I have noticed over the last few months that just about every one on these boards talks about PET scans.Robin has never had one ,and there has been no mention of him having one since his treatment finished .Is this another UK/USA anomaly?

Liz in the UK

Liz - I'm glad you asked that. . . Altho' my son had a PET/CT scan before his surgery, there has not been any mention of a PET scan since he completed Rad treatment on 12/19/06. All he had was a chest X-ray on 4/23/07. I don't think it is a UK/USA thing but I've been wondering the same thing. I notice that Robin's stage was T1 and my son's stage is II. Could that be it? All the doctors he's seen since the end of Tx tell him everything is fine.

Wow what a quick reply. Rob had an upper body CT scan but he didnt have anything injected into him,He just lay down on the bed and was passed through the machine .one thing i found very disturbing was when we were told there was no test post radiotherapy to see if the cancer was all gone.

Liz in the UK

My understanding of the PET/CT combination (usually performed at the same time) is that the PET shows abnormal soft tissue growth with astonishing detail, but it does not show the bony structures well, so location is not always as precisely indicated as is desirable. The CT is very precise about location, but it doesn't show the detail of the soft tissue as well as the PET, so often they are paired to show the growth AND the location in detail.

One reason not to do a PET too soon after treatment is that the PET shows increased metabolic activity within tissues. After treatment, there is usually too much inflammation in the tissues to get a true reading.

Does this jibe with the information that you more knowledgeable people have? What is the follow-up most usually given after treatment?

I was told I would get a CT scan a few months after treatments end. The rest of the follow-up care involves only visual inspections. It wasn't very reassuring and I'm assuming it was because I was Stage I.

All,

There are no set protocols for follow-up care and depending on the surgeon, oncolgist, hospital, etc. there are many different approaches taken.

I, for one, have never had a PET/CT scan or any scans, but do get an annual chest x-ray. That is all that my surgeon prescribed as a follow-up. Perhaps this is because I was staged as a T1NOM0.

Someday there may be standard protocols available, but as of now, I'm not aware of any.

Jerry

I had both a PET and CT as part of initial testing prior to Dx but only CT scans post TX so far. I haven't asked why no PET nor have I been told along the way.

Bill D.

Mmm varied responses to my question make me think it is down to oncologists preference.I wonder why?

Here is my understanding, from a layman's perspective.

CT Scan (particularly with contrast) is great for showing structures -- i.e. bony or soft tissue growths -- tumors, lymph nodes, etc. However, by itself, it cannot definitively determine whether a growth is cancerous -- there are certain characteristics that can provide a clue on CT, but nothing diagnostic.

MRI is basically the same in terms of function, though through a different mechanism. Some doctors prefer MRI for clarity in soft tissues, but CT with contrast is close. Again, however, there is nothing definitive in terms of cancer diagnosis.

PET (Positron Emission Tomography) actually visualizes cell activity. You are injected with a radioactive isotope that binds to glucose, which cells use for food. Since cancer cells are "hyperactive", they consume glucose at a much higher rate. This shows up as a "hot spot" on the PET scan. Unfortunately, many types of inflammatory processes also show as areas of increased activity on PET scans, as the immune system cells also consume glucose at a higher rate when battling infection or inflammation.

Thus, most CCCs in the U.S. use a combination of the CT and the PET. If an area of increased uptake coincides with a mass seen on CT, it is highly likely to be malignant. PET is fairly sensitive as well, catching very small cancers.

In terms of the difference between U.K. and U.S., I can only hazard a guess, based upon my travels in the U.K. and Canada. Scanning technology, as a rule, is less prevalent under the nationalized health model than it is here. Friends from Canada routinely come here to Ohio or to Michigan to receive MRI, CT and PET scans, due to the difficulty getting scans in Canada. I have heard the same thing from friends in England.

PET is a newer technology than CT, and even here, the number of machines is much smaller than CT or MRI. It is likely the supply of PET scanners - and the ability to rely on the CT scan + biopsy to achieve the same result.

This is my take on it.
As already indicated the PET scan looks for metabolic anomalies while the CT scan looks at the morphology (structure). The PET scan also may indicate spread more clearly. Both of these are used for planning IMRT treatments and are performed together (generally ?). You need to know which areas to zap and which to protect, for this a 3D representation is needed which shows where the cancer is or is suspected to be after surgery for instance.


Markus

Colleen,
you have it backwards. The PET/CT is very accurate because it is a PET combined with a CT scan and shows very clear anatomical reference points and bone structures. The PET by itself is less accurate. Many times PET scans are given only once in the diagnostic work up as a triage technique to determine if the cancer has spread. Although a few here have regular PET scans, many do not. It is not part of the NCCN Oncology Practice guidelines for regular followup so I suspect that many insurance companies won't pay for them. In early post Tx they are also prone to false positives because of the glucous uptake of the scar tissue. It is also the most expensive scan, the radioisotope, injected by IV, has to be manufactured on a cyclotron and delivered within hours of use by courier. It is also a very long scan taking about an hour to complete.