Large‐cell transformation of chronic lymphocytic leukemia and follicular lymphoma during or soon after treatment with fludarabine–rituximab‐containing regimens: natural history‐ or therapy‐related complication?

Novel therapeutic regimens containing purine analogs and monoclonal antibodies have led to significant improvement in the course of indolent lymphoproliferative diseases (LPD). Complete clinical and even molecular remissions have been achieved in an increasing proportion of patients. In parallel to their tumor cytotoxic effect, these agents are inevitably associated with prolonged immunosuppression inherent to their mechanism of antilymphocytic activity. Until now, attention has been paid mainly to opportunistic infection occuring as a result of the above drug‐induced immunosuppression and less to other possible complications, such as malignancy or tumor progression in the immunocompromised host. Here we briefly report nine patients with previously treated indolent LPD in whom the onset of large‐cell transformation occured during or shortly after the initiation of regimens containing these agents before transformation occured. One patient had received rituximab alone, three fludarabine‐containing regimens and five received sequential regimens containing both agents. This ‘switch’ in the histopathology could merely reflect the natural course of progressive lymphoma and be unrelated to the therapy given. The onset of this complication during, or so soon after, administration of these regimens seems to us more than just a chance relationship in these cases; however, we have no conclusive evidence to prove this hypothesis definitively. We draw attention to this phenomenon.