Canterbury DHB

Management

Manage indolent systemic mastocytosis (ISM) symptomatically with:

• mast cell blockade and stabilisation, e.g.:
  • sodium cromoglycate
  • H1 blockers
• montelukast
• prevention of osteoporosis e.g.:
  • calcium
  • vitamin D
  • biophosphonates
• H2 blockers for gastric hypersecretion
• adrenaline/EpiPen for systemic anaphylaxis
• glucocorticoids to treat inflammation.

Where possible, avoid triggers for symptoms such as:

• medications (e.g. NSAIDs)
• extreme emotional distress
• exposure to heat and cold
• infection
• anaesthetic
• surgical procedures
• very vigorous exercise

Patients may need prophylactic mast cell stabilisation for even minor procedures, such as bone marrow biopsy. This is best done in an environment where any “crisis” can be safely managed.

In patients who have more advanced, symptomatic disease, treatment options may include:

• imatinib (if no KITC816V mutation)
• cladribine
• interferon
• hydroxyurea

As of July 2018, the most promising agent for patients with advanced SM appears to be midostaurin. This is not currently funded in New Zealand, but may be made available on compassionate supply.

Cytotoxic drugs used for mast cell reduction have included cytarabine and daunorubicin, but are typically only considered for patients with:

• aggressive mastocytosis accompanied by C-findings due to organ infiltration (including cytopenias)
• osteolysis (or osteoporosis) with pathologic fractures
• hepatosplenomegaly with impaired liver function and ascites
• malabsorption

Allogeneic stem cell transplant can be considered as a potentially curative option in appropriate patients with severe disease.

Treatment of SM patients with an associated haematologic neoplasm (SM-AHN) depends upon the specific AHN. The approach is to treat the AHN as if SM were not present, and to treat the mastocytosis as if the AHN were not present, while monitoring patients closely for mast cell activation symptoms during therapy.

For disease-modifying therapies in mastocytosis: current recommendations and emerging new treatment approaches, see Valent P, et al. (2016),² table 4 page 5.

Topic Code: 7928