Minimal residual disease status after inotuzumab ozogamicin in patients with relapsed/refractory acute lymphoblastic leukemia

This study aimed to investigate if minimal residual disease negativity is useful as a prognostic factor after inotuzumab ozogamicin treatment in patients with relapsed/refractory acute lymphoblastic leukemia.  

This study concluded minimal residual negativity with complete remission is associated with a better survival in these patients.  

Inotuzumab ozogamicin (Besponsa; InO) is a monoclonal antibody used to treat relapsed/refractory acute lymphoblastic leukemia (r/r ALL). Minimal residual disease (MRD) is the name given to a small number of cancer cells that remain after treatment when the patient is in remission. It is the main cause of relapse in cancer. Negative MRD is a key prognostic factor of outcome in ALL. 

It was not known if MRD negativity is useful as a prognostic factor for survival at the end of InO treatment.  

This study involved 164 patients with r/r ALL who received InO treatment. Of these patients, 121 (74%) had a complete response (CR) or a CR with an incomplete hematologic response (CRi; when the blood cells are not within normal ranges yet). 

MRD negativity was maintained in 76 (63%) patients at the end of treatment. Patients who were MRD-negative with CR/CRi had a significantly improved overall survival (OS; by 48.8%) and progression-free survival (PFS; by 57.7%) when compared to MRD-positive patients.  

The average overall survival was 14.1 months for the MRD-negative group compared to 7.2 months in the MRD-positive group. The average PFS was 8.6 months in the MRD-negative group compared to 5.4 months in the MRD-positive group. 

Of the 121 patients receiving InO treatment who achieved CR/CRi, 65 (54%) had a stem cell transplant (SCT). Patients who had an SCT and had MRD-negative status had an improved OS compared tho those with MRD-positive status. 

This study concluded that among patients with r/r ALL who received inotuzumab ozogamicin, those with MRD-negative CR/CRi had the best survival outcomes, particularly if they had an SCT afterward. 

This study was funded by Pfizer, the manufacturer of inotuzumab ozogamicin. This study included a small number of patients. Also, patients selected for SCT were younger and healthier than those who did not have an SCT. This might limit the conclusions that can be drawn from this analysis.