Cancer death rates declining but obesity still needs to be tackled

By Dr. Ananya Mandal, MDMar 29 2012

According to a new report from four major national cancer tracking groups there has been a steady decline in cancer death rates for men, women and children from 2004 to 2008. The declines in death and new cases of cancer reflect progress against the disease in terms of prevention, diagnosis and treatment, but experts say rising obesity may present a new challenge in the fight against cancer.

From 1999 to 2008, cancer death rates declined by an average of 1.7 percent per year for men, 1.3 percent per year for women and 1.5 percent annually for children, according to the report from the U.S. Centers for Disease Control and Prevention, the American Cancer Society, the National Cancer Institute and the North American Association of Central Cancer Registries. The report was published online in the journal Cancer.

The declining death rates applied to all types of cancer, including the four most common: lung, colorectal, breast and prostate cancers. The numbers of new cases of many cancers have also been on the decline. New cases of many specific cancers went down, including prostate, colorectal, lung and breast cancers. But certain kinds of cancer actually increased, such as those of the pancreas, kidney, thyroid, liver and melanoma. Cancer of all types among men dropped by 0.6 percent each year from 2004 to 2008, the report said. Among women, the rate of new cases declined by 0.5 percent each year from 1998 to 2006, then leveled off until 2008.

This decline in cancer deaths began since the 1990s. Experts say the declines in both deaths and new cases of cancer are the result of a general better scientific understanding of how to diagnose, treat and prevent cancer. “The declines we've been seeing now, this reflects a lot of what we knew and applied and advances in the delivery of care that has been going on for a while,” said Brenda Edwards, a senior advisor for surveillance at the National Cancer Institute.

“We know much more in terms of cancer prevention, particularly with regard to smoking,” said Ahmedin Jemal, vice president for surveillance research at the American Cancer Society. “Quitting smoking substantially reduces the risk of developing cancers related to smoking. But there are still many people who smoke.” The CDC reports that in 2010, 43.5 million Americans were current smokers, a number that has remained fairly steady since 2005.

The new report focused on the number of Americans who are overweight or obese, a factor that could undo some of the recent advances. The report noted that certain kinds of cancer that have been increasing, such as pancreatic and kidney cancers and adenocarcinoma of the esophagus are associated with excess body weight. Some studies have estimated that as much as 40 percent of certain kinds of cancer, such as endometrial cancer or esophageal adenocarcinoma, can be attributed to obesity.

Dr. Rachel Ballard-Barbash, associate director of the Applied Research Program at NCI, said the report doesn't specifically tie rises in these cancers with the growing numbers of overweight and obese Americans, but that it's possible the two are connected. “We could have some sense of optimism from looking at what has happened to lung cancer rates. As population smoking declined, that led to marked reductions in lung cancer incidence and mortality,” she said. “For people who do not smoke, what one does on a daily basis in terms of diet and physical activity is something you can control the most in terms of your cancer risk.”

“Cancer is becoming a chronic disease because we can treat people better now and they can live longer…But we are beginning to see the effect of health behaviors on the outcomes for cancer survivors. There are things you can do to improve prognosis and quality of life, such as losing weight, improving nutrition and exercising. It is similar to what we learned about heart disease.”

Obesity and insulin resistance may be a high-risk state for disease progression among cancer survivors Ballard-Barbash explained.

“I don't think Americans understand the association between cancer and obesity,” said physician Marcus Plescia, director of the division of cancer prevention for the Centers for Disease Control and Prevention. “We do know people are afraid of cancer. They know about the links (from obesity) to diabetes, heart disease and arthritis, but many don't know about this. They need to know.” “Education (campaigns) about the risks associated with smoking have been successful,” said Plescia. He added that this year's report documents the second straight year of decreasing lung cancer death rates among women. “This is an important trend. We hope to spread the same important message about obesity.”

Postmenopausal breast cancer leveled off from 2005-2008 after declining from 1999-2005. The report credits the changes to discontinuation of hormone replacement therapy, a known risk factor for breast cancer. “Breast cancer incidence did drop when hormones were stopped, but it has now plateaued," said Dr. Powel Brown, chairman of clinical cancer prevention in the department of breast medical oncology at the University of Texas MD Anderson Cancer Center in Houston.