Can monitoring minimal residual disease levels in CLL predict outcomes?

This study assessed if monitoring the minimal residual disease (MRD) levels in chronic lymphocytic leukemia (CLL) can help guide future treatment strategies. 

This study concluded MRD monitoring can be used to predict outcomes and may help guide future treatment choices.

Chronic lymphocytic leukemia is a cancer of the bone marrow. It is often associated with older patients and abnormal genes. It can lead to abnormal cells of the immune system. FCR chemoimmunotherapy is used to treat CLL. This includes a combination of fludarabine, cyclophosphamide, and rituximab.

MRD is the name given to small numbers of leukemia cells that remain in a patient during or after treatment. It is the major cause of relapse in leukemia. Undetectable MRD (U-MRD) is when the number of cells is so low they cannot be detected. It is unknown if MRD monitoring can be used to predict treatment outcomes in CLL, or if it can help guide future treatment strategies.
 

285 patients were included in this study. They were treated with up to 6 courses of FCR. These patients were followed up for an average of 57 months. MRD levels were tested after 3 courses of FCR, and at the end of treatment. 

Overall, 96% of patients had a response to treatment. 64% of patients went into complete remission. 18% of patients had U-MRD after 3 cycles of FCR. At the end of treatment, 48% of patients had U-MRD. 

After 3 cycles of FCR patients with levels of MRD ≤1% lived for a longer length of time without cancer progression compared to those with MRD >1% (73 months vs. 41 months). After the third cycle of FCR, patients with an MRD level of ≤1% were more likely to have U-MRD at the end of the trial, compared to those who had higher MRD levels (64% vs 9%). 

85 patients with U-MRD at the end of the trial were followed up with yearly blood tests. MRD returned in 38 patients. On average, this occurred 48 months after the end of the trial. 

This study concluded that MRD monitoring may be useful in predicting treatment outcomes in CLL, and guiding future treatment strategies.
 

This study did not evaluate how changing treatment strategies after achieving U-MRD can affect survival. Further studies are needed.