Clinical Applications of P.E.T. in Oncology

Speakers

• Dr Helen Anderson, Medical Oncology, Vancouver Cancer Centre
• Dr Simon Sutcliffe: CEO, BC Cancer Agency
• Dr Peter Conti, MD: Associate Professor of Radiology, Clinical Pharmacy and Biomedical Engineering USC
• Dr Paul Shreve, MD: Assistant Professor, Internal Medicine, University of Michigan Medical Centre.
• Dr Richard Wahl, MD: Director of Nuclear Medicine, John Hopkins University
• Dr Richard Baum, PhD: Chairman PET Centre, Zentralklinik, Bad Berka, Germany

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Dr Anderson: (Part of main presentation)

So to summarize Thyroid cancer:

• There is a high level of evidence that PET is useful where post treatment thyroglobulin is elevated and radioiodine scans are negative.
• There is some evidence in the literature that there may be a role for PET as an additional imaging procedure where the radioiodine scan is positive.
• PET may detect fully differentiated clones of cells that are missed by this scan. I would be interested in any of the panel’s comments about whether this is actually being used in their centres. And then the other indications for Thyroid cancer are still under investigation.

So to summarise in Head and Neck cancer:

• There is good evidence for its use in the detection of unknown primary.
• It is useful for the detection of recurrent disease but as we heard before it should not be performed too soon after radiotherapy, as false positives can be a problem with the inflammation associated with radiotherapy.
• Finally, it may be useful in selected patients for staging where it can affect treatment planning and potentially affect outcomes.

Dr Sutcliffe: Thank you very much Helen.

Discussion following:

Dr Sutcliffe: I am going to go onto thyroid cancer: now where I believe there was one strong indication put forward and that was the detection of recurrent disease after definitive therapy on the basis of elevated thyroglobulin in the presence of a negative radio-iodine scan. Correct me if I have said that wrong. That was the one indication that I picked up on. Is there any question as to the appropriateness of that recommendation?

Dr Wahl: The American Thyroid Association has prepared a document, I don’t know if you have seen the draft. I saw the draft recently, which they are sending to HCFA strongly urging their support of PET in the detection of recurrent thyroid cancer. The draft I saw also included the less frequent but equally perhaps more vexing problem of rising calcitonin levels in patients with the history of medullary carcinoma of the thyroid, but this body was strongly in the support of the use of PET in Thyroid cancer.

Dr Conti: Yes, I haven’t published in that area myself. I was very appalled by the fact that HCFA did not approve but specifically called out the lack of support for thyroid cancer. I think that this is a completely underserved population that could specifically benefit from the technology when the alternatives are minimal.

Dr Baum: We are treating about 100 patients a year with thyroid cancer with radioiodine and I must say we have now done routine studies, although in what you mentioned that could be an indication in addition to radioiodine, and I think the most useful indications is in patients with elevated HGG and radioiodine negative whole body scan. But also you see the so-called flip-flop phenomenon of differentiated and undifferentiated lesions in quite a number of patients with follicular cancer and metastases where you detect significantly more disease especially in the bone, which might deserve treatment—also patients with a positive radioiodine scan. So I think the story is not closed. But clearly, the one indication with the radioiodine negative scan is a very good indication.