WASHINGTON—Overall incidence and mortality rates for cancer continue to decline in the United States. However, a new report finds considerable disparities among racial and ethnic groups, and it warns that a resurgence of smoking among teen-agers forewarns of a likely reversal of the downward trend, especially for lung cancer.
“In the increases in tobacco use among teens, we can also see the seeds of future increases in cancer,” said James S. Mark, MD, of the Centers for Disease Control and Prevention (CDC), who spoke at a press conference releasing the statistics.
The incidence rate for all cancers combined declined an average of 0.9% per year from 1990 to 1996, and the death rate dropped an average of 0.6% annually. The trend continues to reverse the upward climb in overall incidence and mortality documented from 1973 to 1990.
“The scourge of cancer has been so pervasive that even the relatively small decline each year—a fraction of a percent—means that now 53,000 fewer Americans get cancer each year than would have had the rates from 1990 not changed and that about 18,000 fewer die,” Dr. Marks said.
The report was prepared by the American Cancer Society (ACS), National Cancer Institute (NCI), and CDC. Incidence data came from NCI’s Surveillance, Epidemiology, and End Results (SEER) program. Mortality data came from the National Center for Health Statistics’ national database of death certificates. For the first time, the report included a breakdown of cancers among Hispanics, Asians and Pacific Islanders, and American Indians and Alaskan Natives in addition to whites and blacks.
A Combination of Reasons
The precise reason for the overall decline remains unknown, although screening, treatment, and prevention all receive some credit. “It’s undoubtedly a combination of screening and treatments primarily, but we’re trying to figure out exactly how much to attribute to each point,” said Barbara K. Rimer, DrPH, director of NCI’s Division of Cancer Control and Population Sciences.
Among the five most common-occurring cancers—breast, prostate, lung, colorectal, and non-Hodgkin’s lymphoma—only non-Hodgkin’s lymphoma showed an upward trend, with an average annual increase of 0.6% in incidence and 1.8% in deaths rates.
Although breast cancer incidence remained flat during the period, deaths declined at an annual rate of 1.8%. Incidence also dropped 2% for prostate cancer, 1.4% for lung cancer, and 2.1% for colorectal cancer. Mortality dropped 1.6% for prostate cancer, 0.4% for lung cancer, and 1.7% for colorectal cancer.
The overall decline in cancer incidence and mortality was significantly influenced by decreases in the four leading malignancies. “Breast, prostate, lung, and colon are responsible for over half of all cancers,” said National Center for Health Statistics director Edward J. Sondik, PhD.
The average annual increase in the incidence of non-Hodgkin’s lymphoma during 1990-1996 (0.6%) was significantly lower than from 1973-1979 (3%) and during the 1980s (3.7%). The average annual increase in the death rate for the disease (1.8%) was lower than during the 1980s (2.4%), but this slowing was accounted for entirely by a decline in the annual average rate for men (1.5%).
The melanoma incidence rate rose substantially from 1990 to 1996, rising an average of 2.7% per year. However, the mortality rate for melanoma remained constant. The average yearly drop of 0.3% in pancreatic cancer mortality resulted from a decline in mortality among men (0.8% a year), which offset an average annual increase among women (0.1%).
Considerable variations among different populations appeared in the mortality and incidence figures. Breast, prostate, lung, and colorectal cancer were ranked in the top four most common-occurring cancers for all the populations. “For the remainder of the top 10 sites, there were notable differences,” Dr. Sondik said.
Some sites tended to be unique to a specific population. For example, melanoma was among the top 10 only in the white population; cancer of the pancreas only in blacks; liver cancer only in Asians/Pacific Islanders and American Indians/Alaskan Natives; and bladder cancer only in whites and Hispanics.
With one exception, the same four sites were also the top four causes of cancer death, the report said. For Asian and Pacific Islanders, breast cancer was replaced in the top four by liver cancer.
“While incidence rates for blacks are about 10% higher than whites for all sites combined, mortality was more than 30% higher,” Dr. Sondik said. “African-Americans have the highest rate of new cancer cases for all the major cancers, except breast cancer, and death rates are highest among blacks for all these cancers as well.”
The report features a special section on tobacco and lung cancer, which caused 28% of cancer deaths in 1998. During the first 7 years of the 1990s, lung cancer incidence and mortality rates decreased in men and increased in women, although the rate of increase has slowed in recent years. Indeed, the report found a decrease for the first time in lung cancer incidence and death rates among women under 60.
“We must be mindful that these favorable trends are influenced most by the reduction in adult tobacco use in the past 2½ decades,” said John R. Seffrin, PhD, the ACS chief executive officer—thus the concern about teenage smoking, which increased among whites, blacks, and Hispanics from 1991 to 1997.
