explaining radiation risk (CT, etc)

[witzelsucht]

what are your go-to lines to explain relative risk of CT radiation? i've heard people say "equal to about one year background radiation" to get someone to agree, and "1-2% of all cancers are caused by CT"

do you have separate stump speeches for pro-scan and against-scan?

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[DeadCactus]

I usually don't bother with absolute figures. I tell them the risk of [bad diagnosis] and radiation induced cancer from one study are both low but that I think [blank] is more likely.

 

[dotcb]

"The risk of causing cancer from radiation is real, but it is very low risk - much lower than 1%"

https://www.aliem.com/2011/paucis-verbis-lifetime-attributable-risk-of-cancer-from-ct/

 

[gutonc]

"The risk of causing cancer from radiation is real, but it is very low risk - much lower than 1%"

https://www.aliem.com/2011/paucis-verbis-lifetime-attributable-risk-of-cancer-from-ct/

Thanks for this. This is a conversation I have pretty much every day.

Usually with people that already have cancer who are freaked out about the risk.

 

[evilbooyaa]

Thanks for this. This is a conversation I have pretty much every day.

Usually with people that already have cancer who are freaked out about the risk.

Same here. People asking about dose of radiation from CT scans or PET scans for surveillance, when I'm discussing how I'm gonna blast them with way higher doses (albeit focally) for treatment. Patients don't want population studies, they want THEIR risk.

 

[DocEspana]

If its a woman under 40 and I need to give contrast *and* image between the sternum and the vagina I generally give them a speech. If its not all four of those things I generally save the speech for people who look anxious. The society for radiation techs made a nice website that conglomerates all the data we have on lifetime cancer risk from radiation. I generally gloss over the fact that all of our data is based on nuclear bomb and nuclear generator meltdown victims and extrapolating and thats really a terribly way to measure controlled medical radiation.

But yeah, if youre not irradiating breasts or ovaries and youre not young the risk really falls off pretty quickly. But get all of those things together and you get some funny high numbers.

You have a 1 in 500 chance of *inducing* an eventually fatal cancer with a CT PE study on a young female. 1 in 580ish with CT abd/pelv with contrast. But head or extremities? its microscopic cancer risks. And men can basically add 50-100 to all of the cancer risk numbers because of less cancer-prone fatty tissues and a slightly lower lifespan meaning less total cancer.

Most people seem pretty calm when you either tell them that you think the risk of what may kill them is much higher than the risk of cancer (your truth milage may vary) and are *really* content when you tell them their lifetime cancer risk is only raising by 0.1% or 0.2% (even though those are pretty terrifying numbers in reality)

 

[gutonc]

Same here. People asking about dose of radiation from CT scans or PET scans for surveillance, when I'm discussing how I'm gonna blast them with way higher doses (albeit focally) for treatment. Patients don't want population studies, they want THEIR risk.

Just yesterday I got "hey, Dr. RadOnc told me that the radiation I got for rectal cancer would increase my risk of prostate and bladder cancer, how high is that risk?".

Me: "Go ask Dr. RadOnc...and show up for your surveillance CT in 6 months.

 

[evilbooyaa]

Just yesterday I got "hey, Dr. RadOnc told me that the radiation I got for rectal cancer would increase my risk of prostate and bladder cancer, how high is that risk?".

Me: "Go ask Dr. RadOnc...and show up for your surveillance CT in 6 months.

Seen a couple of cases the other way around - h/o prostate radiation, presents with anal cancer. N = 2 so far.

You have a 1 in 500 chance of *inducing* an eventually fatal cancer with a CT PE study on a young female. 1 in 580ish with CT abd/pelv with contrast. But head or extremities? its microscopic cancer risks. And men can basically add 50-100 to all of the cancer risk numbers because of less cancer-prone fatty tissues and a slightly lower lifespan meaning less total cancer.

Those numbers seem high, especially for only one CT. Link to your source would be appreciated.

Saw a thread in related that seemed relevant and had some cool stuff in it:
http://forums.studentdoctor.net/threads/psa-radiation-risk.1130893/

 

[DocEspana]

Seen a couple of cases the other way around - h/o prostate radiation, presents with anal cancer. N = 2 so far.



Those numbers seem high, especially for only one CT. Link to your source would be appreciated.

Saw a thread in related that seemed relevant and had some cool stuff in it:
http://forums.studentdoctor.net/threads/psa-radiation-risk.1130893/

http://www.xrayrisk.com/calculator/calculator.php
Like i said before... the only raw data we base our radiation cancer risk data on is hiroshima, nagasaki, chernobyl and a handful of other reactor leak/exposure situations. The data from these sites is *quite good* but its also from a very specific sort of radiation with a ver specific innoculation. We then worked backwards (and forwards and sidways) to build risk stratifications based on other research but always referring back to these initial studies to figure out the milliseverts required for this and that. There is a widespread belief that the data from these events isn't directly applicable to medical radiology, but given we literally base *all* of our science off of it at a foundational level, we sort of have to use these numbers that no one really believes fully. Had a very long discussion with a few radiologists about this and apparently radiologists basically all understand the conundrum but have no solution for how to make high quality research actual radiation in humans and its lifetime cancer impact.

I feel my sexual assailant hero (David Newman) discussed this conundrum at length on one of his smartEM podcasts and how the numbers we cite probably grossly inflate the cancer risk, but that sort of error is baked into all of our understanding of what is dangerous vs safe in radiation if the nuclear bomb data isnt applicable to the GE Scan-o-tron exposures.

 

[canigetawhatwhat]

If they need it: let's get a CT scan
If its suspect: we can order a CT scan today however I wouldn't be surprised if it is negative. The risk of CT scan is radiation, contrast, increased bill. I am more than happy to order the scan however I think going home and seeing what happens with follow up with your PCP is reasonable as well

Some type of speech like that

 

[BAM!]

Has there been any research aside from nuclear disasters which demonstrate increases in cancer related to medical imaging? I seem to remember something about docs who do a lot of fluoro getting brain cancers.

 

[gman33]

I tell them we have no good information on the risks of radiation. There is probably some increased risk of developing a cancer; but there are no great studies to give us an exact number.

Then I explain why I think they should or should not get a ct.

I can't wait until the day that we learn us and MRI both increase ca risk for reasons not even on the radar of current science.

 

[DrDrummer]

Has there been any research aside from nuclear disasters which demonstrate increases in cancer related to medical imaging? I seem to remember something about docs who do a lot of fluoro getting brain cancers.

I think that had to do with laterality of brain tumors in interventional cardiologists -- there's a left-sided predominance, which may suggest (I don't think there's enough data to make strong claims) that it's related to on-the-job irradiation.

https://www.ncbi.nlm.nih.gov/pubmed/23419190

 

[DeadCactus]

Not a great study, but we do have some evidence beyond nuclear catastrophes.

http://www.bmj.com/content/346/bmj.f2360

 

[ProfMD]

There is also this one in children:
http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(12)60815-0/abstract

Worth noting that head CTs have substantial radiation to brain and bone marrow, increasing risk of brain tumors and leukemia.

Also, different tissues have different susceptibilities to radiation, head and neck being higher than chest and abdomen.

This is a big pet peeve of mine since I see patients all the time who have had unnecessary CT imaging studies. The best thing to do is only order scans when they are needed. The next best thing to do is work with your radiology group to optimize imaging protocols. There are numerous ways that they can tweak the scanning protocols to minimize radiation while maintained diagnostic quality.