Cancer risk generally low for CT scans

DEAR DR. ROACH >>

I have had two CT scans: one eight years ago of my pelvis and abdomen, and one this year of my brain, neck and chest. I am very worried this will cause me to get cancer. Do I need to be concerned about developing cancer due to these CT scans?

— N.W.

DEAR READER >> Generally, for an individual, the risk of cancer from a CT scan or two is very low.

Whether medical radiation increases the rate of cancer is debated, but most authorities feel that large amounts of radiation, especially when repeated, may increase the risk of developing certain cancers, especially leukemias. Published estimates for the risk of developing cancer from a CT scan range from 0.08% for a single CT scan (at age 45) to 1 in 500 (if done at age 20). Another study estimated a 1.9% increased risk of cancer from 30 years of annual CT scans starting at age 45.

Physicians ordering these CT scans must be aware that there is a cost to ordering them that goes beyond the financial cost.

DEAR DR. ROACH >> Do people develop fewer colds as they age? If so, why? I’m 78 and haven’t had a cold for at least 25 years.

— J.S.B.

DEAR READER >> It is true that older people usually have fewer colds as they age, but that is largely due to being exposed less frequently.

The immune system also is likely to have been exposed to many more viruses as we age, but unfortunately, for some viruses, one can never get high-level immunity to; meanwhile others have so many different strains that it’s likely you will get exposed to one your immune system doesn’t know.