Effective upfront treatment with low-dose ibrutinib for a patient with B cell prolymphocytic leukemia.

B cell prolymphocytic leukemia (B-PLL) is a rare and aggressive disease that is associated with poor survival. Although initially asymptomatic patients do not require therapy, most patients will progress and inevitably require treatment. More than 50% of patients with B-PLL carry abnormalities in the TP53 tumor suppressor gene and/or complex karyotype and show resistance to conventional chemotherapy. The efficacy of ibrutinib, a B cell receptor inhibitor, for B-PLL with the TP53 abnormality as second-line therapy was recently demonstrated. We herein report that low-dose ibrutinib as upfront therapy induced a complete response in a B-PLL patient with the TP53 abnormality, whose condition has since remained stable with no recurrence for 12 months. Effective treatments for B-PLL are lacking and given its rarity, prospective comparative therapies are not yet available. This case suggests that upfront therapy with ibrutinib improves the outcome of B-PLL.