While some forms of systemic mastocytosis (SM) can be relatively mild, some types can be more aggressive. Treatments also used for cancer are sometimes needed to control the disease. Understanding why means understanding SM’s root cause.
Understanding mast cell growth
In brief, cancer is simply the abnormal, uncontrolled proliferation and growth of cells. This is why cancer sometimes manifests as a tumor, and why they can spread (metastasize) across the body.
A similar mechanism may be observed in SM. In all types SM, a type of immune cells known as mast cells grow and accumulate in various organs in the body. Studies show that many patients with SM have a genetic mutation known as KIT D816V. This genetic mutation causes mast cells to grow uncontrollably and survive against normal mechanisms that should normally block this from occurring.
Because of this abnormal buildup of cells, SM is technically considered a cancer. However, for most patients this label doesn’t mean what we usually think of when we hear the word “cancer”: Patients with milder subtypes of SM have normal life expectancies and do not need aggressive treatments.
In mild cases of SM, the primary symptoms are allergy-like. These can often be dealt with using anti-allergy medications such as antihistaminesAntihistamines Medications that block the effects of histamine, the chemical found in mast cells that is responsible for many of the symptoms of SM, as well as many allergic reactions. and mast cellMast cell A type of white blood cell produced in the bone marrow. They help defend against infections and play a key role in allergic reactions. In SM, mast cells become overactive and build up throughout the body. stabilizers.
But on other cases — and especially in advanced SMAdvanced SM In these subtypes of SM, mast cells begin to damage organs. Advanced SM includes the subtypes aggressive SM, mast cell leukemia and SM with an associated hematological neoplasm. — mast cells proliferate and infiltrate organs in a cancer-like manner. The medications used for less aggressive forms of SM won’t offer sufficient disease control, so cancer therapies are sometimes used, depending on disease progression and severity.
Read more about SM testing and diagnosis
Stronger therapies for stronger results
A class of cancer therapies often used in SM are known as tyrosine kinase inhibitors (TKIs). These work by blocking the mutated KIT protein to inhibit the uncontrolled proliferation of mast cells. Examples include midostaurin, avapritinib and imatinib.
Another type of cancer treatment sometimes used in SM is chemotherapy. The goal of chemotherapy in SM is to reduce the mast cell burden, which means reducing the number of mast cells accumulating in the body. Chemotherapy might be used in some advanced cases of SM if TKIs do not achieve sufficient disease control.
Stem cell transplantation, a treatment used for certain kinds of cancer, is also sometimes used in cases of advanced SM. A stem cell transplant replaces diseased blood cells with healthy ones. This treatment comes with many risks, however, and is usually only used as a last option.
SM is a complex disorder, and doctors take many factors into consideration before deciding on the most appropriate therapy, such as treatment history, family history, treatment response and disease evolution. Each approach is tailored to the individual patient. Cancer therapies are only administered when absolutely necessary as they can cause significant side effects.
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