Engraftment and molecular monitoring of CD34+ peripheral-blood stem-cell transplants for follicular lymphoma: a pilot study.

Abstract

A pilot study to validate the use of CD34+ selection (Ceprate SC) of blood stem-cell collection in patients with advanced follicular lymphoma receiving myeloablative chemoradiotherapy. Seventeen patients were entered onto the protocol. Thirteen of 17 patients have undergone transplantation; the median age is 42.5 years (range, 33 to 51), seven of 13 are stage IVB, two stage IVA, three stage IIIB, and one stage IIB. All except two patients were treated after first or subsequent relapses after receiving cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) chemotherapy to achieve a good partial (six of 13) or complete (seven of 13) response before stem-cell mobilization with cyclophosphamide 3 g/m2 and filgrastim 300 microg once daily. Eleven of 13 patients had a detectable t(14;18) by nested polymerase chain reaction (PCR). Median CD34+ count before selection was 2.9 x 10(6)/kg (range, 1.17 to 11.3) and after CD34+ selection was 1.54 x 10(6)/kg (range, 0.88 to 7.6) with a median CD34+ yield of 62.4% (range, 17% to 95%) and purity of 60% (range, 39.3% to 73%). Of the 11 patients known to have t(14;18), 10 had PCR-detectable contamination of stem-cell harvests that became PCR negative in six of the 10 after CD34+ selection. Engraftment was rapid with a median day to absolute neutrophil count (ANC) greater than 0.5 x 10(9)/L of 13 days (range, 11 to 21) and platelet count greater than 20 x 10(9)/L of 14 days (range, 10 to 44). With a median follow-up duration of 15 months, three patients have remained persistently PCR-positive, two of whom received PCR-positive stem cells. Two have relapsed. Of the seven patients who received PCR-negative stem cells, five have had no PCR-detectable disease in posttransplant bone marrow samples. Longer follow-up duration is required to determine the significance of these findings, but we have confirmed the feasibility of CD34+ selected cells to deplete peripheral-blood stem cells of tumor cells from patients undergoing high-dose therapy for follicular lymphoma.