DEAR DR. DONOHUE: I am due to have a mammogram in July, but around the same time I am supposed to have a chest CT as a follow-up to my chondrosarcoma cancer. I have a CT every other year, and an X-ray on the opposite years of both my affected arm and my lungs. Does a chest CT have the potential of showing a similar finding as a mammogram? I would just as soon not have to expose myself to so much radiation all in one month. I'm 66. There is a history of postmenopausal breast cancer in my family, in my mother's mother. -- T.M.H.
ANSWER: A mammogram is an X-ray that is designed specifically to look for abnormalities in breast tissue. Mammograms have been extensively studied and proven to reduce mortality in women between the ages of 50-74 (outside these ages, there remains extreme controversy).
CT scans are X-rays taken from many angles and then reconstructed in a computer to provide a look at many slices of the part of the body being looked at. A CT scanner can be set to emphasize bones or soft tissue, and work is ongoing now with CT scans designed specifically for breast abnormalities. The CT scan you get as follow-up to your chondrosarcoma (a rare cancer of cartilage) is designed to look in lung tissue for abnormalities, and has not been evaluated as a means of screening for breast cancer, although I do know that some may be found anecdotally.
The CT scans you get as a part of your cancer follow-up are not an adequate substitute for ongoing mammography, which is particularly important in your case due to a family history. I do understand the concern about radiation, but a mammogram has very little radiation -- approximately the same you would get from naturally occurring radiation sources in seven weeks of walking around.
DEAR DR. ROACH: I read a news report that vasectomy increases risk of prostate cancer. Should men avoid this procedure due to concern for prostate cancer? -- T.S.V.
ANSWER: Several studies have looked at this possibility, and the results are conflicting. A 2014 study of about 50,000 U.S. men showed an increase of about 15% in the risk of fatal prostate cancer, but a 2016 study of 360,000 U.S. men showed no increase in risk. In June 2019, a study of over 2 million Danish men showed a 15% increase in overall prostate cancer risk. To put the risk in perspective, about 500 men would need to have a vasectomy for one additional man to get prostate cancer, in the Danish study. It is not clear that the vasectomy caused the prostate cancer.
It is possible that there is something about men who choose vasectomy that puts them at higher risk to begin with; however, the authors were unable to find a known risk factor to support that possibility.
Even if vasectomy does lead to an increased risk of prostate cancer, it still has similar or lower overall risk than other forms of birth control, and is a good choice for a man who is absolutely sure he does not want to father any more children, as a vasectomy should be considered permanent. Attempting reversal is possible, but there is no guarantee of success.