DEAR DR. ROACH: Radiation can be used to treat cancer, but I’ve heard that radiation from too many CT scans and X-rays can cause cancer. What is the difference? I’m 72 and have had close to 25 CT scans over the years, mostly of my sinuses. Do I have an increased risk of getting cancer? — W.S.
ANSWER: In medicine, all therapies have potential side effects. Some drugs that are designed to stop abnormal heart rhythms paradoxically cause them. Anti-epilepsy medicines increase seizures in some people. That’s why doctors need to individualize therapy based on many factors, some of which initially are unknown.
There is no doubt that radiation therapy is effective for some cancers. Testicular cancer tumors are among the most sensitive to radiation, and early stages of this disease have greater than a 95 percent cure rate when treated with radiation. However, there is a clear increased risk of secondary cancers later on in people treated with radiation. The absolute risk, however, is only a few percent, so perhaps three men of 100 treated with radiation therapy for testicular cancer will develop another cancer.
The net effect of having multiple CT scans is not known with certainty, but most experts do feel that radiation from medical tests imparts a small risk of cancer later on. For this reason, it’s always important for a clinician to think twice before ordering a test with significant radiation exposure (a CT is up to 300 times more radiation than a regular X-ray, and dental X-rays use even smaller amounts. A chest X-ray is roughly the same amount of radiation you’d get in a day from natural sources, such as cosmic rays and radioactive decay in building materials).
In your case, the absolute risk of developing cancer from 25 CT scans is very small. The average person in the U.S. has about a 25 percent chance of death from cancer, but, as a rough guess, someone with as much radiation exposure as you might have a 25.1 percent risk.
DEAR DR. ROACH: I am a 67-year-old woman with a really good doctor who does not do routine urinalysis, but who does regular complete metabolic panels, CBCs, chemistries, etc. I don’t have diabetes or anything wrong with my kidneys. It has been my understanding that my blood test results would reflect any kidney issues. Now my insurance company is pushing for me to have a routine urinalysis. The company will pay me if I have it done! The reason given is that the screen will reflect early kidney disease. Is this really necessary if the abovementioned bloodwork is completed? — M.S.
ANSWER: I am confused by this. “Routine” or screening urinalysis is not recommended except in people with diabetes or known kidney problems. I certainly understand why an insurance company would want you to get a preventive-care service, such as a vaccine; many of these not only keep you healthy but also save the insurance company money by keeping you from getting sick enough to be in the hospital. Giving you some incentive to get recommended preventive services is a great idea, but a urinalysis isn’t a good choice. It is not recommended to obtain one in healthy women, and isn’t a good choice for detecting chronic kidney disease. A blood test would be appropriate for people at higher risk, such as those with high blood pressure or diabetes.
Insurance companies are not known for giving money away for no reason, so maybe yours knows something about you (or thinks it does) from your previous medical records that makes a urinalysis a good idea.
Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or request an order form of available health newsletters at 628 Virginia Dr., Orlando, FL 32803. Health newsletters may be ordered from www.rbmamall.com.

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