I’ll be talking about the role of MRD, which is minimal residual disease, in the management of acute lymphoblastic leukaemia of adult patients. I will show how and why this test, MRD, is very important to perform in individual patients to refine the prognostic profile and also to decide about final treatment which normally is standard chemotherapy for the people that we define as MRD negative, I’ll explain it in a minute, and is empowered by allogeneic stem cell transplantations who are defined as MRD positive.
Should MRD overcome baseline factors in risk assessment?
Yes. MRD is minimal residual disease which means it’s the disease itself and it’s measured in patients who achieve a complete remission, so who respond very well to the initial treatment, to initial chemotherapy, and are apparently without any sign of the disease in the blood, in the bone marrow and are clinically free of any symptoms. But we know that some leukemic cells may still harbour in the bone marrow of these complete remission patients and there were highly sophisticated methods developed in the lab for measuring this residual disease. Basically it can be assessed by means of molecular biology or by means of multi-parameter flow cytometry. It allows us to assess whether in a CR, in a complete remission patient, there is still one leukemic cell out of 10,000, of 100,000, normal marrow cells following the first steps of chemotherapy. This is very important prognostic information because patients who still harbour residual disease there is a very high risk of subsequent relapse and we define these patients as high risk patients.
On the contrary, the patients in whom we don’t measure any residual leukaemic cells, we define them as standard risk patients. We are very happy because we know in advance that the relapse risk is much reduced and we can continue, we can carry on, with standard chemotherapy without any intensification and without any transplant procedure. So it’s convenient, it’s more convenient.
Is this different in other patient age groups?
No, it’s not much different. The difference lies in the typology of the patients because the older patients usually express additional risk features with more frequency than children. There are more adverse biological subsets of the disease so we get an inferior MRD negativity rate following the initial chemotherapy. We have worse patients in general so we have inferior results with MRD negativity and we expect higher rates of MRD positivity. It’s a disease more difficult to treat compared to children so this is why it’s worse, including MRD, less positive results.