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What does ‘minimal residual disease’ (MRD) mean for cancer patients?

May 8, 2024
Shimon Slavin

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, a tumor of 1 millimeter in size may consist of approximately 1 million cancer cells. They can divide and spread throughout the body, forming metastases even in distant organs.

For this reason, at Biotherapy International, we do not use the term ‘remission‘ in the context of curing the patient completely. 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’ (also known as molecular residual disease), refers to a small number of tumor cells that remain in the body during or after treatment when the patient is in remission. Initially, the term MRD was used in evaluation for hematologic malignancies, but now it is also applied to other types of cancer.

To determine the stage of minimal residual disease in various types of blood and lymphatic cancer, highly sensitive methods of DNA, RNA, and protein analysis, such as PCR, are typically used. For other types of cancer, so-called solid tumors, the method of liquid biopsy is used to detect remaining cancer cells. This method is an effective way to diagnose minimal residual disease, but it has not yet been widely used in clinical practice.

Why is MRD important for immunotherapy?

In many cases, achieving MRD is the patient’s only chance of complete recovery from cancer. After all, there is a high probability that achieving MRD again in case of recurrence will not be possible, and the patient’s immune system will be too exhausted to fight the malignant tumor. Also, the tumor may change its appearance to evade the patient’s immune system or become resistant to the applied treatment methods.

At Biotherapy International, we strive to achieve the MRD stage in order to apply one of the most promising immunotherapy methods – allogeneic targeted activated killer cancer cells (ATACK method). This method is particularly effective when the number of cancer cells is minimal, and it allows destroying even resistant cancer cells, as well as cancer stem cells from which a tumor can develop again.

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