Infection protection and breast cancer
Group Health, Fred Hutchinson researchers find antibiotic use may be linked to higher cancer risk
Women with high levels of antibiotic use may have twice the risk of developing breast cancer as those who have not used antibiotics, according to a new study conducted by researchers at Group Health Cooperative, Fred Hutchinson and colleagues at the University of Washington and the National Cancer Institute.
The findings appeared in the Feb. 18 issue of the Journal of the American Medical Association.
Breast-cancer risk doubled among women who had taken antibiotics for more than 500 days or had more than 25 prescriptions over an average of 17 years. But even those who had received between one and 25 antibiotic prescriptions during the same time period had a 50 percent greater breast-cancer risk.
What’s more, the researchers found risk increased regardless of the type of antibiotic.
The findings stem from an analysis of computerized pharmacy records of more than 10,000 members of Group Health Cooperative, a nonprofit health-maintenance organization in Washington state.
The study did not address whether antibiotics cause the increased risk or whether those who need antibiotics have underlying conditions that might cause breast cancer. Such conditions might include a weaker immune system or specific infections. The study also did not examine whether antibiotic use is associated with other types of cancer.
Because the analysis is the first of its kind in the United States, more research is needed before the safety of antibiotic use is questioned.
Dr. John Potter, Fred Hutchinson’s Public Health Sciences Division director and a coauthor of the paper, urged caution regarding the study’s implications and reminded women of the value of breast-cancer screening.
“This is an important finding because the study design is strong,” he said. “But the findings need to be replicated before we go any further. So in relation to a woman’s risk for breast cancer, she should do exactly the sorts of things that she hopefully is already doing — having regular mammograms, remaining physically active and not gaining weight after menopause.”
“Antibiotics have a substantial health-care benefit when they are used prudently to treat bacterial infections, ” said Dr. Christine Velicer, an investigator at Group Health’s Center for Cooperative Studies and lead author of the paper. “If women have concerns about antibiotic use, they should talk with their doctors. But based on this study alone, we would not at this time recommend changes in antibiotic use.”
Velicer also noted that the comparison group — women who never used antibiotics, at least during the study period, which averaged 17 years — could have unusual characteristics that offer some protection against cancer. “Those who have never used antibiotics may represent a unique group that have stronger immune function, for example,” she said.
“Antibiotics are an extremely useful tool for the treatment of infection but should not be misused, such as for treatment of the common cold,” Potter said. “At this stage in the research, these findings are not the basis for personal medical decisions or policy recommendations.
“Right now we want to understand the science behind this finding,” Potter said. “The impact on medical practice should come only after we know that this has been replicated in several more studies.”
Second transplant can help some children with relapsed leukemia
Some children with an aggressive form of leukemia whose cancer returns after a stem-cell transplant can be cured with a second transplant, according to new findings by Fred Hutchinson researchers.
In a study of 25 children with acute myeloid leukemia who relapsed after a first transplant, Dr. Soheil Meshinchi and colleagues found that nearly half of those who underwent a second transplant from a tissue-matched donor were still alive after 10 years.
Not all children who relapse after transplant for AML will survive long enough to undergo a second transplant. But based on their findings, the researchers recommend that those who do and who also meet certain other criteria be considered for the procedure.
“Pediatric AML is a very difficult disease to treat, and patients who relapse after transplant typically have a very poor prognosis,” said Meshinchi, an associate in clinical research in Dr. Jerry Radich’s lab and a pediatric oncologist. “The existing treatments for patients who have relapsed after an initial transplant do very little to improve long-term survival.
“A second transplant would not be suitable for every pediatric AML patient who relapses,” Meshinchi said. “Children who experienced significant toxic side effects from their first transplant would not be good candidates. But for those who have matched donors and other favorable characteristics, a second transplant should be considered.”
Genetic test could predict transplant complication
A simple genetic test could help doctors predict the likelihood that a patient will develop a potentially life-threatening complication after a bone-marrow or stem-cell transplant.
New research conducted by Drs. Ming-Tseh Lin, John Hansen and colleagues reveals that transplant recipients with a common form of an immune-system gene are half as likely as other patients to develop severe graft-vs.-host disease. The complication occurs when transplanted cells mount a destructive immune reaction against a patient’s body.
The findings suggest that including the genetic test in a patient’s standard pre-transplant evaluation could ultimately help doctors determine the optimum timing and course of treatment.
“This clearly supports the hypothesis that genetic variation plays an important role in determining outcome after transplant,” Hansen said.
Agricultural pesticide exposure varies by task
Agricultural workers who thin orchards face a greater likelihood of pesticide exposure than other farm workers, according to a new Fred Hutchinson study.
Researchers found that workers who thinned orchards were more likely to have detectable levels of pesticides in their house and vehicle dust as compared to agricultural workers who did not perform orchard thinning. The study also found children of thinners are more likely to have evidence of pesticide exposure in their urine than do children of non-thinners. These findings support the theory that agricultural workers may track home pesticides on their clothing and shoes.
“Most previous pesticide-exposure research on farm workers has focused on pesticide handlers, such as pesticide mixers, loaders and sprayers, but this study suggests that more research is needed regarding exposure patterns among other types of farm workers as well,” said Dr. Gloria Coronado, lead author of the study. Orchard thinners may be at higher risk for pesticide exposure because thinning usually takes place in the spring, when crops are sprayed to prevent pests.Antiviral drug reduces transmission of herpes
People with genital herpes can significantly reduce their chances of giving the disease to their uninfected partners by taking a single daily dose of an approved antiviral drug, according to a new study led by Fred Hutchinson.
Dr. Larry Corey of the Clinical Research Division and an international team of collaborators conducted a study of nearly 1,500 heterosexual, monogamous couples in which one partner had genital herpes and the other did not. Infected partners who received a standard oral dose each day of valacyclovir were half as likely to transmit herpes simplex type 2 (HSV-2) than infected partners given a placebo.
University of Washington collaborators included Dr. Anna Wald, associate professor of medicine and laboratory medicine, and Dr. R. Ashley Morrow, professor of laboratory medicine.
The strategy could potentially combat the spread of other sexually transmitted diseases caused by viruses, said Corey, head of Fred Hutchinson’s infectious diseases program and UW professor of laboratory medicine.
“This is the first demonstration that an antiviral drug can prevent a viral sexually transmitted disease. It provides the conceptual framework to extend the approach to other viral STDs, such as HIV infection,” he said.
