Question about PET scan

[jw2000]

My cousin was diagnosed with breast cancer. She had the surgery and it was OK. But they found another tumor in the lymph at where her neck meets her chest. She did a PET scan and it showed that the tumor was not active. But before the PET scan she had gone through the 1st session of her chemotherapy(The CAF proccedure). The PET was done 25 days after the chemo. We have 2 question about the PET result,
1. Does the chemotherapy affect the PET result? Do the checmicals suppress the glucose activities so that the PET won't be able to catch it? If so how long after can PET be performed again?
2. She had a very small dosage of injection before the PET scan. But some patients that did the same PET scan said the dosages they had  are a lot more than that. Can you tell me about how much of the liquid is suposed to be injected for a regular PET scan?
Thanks

[CCF-RN,MSN-rf]

Dear jw2000:  First off, the PET scan is not a perfect test.  The fact that it did not indicate activity in this tumor does not mean it is benign.  Likewise, it does not indicate that it is malignant.  The role of PET scans in many illnesses is controversial.  If this tumor is still there, a biopsy would be more conclusive.  Theoretically, a PET can be done at any time.  Theoretically, if a tumor is metabolically active, it will show up at any time.  But the PET is not perfect.  The dosages given prior to pet scan are specific to the scan and the patient I would avoid comparing perceived dosages with other patients the amount of liquid may not be an indicator of dose.

[surgeon]

the usefulness of PET scans, and at what time to do them, is still not entirely clear for all situations. I think the best thing is for her to ask her doctors specifically what they had in mind in ordering the test, what info they wanted to gain, and how they are interpreting it and why. Ask specific questions like that, and I'd bet you'd find out what you want to know.

[jw2000]

Thanks for the quick response. But her doctor is a pain to ask questions to. That's why I'm posting this message to see if we can find the answers ourselves.
John

[surgeon]

I'd add that I'd assume the PET was done to look for tumors in places that are not known; in other words, less to evaluate the known tumor, than to see if there are others. If the situation you describe means they found a lump but haven't tested it other than the PET scan, as has been said the only way really to know about it is to sample or remove it. If there's a lump there, the PET doesn't really tell anything about it that isn't already known; namely, that it's there. The scan isn't so reliable as to be able to say with certainty that the lump is or is not malignant; unless the strong impression of the doctors is that it's not a malignant lump, and they had a reason for doing the scan rather than biopsy.

[jw2000]

Thanks again to all for your help. She also did ultra sound and consulted a few doctors on that. Some doctor said it was benign and some said it was malignant. But from what we were told the PET is more reliable than ultra sound images, isn't it? Since she is in the mid of the chemotherapy (she has had 2 sessions as we speak), is it a good idea to have the tumor removed now, or should we wait till the therapy finishes?
John

[jessica803]

I don't mean to sound stupid or dumb. But what is a PET Scan?  I have CT and Bone Scans are they like them? I have a question what kinds of pain management is there for my type of cancer? I currently take MS Contin twice a day and take Perocet every six hours for pain.  But they dont seem to be helping me any, and was wondering what other types of treatment was available for me.  Thanks Jessica803