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Does pet scan too soon after radiation cause false positive results?

steinmueller
Posts: 5
Joined: Mar 2010

My husband was recently diagnosed with stage 3A large cell carcinoma. He is in his 4th week of radiation 5 days a week. Next Monday he starts his 2nd chemo round which will end 4/5. We are told that two weeks from his chemo treatment (approximately 4/19) he should have a new pet scan to see how the chemo and rad has worked. If it has responded well they may do surgery to remove the upper left lobe.

My question is I have heard that you should wait 3 months after radiation to do a pet scan and if not you can receive false positive results which if this is true would affect their decision on whether or not surgery was an option. Any one know anything about this?

soccerfreaks's picture
soccerfreaks
Posts: 2800
Joined: Sep 2006

I have not heard this, that one should wait three months after a last radiation treatment before getting one's next PET scan. But there is a lot I have not heard of that is nonetheless the true.

In any case, theoretically the radiation may cause false positives forever, if it leaves scar tissue. It is not alone: scarring from smoking, from old bouts with pneumonia or bronchitis, a current lung infection, all are potential culprits.

This is why your husband's doctors will probably compare this next scan with the previous one I assume he had. They will look for both new growth and the disappearance (hopefully) of some nodules that were there before (now zapped by the combo of rads and chemo -- hopefully).

BUT: bring this concern of yours to the attention of the doctor ordering the scan, first to make sure he/she is aware of the radiation going on (I would hope so, but you never know), and second, to assuage your concerns.

Good luck to hub with his treatment and results!

Take care,

Joe

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