Conference Vancouver, B.C. June 11, 2001
Speakers
Dr Evans: So in summary Simon here are the indications I think we should be using PET scanning in thoracic malignancy:
Dr Sutcliffe: We are going to enter a discussion session now on these two tumour site presentations lymphoma and esophageal cancer. Ken don’t go away from the microphone or at least stay close to one. The panel session is an open session, an interaction with the audience, our invited faculty and our local faculty and we want to get into a discussion on the indications that have been presented to us.
Maybe we will take esophageal cancer first, Ken you have put forward, you believe that PET should be used at the time of diagnosis of esophageal cancer for those patients who would be appropriate for radical surgery or for a chemotherapy/radiotherapy treatment plan; is that correct?
Dr Wilson: Yes, that is correct. The object obviously is to exclude patients who have distant metastasis from consideration of either treatment and to identify nodal sites perhaps which may be treated either by chemotherapy or by surgery.
Dr Sutcliffe: Perhaps I can pose that to our faculty, would you agree with that recommendation for indications?
Dr Coleman: I certainly agree that that is one indication we have been doing more and more of those at our institution. Another one that I think should be considered is the evaluation of the patient after the completion of the chemotherapy/radiation therapy just to see what their status is at that point and I know at least in some, centres are considering these patients right now for surgery after the adjuvant chemo/radiation therapy. That is something that there is not a lot of data on but something that I know that we are starting to use PET scans for at our institution.
Dr Wilson: As a matter of fact that has been our so-called approved indications for doing PET scanning for esophageal cancer; there being a finite pool of money, we were asked which categories of patients do you think we should focus our attentions on and having undertaken primary chemo- or radiotherapy on these patients—obviously there are two potential radical treatments; we have gone from the non-surgical one first and then the scan is being undertaken to determine disease extent, disease activity and suitability for surgery; I agree entirely that that should be added to the list.
Dr Evans: Esophageal cancer is such a bad disease and we are seeing more of it of course with the increased incidence of adenocarcinoma, and I think that we are going to be seeing it in the younger age group to as related to reflux and what not and from the surgical perspective the surgery of course as major as Dr Wilson mentioned but the surgical results are improving and the mortality rates are getting lower and certainly we do not want to operate on anybody who is incompletely staged or who has metastatic disease and my feeling is that PET scanning should be part of the routine staging work up for esophageal cancer, as well as looking at recurrence after treatment.
Dr Wahl: I would agree I think that data are incredibly strong that it is more accurate than your standard methods for determining whether the disease is localized or disseminated and I think in time we are going to be asking ourselves not the question of whether PET should be done in these patients where I think the answer is yes, but the question of what additional information is provided by CT in these patients and I think that will be remain to be seen but certainly at Hopkins where there is a lot of esophageal cancer seen. We are basically doing PET on everybody prior to the initial decision on treatment to determine whether the disease is localized or disseminated so the data seem very strong—I would agree with you.
Dr Sutcliffe: So you would be saying that at the time of initial assessment for a patient who is technically fit for surgery excluding other co-morbid conditions or general condition if they are eligible and fit for surgery you believe that PET is the standard evaluation?
Dr Evans: Yes I do.
Dr Wahl: So do I.
Dr Shreve: I would have to concur; at Michigan we see the same phenomena, where our surgeons are very interested in finding occult metastasis particularly the retro-peritoneal and the super-ventricular nodes that are not well detected, particularly the super-ventricular nodes on CT and it is becoming routine now to do the PET scan prior to surgery since obviously finding distant metastasis changes the management. Also again we found many times the abnormalities on the CT retrospectively particularly below the diaphragm just isn’t called by our expert CT people.
Dr Baum: I would like to stress a point that to use FDG-PET before radiation therapy, we have done a prospective study of about 60 patients together with our radiation oncologists and looked at the extension of the radiation field before and after PET and in a number of patients which is in the range of 20 to 25% there is much more extended field by the PET determined as compared to the CT alone. So it might be very useful before radiation therapy and also for looking at treatment response.
Dr Sutcliffe: It sounds as if the general philosophy that is coming forward is again in the patient who is fit for operation with esophageal cancer PET would be the single most useful test in terms of evaluation of the disease and that one might argue, CT has relatively little role if you have access to PET in esophageal cancer. I am putting that forward for response or contradiction.
Dr Wilson: I think old habits die hard; it is difficult to believe that CT scanning for esophageal cancer would become extinct anytime soon. Perhaps the surgeons might address that? I am sure there is a comfort level with CT scanning.
Dr Sutcliffe: Just before any colleagues answer, it seems as if we are saying we are looking for evidence-based use of practice. One would argue more strongly that there is less evidence for the use of CT than there is for the use of PET.
Dr Shreve: Yes, I think that may be true, but in the first place that anatomic framework of looking at the body will not disappear quickly and secondly this is something that we will be exploring more completely with the combined scanners—the CT is often helpful in interpreting the PET scan and vice versa. So I’m not sure that we will be seeing the demise of CT for esophageal cancer; more likely the technique we use to do CT in esophageal cancer will change somewhat and will be less aggressive in the use of contrast material with the advent of the combining the CT with PET.
Dr Sutcliffe: Are there any views from the floor? Tom.
Floor: I would just like to know why MRI is not figured in any of these comparisons as a diagnostic tool given its different characteristics—particularly MRI with cadmium and the manipulations that go with it?
Dr Wilson: I don’t know the answer to that question but in all the papers that I reviewed about PET scanning in esophageal cancer the standard, the gold standard, is surgery; the other techniques are CT scan and esophageal ultra sound; MRI was not apparent in any of the studies. I think I listed about 20 of them of PET studies in esophageal cancer.
Dr Coleman: In most of our abdominal imaging colleagues, most of our colleagues who are most familiar with the best way to image these anatomically feel that the new CT technique with enhancement is generally a better study than MRI. There are some circumstances where MRI may be a little better but the literature out there is mainly CT for evaluating most of these malignancies and that is the standard by which we are comparing. If MRI would have been performed in these patients the comparisons would have been between PET with MRI; but for most of these cancers CT contrast enhanced CT is the standard technique for evaluation.
Dr Shreve: You know one of the problems with MRI is the motion in the mediastinum, with cardiac action and respiratory motion. Problems that have not been entirely solved and particularly with a multi-detector CT those motion problems aren’t an issue.
Dr Sutcliffe: Ok I think yes. Ivo?
Floor: The fairly clear statement that if the MRI or the PET scan was positive and showed disease beyond surgical volume, that surgery would not be done but with these recommendations doing PET for all potentially operable patients if disease beyond the primary site was identified that being that radical chemotherapy radical approach would not be taken with respect to the chemo/radiotherapy? Would still be doing that might…
Dr Wilson: The width of the radiotherapy field is in the hands of my colleague Dr Lim, Radiation Oncology and the feasibility of the safety, the feasibility of applying a wider field to cover patient, with a PET scan node positive obviously can only be done on an individual basis.
Dr Wahl: I think it is worth clarifying that PET is remarkably accurate for staging esophageal cancer particularly for distant metastatic disease but it is not perfect and particularly in the study from the University of Pittsburgh there are some instances of false positives in particularly the mediastinum and faint uptake in mediastinum nodes may not represent metastatic esophageal cancer and I think that most reading scans are quite aware of that but if it is say small uptake in the mediastinum node it may well be, at least in my part of the country where I’ve lived in the US there can be patients that have had inflammatory disease that can cause faint uptake. Glucose is measuring glucose metabolism FDG is not necessarily always reflecting cancer so I think that still biopsy proof of metastatic disease if it is an equivocal PET finding not multiple foci for example may still be appropriate but certainly PET would detect and direct you to these areas in some instances it might still be necessary.
Dr Sutcliffe: Yes?
Floor: I am just wondering if PET, I mean if radiotherapy, alters the FDG uptake such that there should be an optimal time frame after radiotherapy to obtain a PET scan?
Dr Wilson: I think that the jury is out on that question? There simply isn’t enough information in the literature about the value of PET scanning post chemo/radiotherapy for example and the optimal time. Locally it has been done when the reaction has settled down usually after the patient has had a CT scan and follow up and an endoscopic examination follow-up with a positive endoscopy obvious a surgical candidate.
Dr Baum: After radiation therapy you have to wait at least four to eight weeks because you have a severe radiation induced mucocytis especially on the esophageal region which can also increase uptake in the upper lymph nodes so it is very useful to wait for a long period after radiation therapy; this is not the case for chemo but for radiation.
Floor: I get the sense that this is not be as accurate for assessing the presence of liver metastasis; is that correct and if so what would be the preferred, should one be using it with CT or ultrasound?
Dr Coleman: Certainly PET is very accurate in detecting liver metastasis, I have not seen a direct comparison of FDG-PET to CT certainly in colorectal cancer you will hear later today, it is more sensitive and specific than CT and in detecting liver metastasis, from my experience I think the same is true for esophageal cancer but I have not seen it broken down but it is going to be very accurate for detecting liver metastasis so I would feel very comfortable with the PET scan.
Dr Sutcliffe: So on esophageal cancer, if I could summarize it would seem that we are saying; in the patient who is fit for surgery it would be recommended that PET be one of the, be part of the initial evaluation of the patient with esophageal cancer to exclude distant metastasis in a patient who is otherwise operable and for a patient who has undergone radical radiation therapy and chemo therapy and whom it is believed that further surgical salvage could be a potential option. Would those two recommendations be consistent with where the US is going?
Dr Coleman: Certainly those are the primary reasons that we are doing PET scanning, both the Blue Cross/Blue Shield Technology Evaluation Centre, and the HCFA now will be paying for PET performed for diagnosis if needed, it generally is not used for the diagnosis but for initial staging and restaging which this would then fit into those categories. So yes.