FORTE: Impact of imaging FDG-PET/CT minimal residual disease assessment on multiple myeloma patients
Dr Elena Zamagni - University of Bologna, Bologna, Italy
We presented the results of an imaging sub-study in a prospective study dedicated to newly diagnosed transplant eligible patients with multiple myeloma that we ran in Italy. The name of the trial is the FORTE trial. So within this trial there was an imaging sub-study planned with the aim of confirming the prognostic utility of this imaging technique that would discriminate the prognosis of the patient and also with the aim of using standardised criteria for evaluating the response that we previously proposed to be used in clinical trials and in routine clinical practice.
We were able to prospectively study all the patients at baseline and at the end of induction therapy and prior to maintenance with FDG-PET/CT and to apply to those imaging techniques the Deauville Criteria that we previously demonstrated as useful in this context to apply a certain standardised interpretation for PET/CT in multiple myeloma.
So all the patients were studied in a planned way and they received standardised criteria for definition of positivity and negativity.
We studied 189 patients and what we found was that approximately 70% of them achieved a complete metabolic response as previously defined, that is to say a residual eventual uptake of FDG below the threshold level of the liver. So we used the liver as a cut-off. The achievement of complete metabolic response in these 70% of the patients significantly and favourably influenced both progression free survival and overall survival. So the patients with a complete metabolic response achieved a better outcome.
Also another important result was that the negativity in PET/CT was complementary to the negativity of minimal residual disease as evaluated in the bone marrow by flow cytometry and next generation sequencing. So patients who achieved both negativity in the bone marrow with these techniques and negativity outside the bone marrow by PET/CT experienced the best prognosis in terms of progression free and overall survival when compared to the patients that were either both positive for the different techniques or either positive in the bone marrow or outside the bone marrow. So the achievement of minimal residual disease negativity inside and outside the bone marrow was associated with the better outcomes of the patients.
The importance of this study resides in two aspects. The first one is that we were able to reproduce our previous results, thus applying these standardised criteria for PET interpretation that are based on the Deauville criteria, demonstrated to be reproducible. I think that this is important because it means that everyone, both in routine practice or within clinical trials, can use this definition of complete metabolic response.
The second important point is that PET/CT demonstrated once again to be complementary to bone marrow techniques and thus the evaluation of minimal residual disease, both inside and outside the bone marrow, turns out to be the best way to identify a subgroup of patients with a particularly good prognosis after treatment.