Midostaurin in Advanced Systemic Mastocytosis

To the Editor: Advanced systemic mastocytosis 1 carries a poor prognosis. 2 Midostaurin, an inhibitor of tyrosine kinases, targets KIT mutants associated with mastocytosis. 3 The French National Reference Center for Mastocytosis (CEREMAST) conducted a prospective survey of patients with mastocytosis who were treated with midostaurin under a transitory-use authorization program. All the patients provided written informed consent. From August 2012 through April 2015, a total of 28 patients with mastocytosis (including 4 with aggressive disease, 18 with associated hematologic non–mast-cell disease, 3 with mast-cell leukemia, 1 with mast-cell sarcoma, and 2 with progressive smoldering disease) received midostaurin at a dose of 100 . . .