Update From the Medical Journals: January 2011
January 31, 2011
By Mary Pickett, M.D.
What's the latest news in the medical journals this month? Find out what your doctor is reading.
We don't have good treatments for lung cancer. The only exception is surgery for lung cancer that is caught early. But a new study suggests that a breast cancer drug may give us an invaluable new way to fight lung cancer. This study was released online by Cancer on January 24.
According to the Geneva Cancer Registry, breast cancer affected 6,655 women in Switzerland during a 23-year period covered by the registry. Forty of these women also developed lung cancer.
Researchers looked at the medical histories of these women. They wanted to see if lung cancer survival was affected by breast cancer treatment. What they found was very exciting.
About half of the women who had both cancers had been treated with the drug tamoxifen. (Tamoxifen blocks the effects of the hormone estrogen.) These women were 87% less likely to die from lung cancer than women who didn't get tamoxifen for their breast cancer.
We know from previous research that there are estrogen and progesterone receptors on the surface of lung cancer cells in a fairly large number of lung cancer patients. Tamoxifen is an anti-estrogen drug. It's common for women being treated for breast cancer to take this drug for five years. The strong association between tamoxifen and lung cancer survival suggests that estrogen may stimulate some lung cancers to grow. This would explain why tamoxifen use was linked with better survival.
More studies are needed to confirm this benefit. But it's likely that lung cancer patients and their doctors will begin using this treatment without waiting for more studies. The risks from tamoxifen treatment are fairly small, and the drug may be life-saving.
On January 6 the New England Journal of Medicine published two studies that appeared to promote antibiotics to treat irritable bowel syndrome (IBS). The studies, however, were disappointing.
The researchers credited the antibiotic treatment with improving symptoms for about 1 out of 10 people with IBS who had previously had frequent diarrhea. It was not clear from this study whether the benefit would last longer than a few months. The study did not look at people who had IBS with constipation but no diarrhea. They are not expected to benefit from antibiotics.
The studies included 1,260 patients. Half of the people received rifaximin (Xifaxan), an antibiotic that is used to treat travelers diarrhea and bacterial overgrowth in the intestine. The other half received placebo pills. The treatment lasted two weeks.
Forty-one percent of people who took the antibiotic had "adequate" clearing of symptoms. This number is not much higher than what the placebo group experienced: 32% reported complete or "adequate" relief of pain, bloating and diarrhea symptoms for at least 2 out of the first 4 weeks in the study.
Bloating symptoms improved in 30% of placebo patients and 40% of patients in the rifaximin group. In general, improvement could only be attributed to the drug in 9% to 10% of patients due to the high rate of improvement in the placebo group.
A subset of patients with IBS may have symptoms related to overgrowth of bacteria, or in some way may be sensitive to bacteria in the gut. But it's not clear that antibiotic treatment provides enough of a benefit to be worth the risks.
Based on this study, we don't know how long the benefits from rifaximin will last. Experts are already worried that this study could lead to the widespread use of the antibiotic, perhaps even repeated courses of treatment in the same individuals. Overuse of antibiotics leads to the development of multi-drug resistant bacteria, which is a dangerous problem.
A new way of scanning the brain may allow us to more accurately diagnose Alzheimer's disease, according to a study published January 19 in the Journal of the American Medical Association (JAMA).
We know from autopsy studies that brain deposits of a protein known as beta-amyloid are a hallmark of Alzheimer's disease. But they can't usually be seen on a brain scan. This study looked at an experimental imaging chemical, florbetapir, that binds to beta-amyloid deposits. Florbetapir is mildly radioactive so it can be seen on a positron emission tomography (PET) scan. A PET scan combines several imaging techniques computed tomography (CT) scan, nuclear (radioactivity) detection tests and three-dimensional model construction by a computer. PET scans are also one of our most expensive medical tests.
In the study, 29 elderly people (some with and some without Alzheimer's) and 74 younger adults got a PET scan. Researchers had to wait until all of the elderly people had died and had autopsies to analyze the results. The elderly people's scans matched reasonably well with the autopsy results 15 out of the 29 elderly people had Alzheimer's disease that was confirmed by autopsy, and the test and autopsy results agreed for 28 out of 29 people. None of the 74 healthy young people had positive scans.
The U.S. Food and Drug Administration (FDA) has not yet approved florbetapir for use outside of research studies. It is considering safety data and considering the usefulness of the test. The FDA is concerned about false positive and false negative readings. That's because the people reading the scans sometimes had different opinions about what they saw before a scan was considered positive or negative for Alzheimer's disease.
It's likely that there will be more variation (and more wrong diagnoses) if florbetapir is approved for use by doctors. With such a small study, we are not able to say whether there are conditions other than Alzheimer's disease that might give a positive result (potentially, giving a false positive diagnosis for Alzheimer's).
Even if the test is accurate, doctors are unsure if the cost can be justified. Currently, a PET scan usually costs several thousand dollars. We don't yet have very effective ways of treating Alzheimer's disease, so early diagnosis might not substantially improve care.
However, this new scan may make research easier. If Alzheimer's can be accurately diagnosed in early stages, and the progress of the disease can be monitored by a scan, it will be easier to study new drugs that might treat the disease.