Minimal residual disease

Minimal residual disease (MRD), also known as molecular residual disease, is the medical condition in which small number of cancer cells persist in a patient either during or after treatment when the patient is in remission and that cannot be detected with current medical imaging or routine screening options (occult stage of cancer progression).

MRD detection is strongly associated with cancer recurrence, often with a lead time of months relative to other forms of clinical evidence. The presence and quantity of MRD are significant because these residual cells can potentially multiply and cause the cancer to relapse, and therefore detecting MRD has significant clinical and diagnostic potential.

Sensitive molecular tests, often minimal invasive and done through a liquid biopsy, are either in development or available to test for MRD. These can measure minute levels of cancer cells in tissue samples, sometimes as low as one cancer cell in a million normal cells, either using DNA, RNA or proteins. Monitoring is performed every three to six months. MRD assessment is increasingly used, particularly in hematological malignancies like leukemia and multiple myeloma, as a powerful prognostic marker and to help guide treatment decisions. MRD monitoring may also be performed as part of research or clinical trials.