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Less smoking, earlier detection, and improved treatments are credited for gains against lung, colon, prostate, and breast cancer
The latest federal cancer numbers, released on Dec. 7, show a modest but steady decline in the U.S. over six years for both deaths from the disease and new diagnoses. The improvement is driven largely by declines in the big four cancer killers—lung, colon, prostate, and breast. Specialists attributed the declines to a reduction in the smoking rate, better and earlier detection, and improved treatments, particularly those that can be matched to a patient's specific tumor type. New diagnoses for all types of cancer decreased almost 1% per year on average from 1999 to 2006, while cancer deaths decreased 1.6% per year from 2001 to 2006. However, experts in the field warn that these successes could be wiped out in coming years by the nation's obesity crisis. Because fat cells fuel tumor growth, about one-third of cancer cases today can be linked to obesity. "The increase in obesity is a real concern and could eventually cause this very welcome decline to reverse," says Dr. Edward J. Benz, president of Dana-Farber Cancer Institute in Boston. "We don't know yet but it is quite possible that obesity will become as much or more of a factor in causing cancer than smoking." Cancer is currently the nation's second-largest killer after heart disease. An estimated 562,340 people in the U.S. will die from the disease this year, accounting for nearly 1 in 4 deaths. The six-year declines—reported by the National Cancer Institute, the Centers for Disease Control & Prevention, the American Cancer Society, and the North American Association of Central Cancer Registries, or NAACCR—are far from a home run. The annual federal cancer report had shown small declines in the death rate in each of the past five years, but this is only the second year that a decline in diagnoses was recorded (after 2008). And both drops were considered "significant" in the cancer world, where anything more than a 1% decline is something to celebrate when placed against such a formidable disease. The persistence of the declines gives cancer specialists encouragement that steady progress is finally being made in treatment, screening, and prevention, after decades when the trend lines barely budged. "We still have a long, long way to go but I am optimistic," says Dr. Raymond DuBois, provost of M.D. Anderson Cancer Center in Houston. "If these trends continue for another few years, we will be certain that the progress is real." Under-50 Mammograms
Even though early detection was considered a key factor in the declines, specialists said the findings did not undercut the recommendation on Nov. 16 by the U.S. Preventive Services Task Force that annual mammograms are not needed until age 50 for women who are at low risk for breast cancer. "These new statistics weren't broken down by age," says Benz. "Although I think that early detection by mammograms does contribute to these improvements, whether the results are due to screening starting at age 40 or age 50 cannot be determined." The task force based its recommendation on an analysis that found that almost 2,000 mammograms would have to be performed on women ages 40 to 49 over 10 years to prevent one breast-cancer death. All those mammograms do pick up a high number of false positives, however, with resulting unnecessary follow-up procedures such as biopsies that can be stressful, costly, and sometimes harmful. That raises concerns that mass screening of younger women is doing more harm than good. Overall, the new report found that cancer rates were higher for men than for women, but men experienced the greatest declines in new cases and death rates. For both men and women, however, there was little progress in many less common cancers, such as kidney cancer, and even some increases. Colon and rectal cancer, usually categorized together as colorectal cancer, had the biggest declines. Deaths dropped by 3.9% per year for men and 3.4% per year for women over the six-year period. Colorectal is the third-leading cause of cancer death and much of the improvement was linked to a greater adoption of colon screening, which can be very effective at not only detecting tumors but removing the polyps that could later turn cancerous. However, the researchers noted that there is an increasing incidence of colorectal cancer in men and women under age 50. Colorectal cancer has been linked in some studies to obesity and a high-fat diet. Incidence-Rate Declines
The report found that, in men, incidence rates have declined for cancers of the lung, prostate, colon/rectum, oral cavity, stomach, and brain. But incidence rates continue to rise for kidney/renal, liver, and esophageal cancer, melanoma, and blood cancers. In women, incidence rates decreased for breast, colorectal, uterine, ovarian, cervical, and oral cavity cancers, but increased for lung, thyroid, pancreatic, bladder, and kidney cancers, as well as for non-Hodgkin lymphoma, melanoma, and leukemia. "The continued decline in incidence and death rates for all cancers combined is extremely encouraging, but progress has been more limited for certain types of cancer, including many cancers that are currently less amenable to screening, such as cancer of the esophagus, liver, and pancreas," said Betsy Kohler, executive director of NAACCR. The three leading causes of cancer death for all men, with the exception of Asians/Pacific Islanders, were lung, prostate, and colorectal cancer. Lung, liver, and colorectal cancers were the top three causes of cancer death in Asian/Pacific Islander men. For women, the three leading causes of cancer death were lung, breast, and colorectal cancer for all racial/ethnic groups except Hispanic women, for whom breast cancer ranked first. The report was published online on Dec. 7 in the journal Cancer. To view the full report, go to www.interscience.wiley.com/cancer/report2009.