A “war on cancer” was declared when then President Richard Nixon signed the National Cancer Act of 1971, which sought to eradicate cancer as a major cause of death. Nearly 40 years later, approximately 560,000 Americans still die from cancer each year. However, a recent report from the American Cancer Society (ACS) and several government agencies reveals that cancer control efforts initiated over the past two decades are having some success, resulting in a significant decline in the rate of new cases of the four most common cancers, as well as in the rate of people dying from them.
Annual Report to the Nation on the Status of Cancer, 1975-2006, Featuring Trends in Colorectal Cancer
Each year since 1998, the National Cancer Institute, the ACS, the Centers for Disease Control and Prevention, and the North American Association of Central Cancer Registries provide an annual update on cancer occurrence in the United States. The 2009 report, titled the “Annual Report to the Nation on the Status of Cancer, 1975-2006, Featuring Trends in Colorectal Cancer,” includes a special feature on colorectal cancer, specifically looking at how developments in screening, prevention, and treatment may impact the number of people being diagnosed with and dying from the disease in the future.
In general, the report, which was published in the December 2009 issue of Cancer [PubMed Abstract], notes that the rate of both cancer diagnoses and deaths from all cancers combined continued to decline significantly in the US. This is true for both men and women, and for most racial and ethnic groups. Overall cancer rates continue to be higher for men than for women, but the report notes that men experienced larger declines in both incidence (defined as the number of new cases) and mortality (death) rates.
From 1999 to 2006, the rate of new cases of cancer decreased an average of nearly 1 percent per year in the US. (The rate of new cancer cases increased from 1975 through 1992, and was stable from 1992 through 1999.) The death rate from all cancers combined from 1991 to 2006 declined about 20 percent for men and 12 percent for women.
Rate of Common Cancers in Decline
In large part, this significant decline in the rate of new cases and deaths is the result of reductions in the rates of the three most common cancers in men (lung, prostate, and colorectal), and two of the three leading cancers in women (breast and colorectal).
The rate of new cases of prostate cancer decreased by 2.4 percent each year from 2000 through 2006, with 4.1 percent fewer deaths. The average annual incidence of new breast cancer diagnoses showed a 2 percent decline, with a 1.9 percent decrease in its death rate. The rate of new colorectal cancer diagnoses was down an average of 2.5 percent a year, with the rate of deaths from the disease declining 3.4 percent. And for lung cancer, the rate of new cases declined 0.8 percent a year, with the rate of deaths from the disease down 1 percent.
For men, the rate of new cases also decreased for cancers of the oral cavity, brain and nervous system, and stomach. Incidence rates were stable for cancers of the bladder and pancreas, as well as for non-Hodgkin lymphoma. The rate of new cases of myeloma, leukemia, melanoma, and cancers of the liver, kidney, and esophagus increased.
For women, the rate of new cases also decreased for cancers of the uterus, ovary, cervix, and oral cavity. Incidence rates increased for non-Hodgkin lymphoma, melanoma, leukemia, as well as for cancers of the bladder, kidney, thyroid, pancreas, and lung.
Lung Cancer — Unequal Results
More people — both men and women — die from lung cancer than any other cancer. The report notes that the rate of lung cancer deaths declined 2 percent for men as a direct result of a decline in the number of men smoking. The rate of women dying from the disease remains relatively unchanged because, as experts explain, reductions in smoking among American women, unlike American men, are relatively recent.
Special Feature on Colorectal Cancer
This year's report focuses on colorectal cancer, the second leading cause of cancer death for American men and women. Death rates dropped 3.9 percent for men and 3.4 percent for women.
Ann Zauber is a biostatistician at Memorial Sloan Kettering Cancer whose work helped to shape the report's results. According to Dr. Zauber, the report spotlights the role of statistical tools known as population-based microsimulation modeling to inform health policy. For this report, microsimulation models were used to assess the relative impact of different cancer control interventions. “This form of statistical modeling provided a quantitative assessment of the impact of changes in risk factors, increases in screening, and improved treatment on the decline in colorectal cancer deaths during the years 1975 to 2000,” she says.
The modeling estimated that increases in screening accounted for more than 50 percent of the changes observed in colorectal cancer deaths in the past. “In addition,” Dr. Zauber notes, “microsimulation modeling served as a tool to suggest that further investment in the present to increase colorectal screening would provide additional decreases in colorectal cancer deaths by 2020.” (For colorectal cancer, the recommended screening method is colonoscopy, a screening procedure capable of removing premalignant lesions and polyps before cancer develops.)
While the special feature points to significant declines in incidence rates of colorectal cancer from 1998 to 2006, it notes a troubling counter-trend in people aged 50 and younger, for whom the rate of new cases is increasing.
In general, the report's authors are encouraged by the overall decline in both cancer incidence and mortality rates for all cancers combined, attributable to gains in the most common cancers. They stress, however, that further work needs to be done in the areas of prevention, screening, and treatment to reduce the rate of new cases and deaths from the many other cancers that have not experienced declines.