The Mobilisation of Peripheral Blood Stemcells in Patients with High Risk or Relapsed Non-Hodgkin Lymphoma Does Not Lead to the Presence of Detectable Tumour Cells in the Stem Cell Harvest.
Authors: de Greef Georgine E. , Broyl Annemiek , Kraan Jaco 
Published: October 2019

Abstract
Consolidation treatment with high dose chemotherapy in combination with an autologous peripheral blood stem celll transplant. is widely used in patients with high risk non-Hodgkin lymphoma (NHL). Also this treatment has its place in patients with relapsed intermediate lymphoma. Earlier studies in patients with breast cancer or multiple myeloma showed evidence for (minimal) tumour contamination in the graft that might lead to the occurence of relapse. For patients with NHL this is less clear. For the present analysis 60 patients (pts) were included: 18 pts with primary high risk NHL, 6 patients with mantle cell lymphoma, and 36 pts with primary refractory or relapsed intermediate NHL. Patients with high risk NHL were treated with induction chemotherapy according to the Hovon-27 or Hovon-40 protocol(www.hovon.nl). Two patients (1 pt with T-Lymphoblastair lymphoma, 1 pt with Burkitt Lymphoma ) received intensive induction chemotherapy according to our leukemia protocols. Stem cells were collected as early as possible, provided the peripheral blood and bone marrow showed no histological evidence of NHL and < 20% lymfocytes. In the patients with mantle cell lymphoma stem cells were collected during the induction chemotherapy (Hovon-45 protocol:www.hovon.nl), irrespective of their presence in the bone marrow. The patients with primary refractory or relapsed intermediate NHL received reinduction chemotherapy with DHAP (Dexamethason, Cytarabin, Cisplatin) or EMP (Etopside, Mitoxantrone, Prednisone). After two or three courses peripheral blood stem cells were mobilised with G-CSF (Neupogen, Amgen) 10 μg/kg sc daily starting day 5 and harvested for autologous stem cell transplant. Before the start of mobilisation patients were required to be responsive to the induction chemotherapy and to have a bone marrow without histological and immunological detectable tumour cells. In all patients a sample of the first day stem cell collection was analyzed with the use of three or four colour Flowcytometry. The sensitivity of the assay was 1/ 104–105 lymphoma cells. Only in 3 pts tumour cells were found at a level > 0.05 %. Interestingly two patients had a primary diagnosis of diffuse large B-cell lymphoma T-cell/ histiocyte rich variant. Both pts relapsed: one within 6 months and the other one within 12 months.The third patient suffered from a anaplastic large cell T-cell lymphoma and relapsed after 15 months. In all other patients no lymphoma cells were detectable in the stemcell harvest at a minimum level of <0.02%. Follow up showed a relapse within 12 months in 16 of 36 patients with relapse or primary refractory NHL (44%) and 6 of 24 patients with high risk NHL (25%). In conclusion, in the vast majority of the above patients, no circulating lymphoma cells were detectable with the use of flowcytometry in the stemcell harvest. Therefore we conclude that with the present techniques and sensitivity immunological analysis of the graft does not give additional information and therefore is not necessary in this patient group. Provided the bone marrow before collection is free of lymphoma cells, we feel that the currently used mobilisation regimen is safe in these patients and does not lead to the presence of detectable tumour cells in the collected stemcells.