Diagnostics & Imaging Week Washington Editor
BETHESDA, Maryland – The National Cancer Institute (NCI; Bethesda, Maryland) released a report on cancer for 2006 and while the numbers for some cancer fatalities seem to trend down, the numbers offer several anomalies that researchers have yet to decipher.
Brenda Edwards, PhD, associate director of the surveillance research program at NCI, gave an overview of the statistics compiled for the 2006 edition of the Report to the Nation, and one of the more interesting findings was that men and women of Latino/Hispanic extraction continue to exhibit lower rates of cancer than African-Americans or non-Latino whites despite some Census Bureau data that would seem to indicate otherwise.
Edwards stated that the cancer numbers for 2003 cover more than 90% of the U.S. population, thanks to the greater number of states with cancer registries. In 1975, the existing base of registries provided the Institute with data on only about 10% of the population. At that time, the vast majority of states had no registries whereas in 2003, only six states reported no cancer statistics.
The numbers in Edwards' presentation indicated that NCI expects that roughly 1.4 million Americans will have been diagnosed with one form of cancer or another in 2006, a number provided by the American Cancer Society (Atlanta).
"We think that this estimate is a little low," due to underreporting, Edwards said. She noted that there is "a small but steady increase" in the overall incidence of cancer in women, driven in part by an increase in lung cancer. Conversely, lung cancer is falling in men.
"Certainly tobacco use is implicated" in the increase in women's lung cancer, Edwards said, adding, not surprisingly, that the drop in men's lung cancer is due primarily to decreases in smoking. Incidence rates of cancers that are trending downward include those of the ovaries, cervix and colorectal tissues.
Prostate cancer will top all cancer diagnoses for 2006 estimates at more than 234,000, and breast cancer is expected to generate just under 213,000. Lung cancer should show up as a diagnosis approximately in 175,000, and the sole remaining category at more than 100,000 is expected to be for colorectal cancers at almost 149,000.
The deadliest cancer, both absolutely and relative to diagnosis, is lung cancer, expected to claim the lives of more than 162,000 men and women in the U.S. this year — more than 92% of diagnoses. If the overall numbers for breast cancer hold, almost 41,000 women will lose their lives for a rate of 45% (fatalities include those diagnosed in previous years).
Breast cancer and pancreatic cancer diagnoses seem to have stabilized, according to Edwards, but the fate of various demographic groups do not follow the overall numbers precisely. Between 2000 and 2003, the overall U.S. incidence of breast cancer was roughly 129 per 100,000, but the per-100,000 rates for white, non-Latina women topped all racial/ethnic groups at 134 and those for Latina women came in at 89.1. African American women fell between the two at 118.
The lowest incidence of breast cancer diagnosis was found in women in the American Indian/Alaskan native group at 74.4 per 100,000.
The overall age-adjusted death rates from breast cancer tracked the incidence numbers in some cases, but mortality numbers for at least one demographic ran counter. African American women exhibited by far the greatest mortality rates at 34.3 per 100,000 women followed by non-Latina whites at 25.8. Latina women exhibited a mortality rate of just over 16 per 100,000, and women of Asian and Pacific Island origin succumbed to breast cancer at a rate of 12.6 per 100,000.
Recent breast cancer rates of incidence have trended downward slightly according to Edward's chart, but that drop is based on two data points, which she said were not enough to be deemed statistically significant.
Edwards said that the apparent drop in breast cancer incidence seems to track the publication of the report on hormone therapy from the Women's Health Initiative study that depicted a greater incidence of heart disease and breast cancer in women who were on long-term treatment with combination hormone therapies.
In a discussion of cancer rates among Latinos, Barry Miller, an epidemiologist at the surveillance research program at NCI, said that the numbers for this group did not include national origins. About 58% of this group hailed from Mexico, 6% from Cuba and the Dominican Republic, and the balance from other nations in Central and South America, he said.
"Latinos have lower rates for many cancers that are common in affluent, industrialized countries," Miller noted in a reference to lung, colorectal, breast and prostate cancers, but also demonstrated "a higher incidence . . . associated with infectious agents," including cancers of the stomach, liver and cervix.
Miller was at a loss as to how Latino men and women exhibit a lower overall incidence of cancer despite socio-economic indicators that would seem to suggest the reverse. He stated that the Census Bureau's 2000 survey indicated that only 52% of Americans of Hispanic ancestry had completed high school in contrast to 72% of African -Americans and almost 86% of non-Latino whites.
On the other hand, the poverty level for Latinos is below that of African-Americans, 22.6% to 24.8% (the rate for non-Latino whites was 8.1%).
Access to healthcare skewed away from Latinos, with more than 35% of those under the age of 65 possessing no healthcare coverage (18.6% black, 12% non-Latino white). Medicare-eligible population numbers were much closer, with 5.3% of Latinos going without coverage (African-American 2%, non-Latino white 0.6%).
Lifestyle risks seemed to offer only some help in explaining the lower incidence of cancers in this group. According to numbers provided by the National Health Interview Survey of 2003 (published by the Centers for Disease Control and Prevention), Latino men are less likely to smoke than the other two groups by several percentage points (21.2%, 25.4%, 24.6%), and Latino women are far less likely to smoke (10.3%, 18.3%, 22.1%).
Obesity numbers do little to clarify the picture. Latino men and African-American men demonstrated identical rates of obesity at 27.8% and non-Latino whites 28%, but the numbers for women varied sharply. Latino women who were obese in the 2000 Census made up 38% of their overall numbers, a sharp drop from African-American women at almost 49% and non-Latina whites at 30.7%.