The number of new cases of breast cancer has jumped dramatically worldwide, from about 640,000 in 1980 to more than 1.6 million in 2010, University of Washington researchers report.
Over the same period, the number of cases of cervical cancer has crept up much more slowly and deaths from that cancer have declined, although in 2010 it still killed 200,000 women around the world. In 2010, 51% of new cases of breast cancer and 76% of the 454,000 cases of cervical cancer were in developing countries, the researchers noted.
"The world used to think of breast cancer as a problem that only high-income countries had and cervical cancer as a problem mainly for developing countries," said coauthor Dr Rafael Lozano, a professor of global health at the university's Institute for Health Metrics and Evaluation.
"What we have found is that while countries such as the United States and United Kingdom have been able to greatly lower the risk of women dying from breast cancer, through better screening and treatment, countries with fewer resources are seeing their risks go up," he said.
Breast cancer cases doubling in developing countries
The world rightly recognises that no woman should die because of complications related to pregnancy and childbirth, Lozano said. "Now that we can clearly see the trends in breast and cervical cancer, they need to become a central part of the discussion when priorities are being set for women's health programmes," he said.
The report was published in The Lancet.
For the study, Lozano and colleagues collected data from more than 300 cancer registries and cause-of-death offices in 187 countries. During the 30 years covered by the study, breast cancer cases have increased in all parts of the world by 3.1% a year, the researchers found.
In addition, among women aged 15 to 49 there were twice as many cases of breast cancer in developing countries than in developed countries, they note. Deaths from breast cancer were also higher in developing countries compared with developed countries.
However, around the world the increase in deaths from breast cancer has been slower than the increases in cases. This may be due possibly to early detection and treatment advances in developed countries, the researchers say.
"It is clear from the data that since the late 1980s, women who develop breast cancer have had a better chance of surviving because early screening is working and treatment is working," Lozano said.
1 in 35 women at risk in Zimbabwe
In 1980, one out of every 32 women in the United States risked dying from breast cancer. By 2010, one out of every 46 women had that risk, he added.
When one looks at countries where screening and treatment are not as widely available, the trend is in the opposite direction, Lozano said.
"In Zimbabwe, for example, the risk has gone from one in 64 women dying to one in 35. Not only is the threat of breast cancer and cervical cancer shifting more heavily toward developing countries, it also is shifting to women of reproductive age," he said.
It used to be that these cancers were predominately a problem for women over 50, but more and more women in sub-Saharan Africa, the Middle East and South Asia are being hit by these cancers between the ages of 15 and 49, Lozano said. "In Bangladesh, more than 60 percent of women dying from breast cancer are under age 50," he added.
Since 1980, new cases and deaths from cervical cancer have increased mainly in south and east Asia, Latin America, and Africa, but have dropped substantially in high-income countries, particularly where widespread screening is available, Lozano's group found.
"Our concern there is that this is a disease that is almost entirely preventable through safe sex practices and early detection, yet it continues to kill" hundreds of thousands of women every year, Lozano said.
Risk factors for breast cancer
Ahmedin Jemal, vice president for surveillance research at the American Cancer Society, said the increase in breast cancer diagnosis is partly to increased awareness.
But most importantly, he said, the risk factors for breast cancer include reproductive factors such as late child bearing and late menopause. These factors increase with economic development [and so] increased in the developing world - not as much as in the developed world. But, that's the driving factor," he said.
In addition, obesity is a risk factor for breast cancer and it has been increasing around the world, Jemal said.
To reduce the incidence of breast cancer, Jemal says, more awareness of early detection and access to care is needed. Also, women should be encouraged to reduce the known risk factors for the disease, he said, such as obesity.
As far as cervical cancer is concerned, the increase in developing areas is due to lack of access to screening with Pap tests, he said. With the development of the HPV vaccine, Jemal said he hopes to see the rate of cervical cancer decline, especially since drug makers are making the vaccine available at a low price to developing areas.
For more information on breast cancer, visit the American Cancer Society.
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