Conference Vancouver, B.C. June 11, 2001
Speakers
Dr Miller: So the questions we have from a gynaecological standpoint regarding PET scanning are a little bit of uncertainty with regards to the sensitivity and I will say that almost all these questions haven’t been addressed in the other tumour sites earlier this morning.
So we feel in our group that there is a huge potential in gynaecological oncology and that we do need to develop some protocols to validate the technique. Particularly as there is not as much in the literature regarding gynaecological tumours as there is in some of the other sites. And we believe that particularly in evaluating lesions in the pelvis that it may well replace some of the traditional imaging, and we also feel that BCCA would be a great place to test the validity of PET scanning in gynaecological cancer due to well established referral patterns and an excellent registry.
Dr Sutcliffe: Thank you very much Dianne. Perhaps I could just go to our expert panel in two areas:
Dr Coleman: Yes, just to summarise some of the information that we have available. The data on cervical cancer and spread to pelvic lymph node and distal metastases actually is quite strong and may be stronger than some of the other indications that the HCFA will be evaluating in the near future. So I think its utilization in cervical cancer can be justified from the literature that is available to us at this point in time. The uses for the other indications are not as well supported, there is some data on ovarian cancer; there are one or two studies that I am familiar with, a hundred to two hundred patients at the University of Tennessee, Knoxville. Dr Karl Hubner did a very nice study on ovarian cancer. The studies were suggestive that it may be helpful there both for the detection of spread at time of diagnosis but particularly for the detection of the recurrent ovarian cancer the timing of the second look surgery that you were talking about. The problem with ovarian cancer is that it is frequently very small sheets of cells, not in masses, so that makes it very difficult to detect that type of recurrence as compared to nodal recurrence where it is in a mass. You ask about the volume of disease necessary for detection, again it is like the lung cancer or the other malignancies that we talked about, it all depends on the uptake by the tumour and the surrounding tissue uptake to see if you can see it. Generally we are talking about lesions being somewhere between 5mm and 1cm for us to detect accurately but smaller lesions that have more uptake will be detected, larger lesions with less uptake will not be detected.
Dr Sutcliffe: Thank you very much Dr Coleman. Any further comments from the panellists, or the floor, regarding gynaecological cancers?
Dr Wahl: I think the data in ovarian for recurrence versus CT, although the numbers of studies are small, are fairly strong. I think, it is my opinion and there are statistical data in those papers show that for recurrent metastatic ovarian cancer PET is clearly better, I think than CT, even though those numbers are fairly small.
I was interested in imaging ovarian cancer quite a long time ago and at least part of the reason we moved onto lung and breast among other things was that the NIH decided to fund my proposal. I remember my proposal in lung cancer and one in breast and at the time did not agree to fund this ovarian work. It’s sort of hard to know but I think some of the early studies weren’t supported by our government, so you kind of have to do the work that you get supported to do—at least in the environment that I was in which I was located in—but we saw promise to ovarian cancer early on in animal studies; it was one of the first diseases that we looked at in animals and in people and I think there is a lot of potential there.
Certainly 3 or 4 papers recently on cervical cancer; I personally think that it is the method of choice for staging local regional nodes for cervical cancer and I believe anecdotally that there will be a paper coming out shortly showing the prognostic value of PET in cervical cancer which I think is going to be quite useful as well, so I think that is one where it might well be said that these are infrequent, less frequent, diseases and it is hard to have the number of large studies done and if the data are compelling even in smaller studies I think, you are going to delay introduction of a useful technique while you are waiting for large studies in small numbers of patients, and I think that this is one of the concerns overall I have with the disease-based approach to PET.
For patients who have rare tumours their diseases are just going to be infrequent enough that it is going to be hard for PET to get out and have large studies done; so at a point you have to, I think, to make a decision for infrequent tumours that maybe if the early data are suggestive, that the criteria for making the technology available have to be more liberal than in diseases like lung, where you can get you know, thousands of patients, where conditions like ovarian and some of the others are much less common—thyroid is just hard to get the numbers of patients done—just a comment.
Dr Sutcliffe: Argue strongly for this being a site in the provincial context.