Radiolabeled MoAb Allows Higher RT Doses

LOS ANGELES--Use of a radiolabeled monoclonal antibody in patientswith relapsed B-cell lymphoma may allow higher doses of radiationto the tumor and less toxicity to normal organs, Oliver W. Press,MD, PhD, of the University of Washington Medical Center, Seattle,said in his ASCO presentation.

In this NCI-funded phase II trial, the CD20 antibody, known asB1 (supplied by Coulter Corporation, Miami), was conjugated tohigh doses of iodine 131 (345 to 787 millicuries). After a therapeuticdose given by injection, patients received either peripheral bloodstem cell or bone marrow support.

Of 25 patients enrolled in the study, all with B-cell lymphomaexpressing CD20 that had relapsed after at least one round ofconventional chemotherapy, 22 exhibited favorable localizationof the radiation to tumor sites after a test dose, and 21 receiveda therapeutic dose.

Seventeen patients had a complete response, and 16 have remainedprogression free for up to 3 years. At a median follow-up of 1year, overall survival is 93% and progression-free survival is62%.

All patients had severe neutropenia and thrombopenia; there wasone fatal infection and one serious case of cardiopulmonary toxicity."Nevertheless, short-term toxicity was less than we haveexperienced in Seattle with our conventional transplant regimens,"he said.

Dr. Press concluded that the radiolabeled antibody when givenat the maximum tolerated dose produces a high response rate withmany responses of long duration, but stressed that further follow-upis needed to determine response durability and long-term toxicity.