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Harvard Commentaries
Harvard Commentaries
Reviewed by the Faculty of Harvard Medical School

What Your Doctor Is Reading What Your Doctor Is Reading

Update From the Medical Journals: August 2013

August 30, 2013

By Mary Pickett M.D.

Harvard Medical School

What's the latest news in the medical journals this month? Find out what your doctor is reading.

Expert Group Recommends Yearly CT Scan For Heavy Smokers

Yearly computed tomography (CT) scans can reduce your chance of dying from lung cancer by a small amount, if you are a heavy smoker. Beginning last year, the American Cancer Society (ACS) recommended that heavy smokers consider screening with a yearly CT scan to find early lung cancers. Now, another expert group, the U. S. Preventive Services Task Force (USPSTF), is also making this recommendation.

While preliminary, it is likely to become final within the next several months. This group's recommendation is important, because Medicare covers services that the USPSTF recommends.

The recommendation was published July 29 in the Annals of Internal Medicine. According to the USPSTF, the CT scans should be limited to people who are at highest risk for lung cancer, and who are most likely to tolerate surgery and gain years of life if cancer is found. Screening could be beneficial if all of these are true:

  • You are between 55 and 79 years old
  • You are in good enough health that you could safely have surgery
  • You have smoked the equivalent of a pack per day for 30 years (2 packs per day for 15 years would qualify
  • You are either a current smokers or a recent quitter (within the last 15 years)
  • You can have the screening tests done in a medical center where there are experienced radiologists and cancer specialists

Our best data on how well CT works for smokers come from the National Lung Screening Trial. This study, published in 2010, monitored smokers who had a spiral computed tomography (CT) scan once a year. The spiral CT shows the lungs in detail, so it can find small cancers. People who got the CT scans were 20% less likely to die of lung cancer in the 5 years after beginning screening, compared with smokers who got X-rays.

A 20% difference sounds like a lot. However, it's important to consider how many people need to be tested to potentially save 1 life. According to the same 5-year study, in order to save 1 smoker or former smoker from dying of lung cancer, 303 people needed to get a yearly CT scan.

The scans were not a perfect test. One out of 4 people had a false-positive test. That is, the scans showed possible lung cancer, but additional testing showed there was no cancer after all. A false-positive test can lead to unnecessary surgery. Another problem with the tests is that it involves repeated exposure to radiation. From the available evidence, the USPSTF has estimated that the benefits outweigh the risks.

The best way to prevent lung cancer is to stop smoking. If you have been a heavy smoker, you can consider having a yearly CT scan to look for lung cancer. This test may find a lung cancer while it is small and most easily treated.

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New Screening Approach May Detect Ovarian Cancer Early

Ovarian cancer is one of the most challenging cancers to treat. It can occur at a young age, compared with other cancers. Only 25% of all ovarian cancers are found early enough to be treated and cured. Doctors have hoped for a screening test that would help identify ovarian cancer much earlier than we can now. If so, maybe more women could survive this cancer.

Two existing screening tests are ultrasound and the CA-125 blood test. (High levels of the CA-125 protein can sometimes be a sign of cancer, including ovarian cancer. But the test is not very specific.) Overall, having these screening tests every year would only reduce deaths from ovarian cancer by about 11%. This is too small a number to make the cost of testing worthwhile for women at average risk.

But a new screening strategy has shown promise, according to a study published August 26 by the journal Cancer. The study included 4,051 women who volunteered to participate. Each woman got the CA-125 blood test at the start of the study. Based on her age and her CA-125 result, each woman was categorized as being low, intermediate or high risk for ovarian cancer. The low-risk women were asked to wait a year before repeating the CA-125 test. The intermediate-risk women were asked to have a re-check in 3 months. The high-risk women were given ultrasound tests and referred to a cancer specialist. Every time a woman in the study had a CA-125 test, her risk category was re-calculated. Researchers were looking for small increases in blood test results. Roughly 93% of women were categorized as low risk each year, so not very many women needed the extra testing.

After following this screening plan for 11 years, the researchers  found 4 women with ovarian cancer. All of them had early-stage cancer that could be cured by surgery. Although this is a small number of lives saved, it could be an economical way to screen for this cancer.

So far there are no screening guidelines for ovarian cancer. Women who have a family history of ovarian cancer or who carry a BRCA gene are at high risk. The most effective way to protect yourself against ovarian cancer, in this situation, is to have the ovaries surgically removed. The long-term use of birth control pills can cut the risk for this cancer in half. Having a tubal ligation (having your "tubes tied") also seems to lower the risk for ovarian cancer.

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More News In Brief

    • Probiotics Fail to Prevent Diarrhea in Elderly. Diarrhea is a common problem after antibiotic use. Probiotics contain "friendly" organisms that are normally found in the digestive tract. Many people eat yogurt or take other forms of probiotics to prevent antibiotic-associated diarrhea. But a new study released online by The Lancet August 8 had some disappointing news. About 3,000 hospitalized patients, all over age 65, received antibiotics for a variety of reasons. The researchers hoped to show that you could prevent antibiotic-associated diarrhea by giving "friendly bacteria" during and after use of antibiotics.

      For three weeks, half of the patients took a probiotic pill that had the kinds of bacteria that are usually found in a healthy gut. The other patients took a placebo pill. There was no difference between the groups in the number of people who developed diarrhea. It was about 10% in both groups. A specific cause of diarrhea associated with antibiotics, known as Clostridium difficile or "C. diff" infection, was also equally common in both groups.

      The best way we have to prevent antibiotic-associated diarrhea is to avoid antibiotics when you do not need them.

    • Higher Blood Sugar Increases the Risk of Dementia. Even without diabetes, people with mildly elevated blood sugar have an increased risk for high blood pressure, cholesterol problems, obesity and heart disease. Now, high blood sugar is being linked to dementia, according to a study in the New England Journal of Medicine on August 8. The study included 2,067 people ages 65 and older. Only 232 of the participants had diabetes at the start of the study. All of the participants had a series of blood sugar tests. Most had at least five tests in the first few years of the study.

      Researchers averaged the blood sugar numbers for each patient to cancel out variations due to what participants ate or when they ate. Each participant also took tests measuring their mental skills. The study tracked patients for almost 7 years to see what happened as they aged. By the end of the study, 524 of the people had developed dementia (mostly Alzheimer's). What was remarkable was that people who had higher glucose (sugar) levels had an 18% risk of developing dementia compared with people whose glucose was consistently low. This was true even without diabetes.

      It is not clear whether the high blood sugar levels contributed directly to dementia. And this study can't say whether treatment of blood sugar might affect risk. Still, it is prudent to eat healthy foods and exercise regularly, to avoid the changes in metabolism that can lead to higher blood sugar levels.

    • Calcium Channel Blockers May Raise Risk for Cancer. A study of Seattle-area women has raised concern that long-term use of calcium channel blockers (a common group of blood pressure medicines) may increase the risk for cancer. Examples of drugs in this class are amlodipine (Norvasc), felodipine (Plendil), nifedipine (Adalat) and diltiazem (Cardizem). The study was published online August 5 by JAMA Internal Medicine.

      Women in the study were ages 55 to 74 years. Most of them were included because they had a recent diagnosis of cancer -- 880 had invasive ductal breast cancer and 1,027 had invasive lobular breast cancer. 856 women who had no cancer were also invited into the study for comparison. Researchers looked at the women's history of medication use. Women with either of these types of breast cancer were more likely than average to have taken a calcium-channel blocker for 10 years or longer. Using special calculations, the researchers figured out that taking one of these drugs for 10 years more than doubled the risk of cancer. Breast cancer was the only cancer that was studied in this group's research, and the study did not look at cancers in men.

      This study did not find any link between other types of blood pressure medicines and cancer. These included diuretics, beta blockers and angiotensin receptor blockers ("ARB" medicines).

      Calcium channel blockers are usually reserved for people with difficult-to-control blood pressure. Uncontrolled high blood pressure is a serious life threat, so these drugs have an important medical purpose. This study only observed patterns, so it can't prove that the drugs played a role in causing cancer. But while this cancer connection is being explored more thoroughly, it seems reasonable to choose other blood pressure medicines first.

    • Ultrasound Treatment Can Speed Healing of Leg Ulcers. On August 1, a news release from the National Institutes of Health described a simple new treatment that may be able to help leg ulcers heal. It is a battery-powered ultrasound patch that is worn on the skin like a bandage. The patch was most effective when used for 15 minutes at a time, 4 times a day, according to a small study. Leg ulcers are usually the result of poor circulation in veins. Edema (fluid) accumulates in the legs, leading to breakdown of the skin. It can be hard for open skin (an ulcer) to heal. Researchers think the ultrasound treatments might recruit cells called macrophages to the wound, where they can help it to heal. The full report of this small study will be published in the Journal of the Acoustical Society of America. A larger study needs to confirm results before the device can be made available for use.

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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.

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