So here we are again. We’re still in Nice for the fourth International Workshop on Acute Leukemia. Now we had another discussion a bit earlier, which was indeed on novel treatment strategies in ALL. Now here we are going a bit more specifically. Although we already mentioned alluded to MRD, defined MRD as minimal or measurable residual disease. So this early afternoon, we had a session dedicated to that in fact, the title was new frontiers in MRD for ALL clinical practice. Now one of speakers was virtually is not here with us today, Sabina Chiaretti is here. And, let’s try and go over this because this has become very clearly during the whole session, the whole meeting, I would say from earlier this morning it’s very clear that in ALL, MRD should be a primary endpoint of treatment. If we want to cure patients, we have to obtain a status of MRD negativity.

I wish to add to this that in ALL what we aim or we should aim to is molecular negativity, less flow. I’m saying this because you’ll probably hear about AML and in AML I think it’s a bit less defined because largely by flow, which may be a bit more unpredictable. In ALL, this is a natural must. So I think we should discuss now I mean, theoretically can do MRD by flow, by quantitative PCR. And these are the two main technologies. And by PCR, it means either by immunoglobulin or T-cell receptor gene arrangements or, if you have a gene mutation, a gene fusion by monitoring the infusion.

But that may not be the whole story, because I don’t know if we said it here but this morning. But let’s say it here. Even by molecular, there’s some cases that can be difficult to define because there’s a signal that is, what can I say, minimal signal, and it’s not easy to define. So, one of the issues here, new frontiers in MRD, can we refine, Can we improve further on MRD monitoring? So, Sabina, maybe you should comment a bit on this, but this was your topic, and Nicola, which also was in a session, also discussed this. So let’s try to wrap up a bit what came out from the..

I think you made the two points that were very correct. First of all, that as far as possible in acute lymphoblastic leukemia, which is the first disease in which minimal residual disease really was shown to have an important prognostic rule. So whenever possible, we should not use a flow cytometry but molecular targets. And we have two techniques either fusion genes, which are applicable in for in about 40% of patients where they indeed have fusion gene at diagnosis and the second technique is immunoglobulin T-cell receptor genes. This is somehow the gold standard in which we are starting at now. In general, the cutoff for defining patients either MRD positive or MRD negative, is now 10 to the minus 4..

In ALL.. I’m saying this to bounce in because in AML they were discussing earlier 10 minus three. So in ALL we consider 10 to the minus four. Historically, up to 10 years ago. Also in ALL it was 10 to the minus 3, and then it became 10 to the minus 4.

Right now, the results are improved a lot in terms of, outcome of patients, and therefore we want to see them improve even more, and we are trying to identify better and better certified the patients that become MRD the negative. But then, at certain point, they relapse, and we are lucky enough to have new techniques. And among the new techniques, we have at least two approaches, one is digital droplet PCR, and the other one is next generation sequencing, which means that we are able to design… for which we can identify several, Ig and T-cell receptor markers. So we are at the beginning of the stories, but there’s already quite some data that shows that through digital droplet PCR, which somehow it’s more applicable and also by next generation sequencing, we better can refine minimal residual disease and therefore probably certify better patients and also make more biologically driven therapeutic strategies.

And later we will see what happens. Because indeed, one point that is, that was made today, and we always have to keep in mind. How far must we go to define the patients who are MRD positive or negative? Also, to avoid over-treating the patients when it’s not necessary.

I think it’s important to stress that these technologies are potential refinement. But the gold standard is quantitative PCR. And then I say that in the guidelines, that is what is considered. The new technologies might take over, but today, quantitative PCR, in fact, in studies, for instance, our GIMEMA studies, we add these technologies to standard molecular quantity monitoring… we add that to see if that can further refine which is a very important point, because this is so far translational. So in the trials, then we will show if there is an advantage or not.

Again, important that data should come from trials and should be standardized. That that’s one of the key points again. I mean, we made this point. At least I made it frequently that I mean, if you’re using a laboratory test to modify treatment or to guide treatment, this has to be done in a certified, should be done in a certified laboratory with standardized technologies because, I always bring the example that, blinatumomab has been approved for MRD monitoring. So in ALL, that’s what we’re talking about now. I mean, if you decide if you take a clinical decision that could even be transplant out of a protocol, decide to transplant or not based on MRD, and thus you give or you don’t give, for instance.. in transplant, that MRD test must be done according to the rules. If it’s an in house,

technique carried out and you take a very important decision and the patient might not go well and something goes wrong and the test was not done correctly, this could open some very serious ethical and legal issues. So one has to be very careful. I think this is a very important to underline this, because one thing is research. One thing is applying a lab test to clinical decision. And then talking about an acute leukemia, this could be, it could be transplant or non-transplant, which is obviously a very important decision. So these are very important points. The other point I mentioned in a different setting in another recording we did is again, since MRD is becoming so important, how widely is it doable? I mean, that is the point, I mean, in clinical studies, which we always say that clinical studies should always be done. We would like in an ideal world 100% of patients enter the clinical protocol because clinical protocol is the best way of treating patients.

And clinical protocol, in most countries in Europe, we run these protocols and then some other countries too. But in the minority of the world, if you have a study, then you have a central processing of the lab. So you have the diagnostic work up, the monitoring all done in given laboratories. This should be done. And this is one of the major issues. So a patient that is not in a clinical trial is, unfortunately I would say, less thoroughly managed and processed in a laboratory. And this is one of the key points. And since we’re talking about MRD, and the session exactly, new frontiers, this means that MRD is key in a matter of ALL.

So I mean, this means that the fork between the lucky countries and the less lucky is becoming bigger and bigger. I mean… We even heard this morning that in a very sort of advanced country, like in the US the difficulty of doing MRD in the clinical practice outside the clinical study. This is the US It’s not talking about the middle of nowhere, but these are the realities in the management of a disease like ALL, whhich changed dramatically over the years, where you can cure many patients, and let’s make it very clear. But you have to do all the tests in the best possible way, including MRD.

Another point that came up. But I think it wasn’t this session, but we’ve discussed many times, what happens if a patient becomes sustained MRD negative? Let’s take the example of Philadelphia because the Philadelphia uses a tyrosine kinase inhibitor. I mean, can we consider stopping treatment? Is this fiction?

Not, In my opinion, this is not fiction. It’s something that should be really our next frontier in ALL. Because there are some patients, and we have quite a big experience on them in which, in fact, we have sustained molecular responses for five years, So maybe those patients likewise CML, which is somehow the step nephew. We could stop therapy. Obviously, this is at least in my opinion, as a clinician, it’s something that has to be thought very seriously. So the molecular response must be sustained probably at least for five years. And this decision must be taken also with the patient because indeed, we’re not speaking about minimal residual disease molecular laboratories. But after that, there is a patient, and such a kind of delicate decision must be taken with them as well. There is a single published experience from the MD Anderson, in which they reported on nine patients who did suspend treatment, and for the majority of them, the response is continuous and they continue to have a molecular response. In a single case, there was a molecular relapse and apparently restarting treatment led again to a molecular response, thus suggesting that it’s something that at certain point more and more must be in the back of our mind. That must be the next goal.

Yeah, I think we have to be very cautious. I wouldn’t like… people may decide to stop. CML is a chronic disease. You stop treatment in molecular responses after a long period, but if they relapse, they can easily be retreated with the TKI and the response. So it’s not a big issue. You don’t have an acute leukemia, so it obviously, I think we have to keep that in mind for the future. We’re not there yet, but the fact that we’ve been talking about it means that we’re getting further, so it could happen in the future. I don’t know. So far, I think it’s a bit premature. But if we continue these good figures and after many years having shown and maybe with the new technology we discussed here, if you can show also by digital drop and NGS that it’s completely negative and has been for years and years, maybe maybe one day we might even consider stopping it.

Okay, Was there a point we brought up? Probably not. There’s anything else now, so I don’t think so. And that’s obviously not only for the Philadelphia positive, but also Philadelphia negative, even T-ALL. I mean, let’s say just to finish that virtually all ALL patients can be monitored for MRD. This is very important because this obviously is an added value of ALL.

Okay. So I hope we convinced you, first of all the importance of MRD, the role it plays in the correct management of ALL of all ages. But again, another point. It’s not only for the younger patients. we’re treating now elderly patients in the Philadelphia positive with no age limit, but even in the Philadelphia negative is going to improve with these new antibodies. So I’m sure that this is going to extend to all ages and MRD must be applied at all ages.