In vivo depletion of B cells using a combination of high-dose cytosine arabinoside/mitoxantrone and rituximab for autografting in patients with non-Hodgkin's lymphoma

We performed a pilot study including rituximab (Mabthera; IDEC-C2B8, Hoffma nn-La Roche) with a sequential high-dose therapy protocol in 15 patients wi th follicular and three patients with mantle cell lymphoma and studied the potential of the chemoimmunotherapy to induce depletion of malignant B cell s in vivo. Our treatment protocol included induction with three cycles of C HOP (cyclophosphamide, doxorubicin, vincristine and prednisone) chemotherap y, followed by peripheral blood stem cell (PBSC) mobilization using high-do se cytosine arabinoside (2 g/m(2) every 12 h, days 1 and 2) and mitoxantron e (10 mg/m(2), days 2 and 3) (HAM), preceeded by rituximab (375 mg/m(2)). T he proportion of CD19(+) B cells in blood and bone marrow decreased from 1. 2 +/- 0.4% to 0.13 +/- 0.1% (P = 0.01) and from 2.7 +/- 0.8% to 0.8 +/- 0.5 % (P = 0.03) respectively. The number of t(14;18)-positive cells in blood a nd bone marrow progressively decreased with treatment, as assessed by the q uantitative real-time PCR assay in four patients. Conversion to PCR-negativ ity was achieved in the peripheral blood (PB) of seven informative patients . Leucaphereses were performed during the granulocyte colony-stimulating fa ctor (G-CSF)-supported leucocyte recovery phase. In 17 of 18 patients, a me dian of 15.1 x 10(6) CD34(+) cells/kg body weight (BW) could be harvested b y a single procedure for enrichment by an immunomagnetic method. Leucaphere sis products contained 51.3 +/- 28.8 x 10(4) CD19(+) B cells/kg BW (mean) a nd were t(14;18) PCR negative in all seven informative patients. These data compare favourably with results obtained in patients treated with the same regimen without rituximab. The high-dose therapy (n = 12 patients), includ ing total body irradiation (14.4 Gy) and cyclophosphamide (200 mg/kg BW), w as also preceeded by rituximab. Recovery of neutrophils to > 0.5 x 10(9)/l and of platelets to > 20 x 10(9)/l required a median of 13.5 and 11.5 d (ra nge 11-24 and 9-24 d) respectively. In conclusion, the addition of the CD20 antibody to chemotherapy ensured tumour depletion in vivo and allowed the collection of PBSCs devoid of tumour cells and with conserved engraftment c apability.