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Monday, September 19, 2011

Sifting Through the Mammogram Muck

In November of 2009 the United States Preventive Services Task Force (USPSTF) revised its guideline on the use of mammography to screen for breast cancer, recommending against routine screening of women ages 40 to 49, and changing the screening interval for women ages 50 to 74 from annual screening to screening every two years.   This recommendation left doctors and patients alike confused over what to do.  With a backlash of public opinion protesting the new recommendations, organizations such as the American Cancer Society continue to support routine annual screening of women beginning at age forty.

What is a health-conscious woman to do?  Randomized controlled trials (RCTs) have demonstrated reductions in breast cancer mortality in women screened with mammography beginning at 40. Screening is most effective in women ages 50 to 69.  A meta-analysis done in 2009 for the purpose of updating breast cancer screening guidelines found very little benefit to screening women in the youngest age bracket (40-49) with mammography given the lower disease incidence and higher number needed to screen (1904) to prevent one cancer death.
In the United States, the lifetime risk of breast cancer in a woman is approximately 12 percent, or 1 in 8. The risk of a woman developing breast cancer between ages 40 and 49 is 1.45 percent, or 1 in 69, which is why if you are in your forties, you likely know several women who have been diagnosed. The risk between ages 60 and 69 is 3.45%, or 1 in 29. About 5 to 15% of mammograms are abnormal and require further follow up. The sensitivity of mammography for detecting breast cancer is about eighty five percent, with a false negative rate of about fifteen percent. However, because of the low disease prevalence in younger women, the risk of an abnormal mammogram being a true positive is less than ten percent. In fact, for a woman who has annual mammograms each year during her forties, there is an about thirty percent chance of having an abnormal during that decade. Given these statistics and the mixed study results, the USPSTF decided that the potential harm of routine mammography in women ages 40 to 49 outweighed the potential for benefit for most women, with the exception of those at highest risk.

However, recently the outcomes of a very large population based study (the SCRY study) of mammography in women ages 40 to 49 conducted in Sweden were published. In the study, women who had an average of 6 mammograms in 10 years had reduced breast cancer mortality compared with those who were not screened.  The observed “number needed to screen” in order to prevent one breast cancer death was 1252 women. 
What comprises high clinical risk of breast cancer? Family history and prior history of breast biopsy are important.  Increased breast tissue density is also known to confer higher breast cancer risk. Clinical risk calculators may be used to quantify risk. 

What about alternate screening modalities—ultrasound or MRI?  Ultrasound is useful for differentiating a fluid filled cyst from a solid breast mass—however, it has limited utility for distinguishing between benign and malignant solid nodules and also cannot detect in situ breast cancer (DCIS), which typically presents as characteristic breast calcification on mammography.  Breast MRI is a sensitive screening modality and is recommended for women with genetic breast cancer risk—BRCA1 and BRCA2, or with a calculated lifetime breast cancer risk of over 15 to 20%.  Those with prior DCIS, lobular carcinoma in situ, atypical ductal or lobular hyperplasia, or extremely dense breast tissue may also benefit. 
Given the recent recommendations and findings a dogmatic approach to breast cancer screening should no longer be the norm-- the approach should be personalized. Women should be asked about their individual history, clinical risk factors, family history and personal screening preferences during each annual visit.  A clinical breast examination should be performed.  If both history and examination point to low or average risk, I support screening every two years after baseline mammography is performed at age 40.  With additional risk factors, including dense breast tissue, family history, previous biopsy or abnormal clinical exam, I support annual mammography beginning at age 40.  At the other end of the spectrum, at this time I also support continuing to perform screening mammography in healthy and functional women who are over age 75 and whose life expectancy is greater than 10 years. 

Thursday, September 1, 2011

Balancing the risks and benefits of endurance exercise

The health benefits of exercise are well-established.  A recent study published in the Journal of the American College of Cardiology showed that one’s fitness level, as measured a person’s one mile run speed, compared to other cardiovascular risk factors, was the best single predictor of heart attack risk and life span. Studies have shown that regular exercise reduces one’s risk of obesity, diabetes, and hypertension.  Exercise has been shown to benefit mood and alleviate the symptoms of depression.   On a cellular level, telomere length, a marker of mitochondrial health, has been shown to be improved in those who exercise.  Consequently, getting people to exercise more has been adopted as a top strategy of health promotion. 

I am an exercise zealot.  Growing up I swam and dove competitively.  As an 18 year old, fearful of the freshman fifteen, I took on running, and have been hooked ever since.   In my middle age, wanting to cross train more because of increasingly achy joints and muscles, I have ventured into bicycling.  We talk much of the health benefits of these sports, but what of the risks?  While exercise long term may be good, do the risks of injury and accident offset the potential for long term benefit and actually increase health care utilization?  Consider three of the most commonly practiced forms of exercise:  running, swimming and cycling.
As a sport, running carries the risk of overuse syndromes: runner’s knee (patella femoral syndrome), iliotibial band syndrome, plantar fasciitis, stress fractures, piriformis syndrome, and Achilles tendinitis, to name a few. Female runners may suffer from the Female Athlete Triad—amenorrhea, bone loss and disordered eating.   Marathon running is known to be associated with low bone density and may also increase oxidative stress.  Whether or not running is the cause of osteoarthritis of the knee is somewhat controversial.  MRI demonstrates knee abnormalities in marathon runners that are not seen non-runners.  Clearly in those already affected by arthritis or prior injury, running makes the condition worse.  Approximately 1 in 3 runners are injured per year of running.  

On the other hand swimming, as a sport, is relatively safe, unless of course you drown.  It turns out that 36% of swimmers who drown in Georgia are intoxicated while swimming—alcohol and swimming don’t mix. Otherwise, shoulder bursitis and rotator tendinitis are the most common swimming related injuries.

In my view, of the three sports, biking may be most risky. Approximately one in three bikers has an accident per three years of biking.  The annual rate of accident for regular bikers is about one and ten (less than running). However, in comparison with the debilitating overuse injuries of running, biking carries a more profound risk of serious injury and death.  Studies show that the risk of head injury and upper facial fractures may be reduced by 60 to 70% with helmet use.  Legislation requiring bike helmet use has increased compliance with this health-promoting behavior.   There’s also the threat of pudendal nerve injury and for men, erectile dysfunction.  A recent study showed 94% of asymptomatic male, mountain bikers had evidence of scrotal abnormality on ultrasound, presumed the result of chronic repeated microtrauma, compared to 16% of non-bikers who had abnormalities.  Avid bikers will tell you that proper seat ergonomics and padded shorts help reduced these risks of saddle injury.

In a triathalon a couple of years ago I took a hair pin turn too quickly, driving off the road into a grassy embankment.  Fortunately, I sustained only minor abrasions and was able to keep riding.  Others are faced with more serious injury.  Recently, in a tragic accident, a male physician biking across a bridge in Charleston, South Carolina was killed by a passing truck that hit him throwing him off the bridge. Bikes are no match for cars, and it's a drivers world that we live in unfortunately.
I exercise because I like getting outdoors and being active.  It gives me a sense of well-being, improves my mood, makes me more confident about my physique, and seems to keep my weight in check.  I hope it will result in further health benefits down the road.  The positive data seems good, however when prescribing exercise to promote health it’s important to weigh the balance of risk and benefit.   Despite popular notions, the practices of stretching and cross-training have not been convincingly demonstrated to reduce injury. Given the physical diversity of those who exercise and the lack of good data on what helps prevent injury, a common sense approach seems reasonable. Of course, as I write this blog with my calf resting on a bag of ice, talking common sense to an exercise enthusiast can be a challenge.