[Richter syndrome successfully treated with ibrutinib monotherapy: two case reports].

The Richter syndrome (RS) is defined as a histologically diagnosed diffuse large B-cell lymphoma (DLBCL) or Hodgkin lymphoma (HL) in patients with chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma. A standard treatment for RS has not yet been established. Most patients with RS are treated with combination chemotherapy regimens used for de novo DLBCL or HL. Recently, the Bruton's tyrosine kinase inhibitor, ibrutinib (IBR), has shown remarkable efficacy in CLL; however, limited evidence exists regarding its single agent efficacy in RS. We encountered two patients with RS in whom CLL transformed to DLBCL, confirmed by G-banding/spectral karyotyping analysis. Both patients achieved durable responses for 12 and 10 months, with IBR alone. Hemorrhagic cystitis due to adenovirus occurred in one patient at an initial dose of 420 mg/day, but a dose reduction to 280 mg/day made long-term continuation of IBR possible. Interestingly, retreatment with IBR alone achieved disease control again for 5.5 and 2 months, after these patients underwent salvage chemotherapies for aggressive relapse.