Most Cancer Rates Down, Study Finds
Cancer incidence and death rates dropped steadily in the United States in the 1990s, but new cases of breast cancer increased, according to a report released Tuesday.
The new figures, part of an annual survey compiled by several agencies, extend a years-long downturn in overall cancer incidence that began in 1992, following decades of increases.
Although death rates from breast cancer continued to decline, the incidence of the disease climbed 1.2% annually from 1992 to 1998, part of an overall rise of 40% since 1973. So far, a precise cause has eluded researchers.
“There are several possible reasons, but no one is sure which are important,” said Dr. Michael Thun, an epidemiologist at the American Cancer Society and one of the report’s authors.
Early detection with mammography is part of the explanation, experts said, but the possible role of other factors is still unclear, among them the use of hormones after menopause, delayed childbearing, post-menopausal obesity and younger onset of menstruation.
The findings were contained in an annual report to the nation on cancer, a collaboration of the cancer society, the National Cancer Institute, the Centers for Disease Control and Prevention and the North American Assn. of Central Cancer Registries. Published in today’s issue of the Journal of the National Cancer Institute, the findings contain data through 1998, the most recent year for which information is available. Both the death rates and incidence rates were measured as the number per 100,000 people.
Most encouraging, overall cancer incidence declined by an average of 1.1% annually from 1992 to 1998, and death rates dropped 1.4% annually from 1994 to 1998. The largest decreases in deaths occurred among men, especially among black men, who bear the heaviest cancer burden.
About 552,000 Americans are expected to die of cancer this year, and 1.2 million new cases will be diagnosed. It is among the diseases Americans fear the most, although heart disease is the nation’s leading killer.
The overall drop in new cases of cancer, which began in 1992 and was first reported six years later, marked a stunning reversal of decades of escalating rates.
Officials Credit Healthier Lifestyles
Death rates increased until 1991, leveled off until 1994 and have declined annually since.
Officials have attributed the steady downward trends to improved vigilance among Americans, who are benefiting from early screening and advances in treatment and are smoking less, improving their diets and exercising more.
The single biggest factor responsible for the trends is Americans’ increasing abandonment of tobacco.
This has been especially striking among African American men and accounts for their decreasing cancer mortality, the report found. In 1965, 60.4% of African American men smoked; by 1998, the number had decreased to 29%. Tobacco use is responsible for nearly 30% of all cancer deaths.
Lung cancer death rates for men began to decrease in 1990 and dropped 1.9% annually from 1992 to 1998.
Lung cancer deaths among women are still rising, however, the result of their having started smoking--and quitting--later than men.
Lung cancer deaths among women increased 0.8% each year from 1992 to 1998, although there has been a gradual slowing in their death rates over the last 30 years, the report said.
After long-term increases, female lung cancer cases have leveled off since 1991.
Overall, lung cancer cases have decreased 1.6% annually from 1992 to 1998.
About a dozen cancers continue to rise in incidence or mortality, including breast and female lung cancer and such diverse and uncommon cancers as melanoma, non-Hodgkin’s lymphoma, thyroid and esophageal.
Breast cancer is the most commonly occurring cancer among women, with 192,200 new cases this year and 40,200 deaths among women diagnosed earlier.
Researchers said that more early-stage breast cancer is being diagnosed, which suggests that more aggressive screening and early detection, primarily through mammography, may account for part of the increase.
“We still just don’t know what is really causing this disease,” said Susan Braun, president of the Susan G. Komen Breast Cancer Foundation. “The fortunate thing is that we are also seeing a trend toward earlier diagnosis.”
She noted that the nation is likely to see even greater increases in the coming years as the population ages, since breast cancer is largely a disease of older women.
“We are going to be facing more and more cases of breast cancer each year,” she said. “We are really recognizing that we have to rev up for that.”
Prostate cancer began to increase sharply starting in the late 1980s, a result of the introduction of prostate specific antigen (or PSA) screening, but incidence and death rates have begun to decline, officials said.
Numbers Vary Across Country
Prostate cancer incidence rates fluctuate around the country depending on the use of the PSA test, the report said. Geographic areas of high usage report high incidence rates, although these often result in the discovery of “clinically insignificant” tumors, the report said.
“We need tools to distinguish aggressive tumors from nonaggressive ones,” Thun said. “If we knew which were bad actors, we could reserve the more radical treatments for those and reduce unnecessary treatments.”
In colorectal cancer, incidence rates for white men declined 1.3% per year during the 1992-98 time frame and remained stable for black males and black and white females.
Long-term tends show that incidence rates overall increased until 1985, decreased 1.8% annually through 1995, then stabilized through 1998. Death rates decreased overall from 1992-98, except for black females, where rates remain stable.
Cancer Rates
Annual percentage change from 1992 to 1998:
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New cases Deaths All Cancers -1.1 -1.1 Male -2.7 -1.6 Female 0.3 -0.8 Breast 1.2 -2.4 Prostate -5.1 -3.5 Lung -1.6 -0.8 Colorectum -0.7 -1.8 Non-Hodgkin’s Lymphoma 0.1 1.1 Melanoma 2.8 0.4
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Source: Journal of the National Cancer Institute
Cancer Rates
