NCI Cancer Bulletin: A Trusted Source for Cancer Research NewsNCI Cancer Bulletin: A Trusted Source for Cancer Research News
February 20, 2007 • Volume 4 / Number 8 E-Mail This Document  |  Download PDF  |  Bulletin Archive/Search  |  Subscribe

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Cancer Research HighlightsCancer Research Highlights

Disparities Found in Colonoscopy Use by Those on Medicare

Screening rates for colorectal cancer in the United States lag far behind those for breast and cervical cancer, despite research showing that the high mortality rates could be lowered significantly by detecting colorectal cancer at an early stage when it is more treatable. A study in the February 12 Archives of Internal Medicine of nearly 600,000 Medicare recipients aged 65 or older living in Illinois, Florida, and New York shows that women, nonwhites, and people with low income or educational levels were less likely to get a colon screening test than were men, whites, and people with higher incomes and education levels.

Over a 2-year period, 18.3 percent of all men and women in the study group had a colon screening test, although women were less likely to undergo invasive screening tests such as colonoscopy. The frequency of screening by both sexes diminished with age, but more so in women.

Most (89.5 percent) beneficiaries in the study were white; blacks, Hispanics, and all other racial and ethnic groups were aggregated together as nonwhite, and were 48 percent less likely to get any screening test than were white participants. Beneficiaries living in areas with the highest proportion of high school graduates were 52 percent more likely to get screened. In general, living in a zip code with a higher per capita income increased the likelihood of getting screened, though nonwhites in the highest income group were actually less likely to be screened. Whites were more likely to get a colonoscopy as their income increased; nonwhites were not.

"Further research is needed to determine the basis for the observed ongoing disparities to develop interventions to reduce and eliminate these differences," wrote Dr. Ashwin N. Ananthakrishnan from the Medical College of Wisconsin in Milwaukee, lead researcher on the study.

Switching Hormone Therapies Reduces Mortality from Breast Cancer

Pooled results from two randomized clinical trials, published online ahead of print in Cancer, indicate that women taking tamoxifen after surgery for breast cancer who switch to an aromatase inhibitor after 2 or 3 years have improved survival compared with women who continue tamoxifen for an additional 2 or 3 years.

The investigators combined the results from the GROCTA 4B trial, which tested the aromatase inhibitor aminoglutethimide, and the ITA trial, which tested the aromatase inhibitor anastrozole (Arimidex). Combination of the data was planned into the design of the ITA trial, which was performed by the same collaborative group as GROCTA 4B.

In GROCTA 4B, investigators randomly assigned women who had already been taking tamoxifen for an average of 3 years to either continue taking tamoxifen at the same dose for an additional 2 years or to switch to aminoglutethimide for an equivalent period of time. The design of ITA mirrored that of GROCTA 4B, except that women assigned to switch drugs were given anastrozole.

In the combined analysis, all-cause mortality and breast cancer-related mortality were both significantly improved in women who switched to one of the aromatase inhibitors. Although the trials had several limitations, including the fact that neither trial reached its recruitment goal, the results mirror those of other recently published studies, explained the authors. "The present data and mortality benefits emerging from the most recent reports of the other switching trials…reinforce the indication of early switching to an aromatase inhibitor in women presently receiving adjuvant treatment with tamoxifen," they wrote.

Lung Cancer Incidence Rates High Among Women Who Have Never Smoked

While smoking remains the predominant cause of lung cancer, a new study reveals that incidence rates of lung cancer among people who have never smoked (never smokers) are higher in women than in men. The study results were published in the February 10 Journal of Clinical Oncology. This study is unlike previous studies that focused mainly on mortality rates and that found men had higher lung cancer mortality rates than women.

Dr. Heather A. Wakelee of the Stanford Comprehensive Cancer Center and colleagues calculated the incidence of lung cancer among never smokers, former smokers, and smokers aged 40 to 79 from six large cohort populations: the Nurses' Health Study, the Health Professionals Follow-Up Study, the California Teachers Study, the Multiethnic Cohort Study, the First National Health and Nutrition Examination Survey Epidemiologic Follow-Up Study, and the Swedish Lung Cancer Register in the Uppsala/Orebro region. Lung cancer incidence was calculated as new cases per person-year.

Lung cancer incidence rates among female never smokers aged 40 to 79 ranged from 14.4 to 20.8 per 100,000 person-years, while incidence rates among male never smokers aged 40 to 79 ranged from 4.8 to 13.7 per 100,000 person-years.

While researchers have not pinpointed the underlying cause of the greater incidence of lung cancer in female never smokers, they have identified the following as potential risk factors: secondhand smoke; occupational exposures such as asbestos, chromium, or arsenic; environmental exposures such as domestic radon; indoor pollutants; previous lung disease; dietary factors; family history; and genetic factors.

Dr. Adi F. Gazdar of the University of Texas Southwestern Medical Center in Dallas and Dr. Michael J. Thun of the American Cancer Society wrote in an accompanying editorial, "Clearly, lack of an understanding of the factors responsible for lung cancers in never smokers is a major deficiency that must be addressed before we can explore preventive strategies." Also, the differences the investigators found in the histological types of lung cancer, as well as the genetic differences between nonsmokers and smokers, could have implications for improving treatments and outcomes of lung cancer.

Gene Involved in Brain Development Has Role in Tumors

A gene that helps control the growth of stem cells during brain development also plays a role in regulating the growth of malignant glioma, a deadly brain cancer, according to a new study. The gene, Olig2 (oligodendrocyte lineage transcription factor 2), produces a protein found only in the nervous system that controls the activity of other genes. Experiments in mice suggest that this protein could be a potential target of therapies that are specific to the nervous system.

Drs. Charles Stiles and David Rowitch of the Dana-Farber Cancer Institute led the study, which appeared in the February 15 Neuron. Using tumor tissue from patients with glioma, the researchers found that the Olig2 protein was expressed in two types of cells - cancer stem cells and progenitor cells - that contribute to the growth of glioma. Further experiments in mice indicated that the protein helps regulate a cellular process, or pathway, involved in tumor growth.

Together with previous research, the new findings suggest that Olig2 controls a critical pathway involved in the proliferation of normal and malignant stem cells in the central nervous system. The results also highlight the benefits of stem cell research in understanding human cancers, says lead author Dr. Keith Ligon of Dana-Farber.

The researchers describe Olig2 as a "gateway" gene for the development of brain tumors for several reasons. First, the Olig2 protein is crucial for the development of neural stem cells and their progeny specifically in the central nervous system. Second, the activity of Olig2 is deregulated in brain cancer. And finally, Olig2 activity is required for the formation of some tumors.

When the researchers blocked Olig2 activity in mice that develop brain cancer, 91 percent of the animals did not form tumors. "Our findings identify this core transcriptional regulator as an important candidate for antitumor therapeutics," the researchers conclude.