What does ‘minimal residual disease’ (MRD) mean for cancer patients?
Medically reviewed by Prof. Shimon Slavin, MD. Updated: June 2026
When cancer patients undergo treatment, they eagerly await the results of their tests, hoping to see the word ‘remission’ in the report. If complete remission is mentioned, doctors mean cancer that cannot be detected using modern visual diagnostic methods such as CT scans, MRI, or PET-CT. However, even a very small tumor may contain hundreds of thousands or millions of cancer cells. It is estimated that approximately 1 million cells may be present in just 1 mm³ of tumor tissue. They can divide and spread throughout the body, forming metastases even in distant organs.
For this reason, at Biotherapy International, complete remission is not always considered equivalent to the elimination of all cancer cells. Even in the case of complete remission, there remains a risk of recurrence, as just one cancer cell in the body is enough to give rise to a new tumor.
So what is MRD?
MRD, or “minimal residual disease”, refers to a small number of cancer cells that remain in the body during or after treatment when the patient is in remission. These residual cancer cells may be present in both hematologic malignancies and solid tumors and are often undetectable using conventional imaging methods such as CT, MRI, or PET-CT.
Although the patient may appear disease-free on imaging studies, microscopic numbers of cancer cells can remain in the body and potentially cause recurrence in the future. To detect MRD, highly sensitive molecular diagnostic methods are used. Depending on the type of cancer, these may include DNA, RNA, and protein analysis, liquid biopsy, and other advanced technologies capable of identifying traces of disease that remain invisible on standard CT, MRI, or PET-CT imaging.
Why is MRD important for immunotherapy?
In many cases, reducing the number of remaining cancer cells to the lowest possible level may represent the patient’s best chance of achieving long-term cancer control or complete recovery. If residual cancer cells survive treatment, they may eventually lead to recurrence, metastatic spread, or the development of treatment-resistant disease.
Recurrent tumors are often more difficult to treat than the original disease. Cancer cells that survive initial treatment may develop resistance mechanisms and become less responsive to chemotherapy, targeted therapy, radiation therapy, or immunotherapy. For this reason, reducing tumor burden to the stage of minimal residual disease and subsequently eliminating the remaining cancer cells is considered an important goal of cancer treatment.
Immunotherapy for Minimal Residual Disease
For many patients, the greatest challenge is not shrinking a visible tumor but eliminating the last remaining cancer cells that may survive after surgery, chemotherapy, radiation therapy, targeted therapy, or immunotherapy.
At Biotherapy International, minimal residual disease is considered a potentially important therapeutic window for immunotherapy. When the overall tumor burden is minimal, immunotherapy and cellular therapy may be more effective than in patients with advanced bulky disease.
One of the approaches used in selected patients is the ATACK method (Allogeneic Target Activated Cancer Killer Cells). ATACK was developed by Professor Shimon Slavin as an advanced cellular immunotherapy approach for patients with recurrent cancer, treatment-resistant malignancies, and minimal residual disease. Unlike conventional immunotherapy that relies solely on the patient’s own immune system, ATACK utilizes activated donor-derived immune cells that are specifically directed against cancer cells.
The goal is to help eliminate residual treatment-resistant cancer cells, including cancer stem cells that may survive standard treatment and contribute to future tumor recurrence.
Because the number of remaining cancer cells is significantly lower at the MRD stage, cellular immunotherapy may, in some cases, be more effective at identifying and eliminating residual malignant cells before they can develop into a clinically detectable tumor.
For this reason, patients who have achieved remission and have only minimal residual disease may represent particularly suitable candidates for advanced cellular immunotherapy strategies.
Are You in Remission but Concerned About Residual Cancer Cells?
Many patients are told that no visible tumor can be detected after treatment. However, remission does not always mean that all cancer cells have been eliminated.
Professor Shimon Slavin and the Biotherapy International team evaluate patients with minimal residual disease (MRD), recurrent cancer, and treatment-resistant malignancies to determine whether advanced immunotherapy or cellular therapy may be appropriate.
To learn whether you may be a candidate for ATACK therapy, oncolytic virus therapy, cancer vaccines, or other personalized immunotherapy approaches, submit your medical records for review and schedule a consultation with Professor Shimon Slavin.
