Treatment of Indolent or Smoldering Systemic Mastocytosis (ISM/SSM) with Low Mast Cell Burden and No C-Findings
This protocol covers patients with indolent systemic mastocytosis (ISM) presenting with 0 or 1 B-findings, or smoldering systemic mastocytosis (SSM) with 2 or more B-findings. Both groups share low mast cell burden and the absence of C-findings and any associated hematologic neoplasm (AHN).
ISM is characterized by low mast cell burden with no evidence of C-findings or an AHN. SSM is defined by the presence of 2 or more B-findings, again without C-findings or an AHN — distinguishing this population from more advanced or aggressive disease subtypes.
Treatment Approach
For symptomatic disease, management focuses on controlling mast cell activation symptoms through anti-mediator drug therapy. The approach involves a combination of agents targeting histamine pathways alongside other pharmacological options. Enrollment in a clinical trial is also a recognised alternative.
Treatment Goals
Response is defined as an adequate improvement in disease-related symptoms and/or measurable improvement of B-findings in ISM or SSM.
References
DOI: 10.6004/jnccn.2018.0088
- ISM is characterized by low mast cell burden, no evidence of C-findings, or an AHN.
- SSM is defined by ≥2 B-findings and no evidence of C-findings or an AHN.
- Histamine receptor type 1 (H1) and histamine receptor type 2 (H2) blockers have been shown to control skin symptoms (eg, pruritus, flushing, urticaria, angioedema dermatographism), gastrointestinal symptoms (eg, diarrhea, abdominal cramping, nausea, vomiting), neurologic (eg, headache, poor concentration and memory, brain fog), cardiovascular (eg, presyncope, syncope, tachycardia), pulmonary (eg, wheezing, throat swelling), and naso-ocular symptoms (nasal stuffiness or pruritus, conjunctival injection).
- Cromolyn sodium is effective for the management of cutaneous, gastrointestinal, and neurologic symptoms.
- Aspirin, corticosteroids, and leukotriene receptor antagonists are useful for the management of symptoms that are refractory to other treatment options.
- Omalizumab, an anti-immunoglobulin E (IgE) monoclonal antibody, can be used for the management of mast cell activation symptoms insufficiently controlled by conventional therapy.
- Standard doses need to be titrated. Higher doses may be necessary for symptoms refractory to standard dose treatment.
- Response assessment should be based on improvement of disease-related symptoms and/or improvement of B-findings in ISM or SSM.