News and CommentTHE WAR ON CANCER

Cancer Warriors Claim a Victory

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Science  20 Mar 1998:
Vol. 279, Issue 5358, pp. 1842-1843
DOI: 10.1126/science.279.5358.1842b

The news couldn't have come at a better time for cancer researchers: Just as Congress began working on the 1999 biomedical budget, a group of experts announced last week that the United States has “turned the corner in the war on cancer.” That was the word from David Rosenthal, president of the American Cancer Society, as he and other public health leaders released encouraging data at a press conference in Washington, D.C. According to their report (published in the 15 March issue of Cancer), a sea change occurred in 1992. In that year, cancer rates that had been rising steadily from the 1930s through the 1980s reversed and began to drift downward.

The average death rate for all types of cancer, which had been rising at 0.4% per year from 1973 to 1990, dropped 0.5% per year from 1990 to 1995. At the same time, the incidence of new cases (based on a sample of 9.5% of the population) began to recede. After climbing at an annual rate of 1.2% from 1973 to 1990, cancer incidence has been declining by 0.7% annually in recent years.

Turning point.

New cancer cases (left) and deaths began to decline in 1992.

SOURCE: NCI, BASED ON SEER/NCHS/CENSUS DATA

Many biostatisticians—including Harry Rosenberg of the National Center for Health Statistics in Hyattsville, Maryland, a co-author of the report—agree that one cancer is driving these overall trends: lung cancer. Aided by a long-term decline in stomach cancer deaths and more recent declines in deaths from breast and colorectal cancer, the decline in smoking has helped push down average cancer death rates. People began to give up cigarettes after the surgeon general branded them a cancer risk in 1964. The effects of that shift in behavior showed up first in lung cancer rates among men, which have been declining since 1984. For women, who started smoking later, lung cancer incidence is still climbing, although its rate of increase has slowed since 1994. Another factor in the decline in mortality rates for some cancers is the widespread use of improved detection methods, such as mammography, that can catch cancers early.

The importance of smoking trends and early detection means, says John Bailar, a biostatistician at the University of Chicago, that “the government has had little role” in directing the recent improvements, which reflect decisions by millions of individuals to improve their lifestyle. Basic research may have resulted in an explosion of new knowledge about the molecular processes that lead to cancer, but these findings have had little impact on overall cancer figures, Bailar and others argue.

National Cancer Institute (NCI) director Richard Klausner says, however, that the data “do not reveal the real improvements in the quality of life for cancer survivors” made possible by improvements in therapy and medical care. It is very difficult, Klausner argues, to ascribe causes to any changes in cancer rates—other than to those related to tobacco. But “we know that for certain cancers, screening and therapy have made a difference” in prolonging life, he says. For example, he points out that clinical trials have established that surgery plus adjuvant therapy—including tamoxifen, which is designed to block cancer in a second breast, and mixed drug cocktails known as “polychemotherapy”—have reduced deaths from breast cancer. As for contributions from basic research, Klausner predicts that NCI-supported studies of cancer genetics should pay off in the future with improved diagnostics and screening—and, before long, in new methods of targeting chemotherapeutic agents more effectively. But at the moment, he concedes, “this is a hypothesis.”

Klausner also cautions that although many trends in the “cancer report card,” as the authors called it, are favorable, there's no cause for complacency. The incidence of cancer of the skin and lymph system, for example, continues to increase, and African Americans have not shared in the improvements seen in the Caucasian population—partly because blacks may have poorer access to screening and therapy. Blacks were specifically at greater risk for developing and dying of breast and prostate cancer.

For whites, one of the most dangerous cancers is melanoma, whose incidence is rising at a rate of about 2.5% a year. Despite its lethality, however, melanoma is often manageable if caught early; deaths have been declining at 0.4% a year since 1990, reversing a previous upward trend. But the battle against the lymph disease known as non-Hodgkin's lymphoma has not been going so well. Incidence rose at 3.5% a year in the 1980s; while it slowed after 1990, it continued to climb at a rate of 0.8% per year. It remains lethal: For unknown reasons, the death rate from this cancer actually increased faster—by 1.9% per year—in the 1990s than it did in the 1980s.

The most likely explanation for the rise in skin cancer, says Brenda Edwards, an NCI statistician and co-author of this report, is that “we have a lot more leisure time to spend at the beach and on the tennis courts,” where people get sunburned. There is no consensus on why non-Hodgkin's lymphoma is climbing among older people, says NCI researcher Lynn Ries, adding that “studies are under way.” Also targeted for investigation, says Edwards, is a rise in brain cancer among the elderly

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