European Breast Cancer Conference, Vienna, March 2012
New technology for identifying and removing micro metastases in breast cancer patients
Professor Michael Douek – Guy’s and St Thomas Hospitals, London, UK
Michael Douek, King’s College London, surgeon with a special interest in sentinel nodes and things in the axilla, tell us all about the session today and your own research.
So a sentinel node biopsy is very much topical subject matter at the moment, following the interest in the Z11 trial data in America and also the data that has come out from Milan that tells us that micro-metastases, perhaps we don’t need to do an axillary node clearance.
You have to stop and define a micro-metastasis now then, don’t you? What does that mean?
A micro-metastasis really is a lesion, a metastatic deposit to a node in the axilla of up to 2mm, in fact just under 2mm in size.
And that’s a micro-metastasis and that does not seem to carry the same adverse prognosis as was thought.
That’s right. The randomised controlled trial presented at San Antonio suggests that there is no difference in survival between an axillary node clearance and not doing one over just under a five year period.
So that puts the extra onus on the pathologist?
That’s right, the extra onus is on the pathologist to distinguish accurately between what is a macro and a micro metastasis.
And that puts an onus on the surgeon to find the sentinel node in the first place, and that’s another area of your special interest.
That’s right. So my special interest is in a new technique for sentinel node biopsy, it’s a hand-held magnetometer called the SentiMag and I use the injection of iron nanoparticles into the breast, a magnetic dye essentially, into the breast, and this then travels to the nodes in the axilla and the hand-held magnetometer allows the surgeon to identify the nodes and remove them.
Let me interrupt you, what’s a magnetometer?
A magnetometer is a hand-held device that creates a small magnetic field within the probe and then there’s a central detector that detects changes in that magnetic field. So when the probe is in proximity to a ferromagnetic source, in the shape of an injection of iron oxide, there are changes that are detected by the probe.
OK, so it will pick up the sentinel node, or more than one?
Yes, the probe will pick up the sentinel node; in a previous study at Guy’s Hospital we’ve been able to show that this does work and the probe has now been CE marked. We’ve had a slight set-back in that the iron oxide we were using was an MRI contrast agent, Endorem, that’s been removed from the market. So Endomagnetics Ltd, the company I’m working with, has developed its own magnetic dye that is the first iron-based magnetic dye that is a CE marked injectable device as opposed to being a drug as such.
So it’s doubly difficult because you’ve got to have a registered injectable and you’ve got to have a device?
So the benefits of this would be, given that the conventional detection methods are getting over 95% of the sentinel nodes, what’s going to be the advantage of using the iron approach?
Yes, the conventional method has a detection rate of in excess of 97%, so the stakes are very high. The main advantages are first of all that it is an entirely novel technique so there will be other applications in breast cancer and in other types of cancers. Secondly, that the technique does not require the use of radiation and some hospitals with no access to nuclear medicine find it quite difficult to perform sentinel node biopsy. So it makes sentinel biopsy potentially more accessible in areas of the world where there is no nuclear medicine access. And of course the other advantage is the fact that the dye itself is black so the node changes colour - when the surgeon identifies it with the probe, the colour change confirms that that is indeed the sentinel node.
And there’s no tattoo?
There is a degree of discolouration, bruising at the site of the injection but in time that fades. But of course those of us who use the combined technique are familiar with the blue staining that we get with blue dye.
And what are the other vehicles around? There has been nanocolloid described at this meeting.
Yes, there’s a technique using nanocolloid which has been described at this meeting, there are various other techniques using indocyanine green fluorescence to identify the sentinel node. The SentiMag multi-centre trial that I have just launched that’s going to be run from Guy’s Hospital and we have six sites. The sub-protocol of the multi-centre trial is to use MRI to localise and characterise sentinel nodes. So this particular technique has the additional advantage that it is combined with a very strong and robust imaging to go along with it, unlike the other techniques that simply facilitate the identification of the node.
Is this a phase II trial at the moment or is it a randomised trial?
It’s a phase II trial that is going to lead on to a randomised trial.
And what will the control arm be?
The control arm will be the combined technique in some centres.
Of? Let’s be clear, what’s that?
So the control arm will be the standard way of identifying the node.
Which is radioisotope alone in some centres now and the use of a combination of radioisotope and blue dye.
Two years’ time you’ll have the results of the phase III trial, Michael?
It’s a surgical trial, we’re going to have the result much before that.
Much quicker than that. Thank you very much indeed, I really appreciate it.