Why CT scan not pet scan?: Good evening... - The Roy Castle Lu...

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Why CT scan not pet scan?

lucanus15 profile image

Good evening to all. I have a quick question please. As you may know, I finished 4 rounds of Cisplatin Alimta three weeks ago, following on from a lobectomy in March.

Tomorrow I have a CT scan and am wondering why they do that at this stage rather than a pet scan. Can anyone explain please?

Best wishes to all and kind regards xxx

6 Replies

PET scans read the amount of molecular energy being given off and really give no indication of the size of a lesion. A CT gives them details like size and shape.


I would ask your clinical team for the reasoning behind it. I know in my case I have only once had a PET scan on the NHS - which was at my initial diagnosis point. I currently pay to have PET privately every now and then.

When I have discussed it with my oncologist he has said that the CT is sufficient to indicate changes .... and that a PET could always follow if there were concerns raised by the CT. I believe the PET also has the CT imaging down (PET/CT) but think the NHS don’t use it for regular monitoring as it is more expensive scan than the CT and the CT should give them the answers they need for monitoring.

Hope that helps and hope you are doing okay.


I would ask your Consultant. I was diagnosed over 5 years ago and have never had a PET scan. Wishing you all the best xx

PET scans gives pictures showing where there is active cancer in the body.The CT scan is very detailed and gives three dimensional images .You should ask your consultant .It may be that doing a PET scan so soon after your surgery may produce a false positive result as a result of tissue damage/inflammation at the time of the surgery.It can take some time for the inflamed tissues to settle down post operatively

it you have any questions please don't hesitate to contact the nurse led helpline Freephone 0800 358 7200.

Kind regards all the team at the Roy Castle Helpline.

CT is standard for the reasons given - a PET can be really useful for when surgery is required but CT is accepted standard. PET can give a number of false positives/negatives and is not widely available geographically so tends to be 'reserved' for where it has most impact clinically. Do ask your team for any questions you have - it can be too easy to look at online posts here and elsewhere and read about different treatments that others have - it is all decided upon clinically. It's not a case of cost saving and 'cuts' as others often suggest - but in the same way, a child would not be given the same dose of medicine as an adult or a smaller person different doses of radiation than a larger one, the same is more true in lung cancer treatments. So many different aspects are considered before treatments are offered/decisions taken and based on a number of factors of the tumour/cancer itself, other genomic results, any other conditions the patient has, the position/stage/size of the tumour etc etc. There are suggested questions in the booklets online on Roy Castle lung cancer foundation website under 'cancer treatments' - which in themselves are very informative and may reduce the questions you want to ask but have space and suggested questions to ask of your clinical team if they don't. good luck,

Thankyou very much everyone. I understand better now thanks for your explanations. Of course, I would ask my pulmonologist if I felt I could, the same goes for every question I have asked on here. They are not available to answer every question. I'm not sure whether it's the same in the UK but I'm in France and there has been a huge lack of communication with this clinic since the beginning of my diagnosis in January. There is no one to go to, and the same goes for my GP, I need to change as he ignored my cancer for several months and several other things.

For example about two months ago I asked my pulmonologist why it my condition wasn't treated with immunotherapy and he said currently there is no protocol for that. Today at my check up he said we could take out the port as lung cancer will be treated by immunotherapty from now on.

Anyway the scan went well, all is good, check up in six months.

All the best folks xx

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