Understanding the Most Common Definition of MRD in Medical Literature

In cancer research, the importance of MRD has been growing, extending its relevance from hematologic malignancies to solid tumors. However, it stands for different definitions according to the specific context: Minimal Residual Disease, Molecular Residual Disease, or Measurable Residual Disease. This variability in terminology reflects the evolving nature of cancer diagnostics and treatment monitoring.

Given the importance of clarity in medical terminology, we conducted a literature review to identify the most commonly used definition of MRD. We employed the search query (“circulating tumor DNA” OR ctDNA) AND MRD AND “[X] residual disease,” with [X] representing one of the three definitions. Out of 250 articles, our analysis revealed that “Minimal Residual Disease” is the term most frequently encountered in the literature (n=185, 74%). This term is primarily used in the context of assessing patient’s outcome, particularly after surgery and/or chemotherapy, in various cancers type, emerging as prognostic factor [1-7]. Conversely, “Molecular Residual Disease” and “Measurable Residual Disease“, less frequently used (n=53, 21% and n=12, 5% respectively), are mentioned accordingly treatment effectiveness [2][8], identifying a specific driver [9], or reporting disease burden [1] and their dynamics [6][11-12]. They also reflect different methodologies and technologies used to detect residual disease, such as next-generation sequencing (NGS) and flow cytometry [3][12-14].  Therefore, both agreement and distinction between these terms have practical implications for patient care, helping in treatment decisions or intensity of surveillance. Similarly, measurable residual disease status serves as a critical endpoint in clinical trials, influencing the development of new therapeutic strategies [3][5][15].

In conclusion, while the term “Minimal Residual Disease” appears to be the most used in the literature, the use of “Molecular Residual Disease” and “Measurable Residual Disease” reflects the diverse and evolving nature of cancer research. As our knowledge of cancer biology expands and diagnostic technologies progress, the terminology for describing residual disease will undoubtedly evolve. Nonetheless, the ultimate goal remains the same: to improve patient outcomes by detecting and treating the smallest traces of disease.