Update From the Medical Journals: July 2012
July 31, 2012
By Mary Pickett, M.D.
What's the latest news in the medical journals this month? Find out what your doctor is reading.
Just as daily birth control pills can help prevent pregnancy, daily antiviral medicines can help prevent infection with HIV, according to two new studies. They were published online by the New England Journal of Medicine July 11. (A third study published in the same issue did not find a benefit.) As a result, the U.S. Food and Drug Administration (FDA) approved the drug Truvada four days later. The drug is actually a combination pill containing tenofovir and emtricitabine.
Using Truvada in this way is called "pre-exposure" prevention. It may be useful for people at high risk for getting HIV infection. This includes people who are married to a partner with HIV, or men who have sex with men (HIV is common in this group).
All of the studies took place in Africa and lasted one to two years. The drugs were not a substitute for condoms use of condoms to prevent infection was still encouraged for everyone in the studies. Here's what the studies found:
Not all experts at the FDA agreed about the drug's approval for prevention. People who know they are in a study are more likely to take every dose they're supposed to take. In real life, however, people may not take their pills as regularly. Spotty use of the drug might allow resistant forms of the HIV to develop. The drugs do have side effects, including nausea, kidney and liver irritation and bone thinning.
Doctors are delighted with the way some children with severe egg allergy have responded to a treatment known as oral immunotherapy (oral desensitization). This treatment was successful when tried in children with peanut allergy three years ago. Experts hope that this treatment will prevent dangerous allergic reactions in children who are at risk.
More than 2% of young children have severe egg allergies. They have life-threatening reactions if they eat any egg. Most children outgrow this allergy, but 10% to 20% never do.
Oral immunotherapy works like allergy shots. The idea is to teach the immune system to react to triggers without causing symptoms. But allergy shots are too risky to use for food allergies.
For this study, 55 allergic children were exposed to egg proteins when they swallowed very diluted amounts of egg-white powder on a regular basis. They began by swallowing only trace amounts, and they progressed to a daily dose of about one-third of an egg.
Forty were treated with the powdered egg white; the other 15 were given cornstarch (as a placebo). The amounts were increased every two weeks. The treatment lasted two years. After about a year, half of the children in the treated group were able to eat a small portion of egg in their doctor's office with no reaction. At the end of two years, 75% of the children treated were able to do this with no reaction. None of the kids who got the cornstarch treatment were able to pass the egg challenge. Eleven kids were able to stop the powder treatment and start a diet that included daily eggs. And they stayed healthy. This suggests that the process of oral desensitization may have fairly long-lasting results.
Oral immunotherapy probably works for the same reason that allergy shots do. After months or years of having a small but consistent exposure to your allergen, your body shifts to a different way of reacting to your trigger. You produce IgG antibodies. You also activate cells called suppressor T cells. Your immune system is so busy making these harmless antibodies and cells that it makes very little IgE and histamine in reaction to your allergy trigger.
Scientists caution families of children with a peanut or egg allergy not to try this treatment at home. This process requires great care in giving the appropriate dose of the trigger food.
An expanded study using oral desensitization for peanut allergy is taking place. Doctors are hopeful that within several years, we will know enough about oral desensitization to offer this treatment to far more children with severe food allergies.
In May, the U.S. Preventive Services Task Force (USPSTF) recommended that men without symptoms should not be screened for prostate cancer with the PSA (prostate specific antigen) test. This group pointed to evidence that screening did not help men live longer. But if you have prostate cancer, should you have surgery?
A study released July 19 by the New England Journal of Medicine asked this question. It included 731 men with early-stage prostate cancer. They were randomly assigned to have surgery (removal of the prostate gland) or no treatment. When they started the study, the average age of these men was 67. People in each group lived an average of about 13 years after the study began. There was almost no difference between the two groups in rates of death from prostate cancer or other causes. Some men who had surgery suffered long-term complications.
But there was some evidence of benefit for men with a score of 10 or higher on the prostate-specific antigen (PSA) test. Prostate cancer deaths were 33% lower for men with these higher scores who had surgery rather than no treatment.
What lesson can we take from this study? For men who have low PSA scores and early cancer, surgery may provide peace of mind, but it is not likely to change life expectancy in a meaningful way.
This study was much smaller than planned. It was supposed to recruit 2,000 men. This makes it a weaker study, so we should be cautious how we interpret it. It was hard to enroll men who would leave it up to chance whether they were assigned to treatment or no treatment for their newly diagnosed prostate cancer.
Mary Pickett, M.D. is an Associate professor at Oregon Health & Science University where she is a primary care doctor for adults. She supervises and educates residents in the field of Internal Medicine, for outpatient and hospital care. She is a Lecturer for Harvard Medical School and a Senior Medical Editor for Harvard Health Publications.