries. They include infection with hepatitis B or hepatitis C, alcoholism, and, in some countries in sub-Saharan Africa and China, aflatoxin, which is a toxin produced by mold that can grow on rice or corn that's stored inappropriately. In Mongolia, which traditionally has a very high rate of liver cancer, there are many cases of both hepatitis B and C as well as high rates of alcoholism. Thailand also has a high rate of liver cancer, but it's a less common type caused by exposure to liver fluke, a parasite found in fresh water. Eating raw fish is primarily the way people are exposed.
How can liver cancer be prevented?
The reduction in the harmful use of alcohol is always important. And we know that vaccinating children against hepatitis B is very effective. In sub-Saharan Africa, we can prevent mother-to-child transmission by vaccinating the child soon after birth, but that can be hard because a lot of births happen at home. Using sterile medical equipment, safe blood products and not reusing needles can prevent transmission of hep B and C. Harm reduction programs, like needle exchange for addicts, can reduce transmission of hep C. And now we have highly effective hepatitis C treatment, but it's very expensive. These are global health strategies recommended by the World Health Organization.
Prevention is crucial. Even in wealthy countries like the U.S., liver cancer has low survival rates. It's just a bad disease.
Cervical cancer is another growing problem in the developing world, where 1 in 24 women develop the disease, compared to only 1 in 115 women in wealthy countries. But it is highly preventable, right?
Yes, for cervical cancer prevention is easy. HPV [human papillomavirus] infection is necessary for cervical cancer, so HPV vaccination is very effective. You can vaccinate children and young girls and that will protect them when they get older. Actually I should not say it is easy because of the difficulties countries may have accessing the vaccine, distributing it, getting people to get their children vaccinated. Easy in theory, hard in practice.
Women who have not been vaccinated and have already been exposed to HPV need to be screened for precancerous lesions, which can be removed at the time of screening. Because women are screened and treated at the same time, it can work in poor countries.
Stomach cancer is a growing problem in the developing world. How can it be prevented?
Stomach cancer is more difficult. Helicobacter pylori bacteria causes about 78 percent of stomach cancer, and antibiotic treatment of the bacteria can reduce the incidence of the disease. But few countries are screening patients for the bacteria. There are also nutritional risk factors like nitrites in foods or preserving foods in salt like they do in some Asian countries. And eating fruits and vegetables can help protect against stomach cancer.
Are some countries taking meaningful steps to prevent these cancers?
Thailand has taken steps to control liver flukes in the water and to educate people about the dangers of eating raw [or undercooked] fish. Some low-income countries have made efforts to teach farmers different methods of storing grain (to avoid the toxic mold aflatoxin.) Egypt has health policies to reduce the spread of hepatitis C and to ensure treatment through a network of regional hepatitis clinics. Rwanda offers HPV vaccine programs and has designated four hospitals as cancer centers.
What are the obstacles in carrying out preventive efforts in poor countries?
To start with, many countries don't have a comprehensive plan to control cancer. To develop a cancer control plan, you need data, and that's where this study comes in. The next big issue is that other diseases, like HIV, malaria, tuberculosis, are more pressing, and resources are limited. In many countries where we saw an increase in cancers, the complex healthcare infrastructure needed to deal with cancer is just not existent. There is a very real global cancer divide.