I just completed 8 weeks of chemo and 37 days of radiation; my oncologyst now wants me to take a cat scan in 4 wks and a pet scan in 6 wks.

Why does he need both scans? Is this necessary?

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The CT scan is an intensive look at your lungs and any other organs being scanned for the smallest visible "nodule" which may be the sign of a developing tumor. If you had a CT before treatment, the CT scan after allows your Oncologist to precisely see how the treatment has affected your tumors. They can measure shrinkage down to sub millimeter level. A PET scan is a crude way to take a scan of your whole body to see if (hopefully not) your tumor has gone to other parts of your body like bone, brain, etc. It is a much cruder way to detect tumor and certainly does not offer precise measurements anywhere close to the millimeter range.

So CT will show how well you are doing with your treatment and PET is just to assure you that the cancer has not spread elsewhere. Both are pretty easy to take and no pain or discomfort involved.

Lots of Peace of Mind to be gained.


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Thanks for that explanation,TK-my husband just had both,I was not sure why,although i figured since he can't have more Chemo(Cis/etop almost did him in after second week,)they wanted to see what his status is-helps to see it explained that way.
I'm not so sure about the peace of mind part yet :(
Best to you,

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Thanks for the explanation.


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Hopefully your husband has found peace of mind. It is very difficult swimming in these waters but your lifeguard helped me better understand.


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I disagree with TK. My understanding is this:

A PET/CT done together shows where cancer is in your body. The first 3 minutes is the CT scan and the remaining time is the PET.

The only test my Onc orders ate PET/CTs.

This is the best test for cancer mets etc.

My 2 cents.


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The PET scan will also light up any area that may be malignant. There can be false positives, such as scar tissue, as we all know. However, cancer will show up on a PET scan before it can be detected on a CT scan.

Good luck and God Bless.

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Kat is correct. A PET/CT is the most accurate, however insurance companies are denying them.
But I would still ask...

They may be planning to do a CT and then a PET/CT. That's what they did for my husband after treatment. They will refer to it as a PET....but if you check the very well may say PET/CT.

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PET/CT is done Kitkat said. It's not like two apptmts. or even two machines. Make sure that Dr. puts "Re-staging Lung Cancer" on the order---that usually ensures that insurance will cover it.

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Hello, am new tto this site and would like to share my experience on this topic.

I was diagnosed with non-small cell lung cancer, stage 3b, last January 2010. I had a ctscan guided fine needle biopsy which confirmed the type of cancer and did a full body ctscan after for the staging.

I started treatment end of January with chemo concurrent with 33 days of radiation. Finished treatment end of March because I had to stop treatment in between because of the side effects of both radiation and chemo. At one point towards the end of my treatment, I was hospitalized due the bad side effect of the radiation and also had blood and platelet transfusion which delayed further my treatment.

After 6-8 weeks post radiation, we took it upon ourselves to have a PET/CT scan done, although my Oncologist said that a CT scan would do. From the beginning, we were wondering why a PET/CT was not requested.

To make the long story short, I had the PET/CT scan and brain MRI done as suggested by a Singaporean Oncologist who happened to be visiting in our country and I was fortunate to see him for a second opinion since I was supposed to start on a maintenance chemo. He was adamant that I should have a PET/CT and brain MRI done (which he said should have been the protocol for proper staging) to make sure that the cancer has not spread, which the CT scan won't tell you. By the way, I had a CTscan done prior the PET/CT and showed that my tumor has shrunk remarkably, the reason why I have to start on maintenance chemo.

True enough, the PET/CT showed that I have metastases in my bones and brain, and the brain MRI showed the same results. Now, whether these where already existing prior my first treatment, no one can say because these were never shown in the original full body ctscan I had and was not also seen in the post chemo and radiation ctscan I had.

Questions start to pop out, was I properly staged? Was I given the right first line treatment? Did the chemo work (cisplatin/etoposide) or just the radiation? If I didn't have the PET/CT scan and brain MRI done, how will the brain mets be treated since I have no sysmptoms at all. Brain mets are best treated with radiation, I was told.

I went back to my Oncologist and brought him the results of the PET/CT and brain MRI. Immediately, I underwent 10 days of bone and brain radiation, which I just finished 2 weeks ago and I started on Tarceva yesterday.

After 6 weeks, I will have another PET/CT scan done to evaluate and see condition of the mets seen prior radiation.

I hope this help show the value of a PET/CT scan.

Thank you.

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Thanks for the procedures you went through. They are very confusing to the the laymen but you were lucky enough to be guided by a knowledgable doctor.

Good luck to you and we hope for the very best.


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