Sudden elevation of plasma D‐dimer levels induced by the combination therapy of dabrafenib and trametinib: Report of two cases

: The combination therapy of dabrafenib and trametinib revolutionized the treatment for BRAF V600-mutated melanoma. Various adverse events have been reported for this treatment, most notably fever. Herein, we report two cases of novel an adverse event, namely sudden and significant elevation of plasma D-dimer level induced by this therapy. In the first case, the remarkable elevation of plasma D-dimer level up to 87.4 mg/dL was noted on day 11, and in the second case, the plasma D-dimer level reached 125.5 mg/dL on day 25. In both cases, D-dimer levels gradually decreased after the cessation of this therapy. Although the exact cause is not clear, we assume two possible hypotheses: the first is that the combination therapy may induce disseminated intravascular coagulation, and the second is that the therapy induced pathological condition of secondary thrombotic microangiopathies. Our cases suggest that this thrombotic adverse event should not be overlooked, and coagulation parameters need to be monitored during the course of this treatment.