Cancer risk in CT?

[Ho0v-man]

Had an attending comment today about how we’re going to cause cancer in a patient because she’s had 30 CT and/pelv scans over the past few years for abdominal pain. Well I agree that it’s excessive to say the least, the patient is 63 years old.

Trying to find data on this in an older population. I keep finding stuff showing relationships to CT scanning and eventual development of malignancy in peds, but essentially nothing after age 45. Most stuff seems pretty vague too. But maybe my search just hasn’t been very good.

This wasn’t a radiology attending as I’m still in my prelim year. But still curious how much I should care about this starting in a few months. Thanks.

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[bobjonesbob]

Had an attending comment today about how we’re going to cause cancer in a patient because she’s had 30 CT and/pelv scans over the past few years for abdominal pain. Well I agree that it’s excessive to say the least, the patient is 63 years old.

Trying to find data on this in an older population. I keep finding stuff showing relationships to CT scanning and eventual development of malignancy in peds, but essentially nothing after age 45. Most stuff seems pretty vague too. But maybe my search just hasn’t been very good.

This wasn’t a radiology attending as I’m still in my prelim year. But still curious how much I should care about this starting in a few months. Thanks.

The only real data is extrapolated from nuclear accident and atomic bomb survivors so who knows. The risk is likely real but quite small.

 

[Clean7795]

We don't really understand radiation biology well enough to say how high the risk are. Basically radiation after a certain point will definitely overwhelm the body's DNA repair/antioxidant mechanisms and cancer risk increases, and we know that in pediatrics that this occurs even in diagnostic level doses of radiation from CT. The relative risk increases seem quite high based on the pediatric data, though the absolute risk remains low.

It sounds a bit ridiculous but we don't even know if the risk of cancer from multiple diagnostic CTs is worse than from a treatment from radonc, since the energies they use are very different and have strong cytotoxic effects. All we really know is that 30 CTs is presumably a lot worse than 1 CT.

 

[2brads]

I don't have literature, but in fellowship we were told that it causes sarcomas on the order of decades (like 20-30 years post exposure). Usually XRT or VERY heavy diagnostic CT/fluoro exposure. I would be not very concerned for a 63 yo.

 

[Clean7795]

I don't have literature, but in fellowship we were told that it causes sarcomas on the order of decades (like 20-30 years post exposure). Usually XRT or VERY heavy diagnostic CT/fluoro exposure. I would be not very concerned for a 63 yo.

Soft tissue is less radiosensitive than the abdomen. It doesn't make sense to me that sarcoma would be main concern unless we're talking about the fluoro operator getting their hand in the beam.

 

[2brads]

I think sarcoma was mentioned because it is sometimes attributable to prior radiation exposure. The odds of getting such a rare cancer in a part of the body known to have been exposed to radiation are too great to be explained by chance alone. Therefore, I think our attendings were warning us that because of the known link, if a sarcoma were to occur in the future it could potentially be a malpractice issue (particularly with pediatric patients). Whereas, I’m sure other cancers are also caused by radiation, but it is much harder to causally link them with prior radiation. E.g. if a woman gets breast cancer and had a prior chest ct, who’s to say what role the radiation had on an otherwise common malignancy?