Minimal Residual Disease in Indolent Lymphomas: A Critical Assessment.

OPINION STATEMENT: Indolent non-Hodgkin lymphomas (iNHL) are a heterogeneous group of pathologies characterized by a prolonged natural history and good response to treatment. They also have a tendency to relapse, in some cases with a worse prognosis. One of the main objectives in the newest clinical trials is to identify patients at high risk of relapse. This cannot be accomplished using only clinical prognostic scores. Detection of minimal residual disease (MRD) is effective in evaluating long-term disease response, with a strong and independent predictive value that was demonstrated in large cohorts of patients. Analysis of MRD allows patient stratification based on the risk for relapse; therefore, different therapeutic programs can be designed based on the response characteristics. This tailored therapy is already happening in current clinical trials. Limits imposed by traditional PCR-based tools are being overcome due to new molecular biology techniques like droplet digital PCR and next generation sequencing. Although these techniques are not yet standardized, they will likely increase the reliability and ensure broad applicability of MRD detection in future years.