Mobilization of peripheral blood progenitor cells with vinorelbine and granulocyte colony-stimulating factor in multiple myeloma patients is reliable and cost effective

Daratumumab during Myeloma Induction Therapy Is Associated with Impaired Stem Cell Mobilization and Prolonged Post-Transplant Hematologic Recovery

Daratumumab is being increasingly integrated into first-line multiple myeloma (MM) induction regimens, leading to improved response depth and longer progression-free survival. Autologous stem cell transplantation (ASCT) is commonly performed as a consolidation strategy following first-line induction in fit MM patients. We investigated a cohort of 155 MM patients who received ASCT after first-line induction with or without daratumumab (RVd, n = 110; D-RVd, n = 45), analyzing differences in stem cell mobilization, apheresis, and engraftment. In the D-RVd group, fewer patients successfully completed mobilization at the planned apheresis date (44% vs. 71%, p = 0.0029), and more patients required the use of rescue plerixafor (38% vs. 28%, p = 0.3052). The median count of peripheral CD34+ cells at apheresis was lower (41.37 vs. 52.19 × 106/L, p = 0.0233), and the total number of collected CD34+ cells was inferior (8.27 vs. 10.22 × 106/kg BW, p = 0.0139). The time to recovery of neutrophils and platelets was prolonged (12 vs. 11 days, p = 0.0164; and 16 vs. 14 days, p = 0.0002, respectively), and a higher frequency of erythrocyte transfusions (74% vs. 51%, p = 0.0103) and a higher number of platelet concentrates/patients were required (4 vs. 2; p = 0.001). The use of daratumumab during MM induction might negatively impact stem cell mobilization and engraftment in the context of ASCT.

A new protocol for improving efficiency of autologous peripheral blood stem cell collection in patients with high white blood cell counts

BACKGROUND

Collection efficiency (CE) of peripheral blood stem cell (PBSC) collections is negatively affected by increasing white blood cell (WBC) counts of the patient. This study compared a new optimized mononuclear cell (MNC) collection protocol (OPP) to the standard MNC collection protocol recommended by the manufacturer (STP) for PBSC collection in patients with WBC counts >35 000/μL.

STUDY DESIGN AND METHODS

Single-center, retrospective, and observational study of 81 autologous PBSC collections on Fenwal Amicus cell separators in 70 adult patients.

RESULTS

Median peripheral WBC count (×10³ /μL; 44.2 in OPP group vs 46.5 in STP group) and median CD34⁺ count (105/μL in OPP group vs 40/μL in STP group) at the beginning of PBSC collection did not differ significantly. Median CE2 (45% vs 31%; P < .001) as well as CD34⁺ yield of the apheresis product both with regards to median absolute CD34⁺ content (×10⁶ ; 793 vs 188; P = .001) as well as median CD34⁺ content (×10⁶ )/kg body weight (8.93 vs 2.51; P = .002) were significantly higher for the OPP. Overall, 18/21 (86%) patients with the OPP obtained their target CD34⁺ amount with a single apheresis session, compared to 25/50 (50%) with the STP (P = .005). PBSC collections using OPP lasted significantly longer (median 377 minutes vs 260 minutes; P < .001) than with the STP.

CONCLUSIONS

The OPP significantly improves CE2 for PBSC collections on Fenwal Amicus cell separators in patients with pre-apheresis WBC counts >35 000/μL and significantly reduces the necessity for multiple apheresis sessions. The OPP is therefore suited to reduce both patient burden and cost in autologous PBSC collection.

Autologous Transplantation for Older Adults with AML

While the majority of patients with acute myeloid leukemia (AML) are above the age of 65 years at diagnosis, the outcome of older AML patients remains disappointing. Even if standard intensive chemotherapy induces morphologic complete remission (CR1), relapses in older AML patients are common leading to poor long-term survival outcomes. Since autologous hematopoietic stem cell transplantation (HCT) offers distinct anti-leukemic effectiveness while avoiding graft-versus-host disease associated with allogeneic transplantation, it represents an option for consolidation treatment in selected older AML patients. However, prospective studies in older AML patients assessing the benefit of autologous HCT compared to chemotherapy consolidation or allogeneic transplantation are lacking. Consequently, clinicians face the dilemma that there is considerable ambiguity on the most appropriate consolidation treatment for older AML patients in CR1. This review highlights the possible role of autologous HCT for consolidation in older AML patients reaching CR1 after induction treatment.

Vinorelbine-Cyclophosphamide compared to cyclophosphamide in peripheral blood stem cell mobilization for multiple myeloma

BACKGROUND

High dose Cyclophosphamide (Cy) and Vinorelbine Cyclophosphamide (Vino-Cy) are stem cell (SC) mobilisation options for patients with multiple myeloma (MM). We present a comparison of mobilisation outcomes using these regimens.

PATIENTS AND METHODS

Vino-Cy patients received Vinorelbine 25 mg/m² on day 1, cyclophosphamide 1500 mg/m² on day 2, and pegylated GCSF on day 4 or GCSF 10 mcg/kg/day from day 4 onwards. Cy patients were given cyclophosphamide 4000 mg/m² on day 1 and GCSF10 mcg/kg/day from day 5 onwards. The target CD34 + SC collection was 5 × 10⁶ per kg/BW.

RESULTS

149 patients were included. SC collection was lower in the Vino-Cy group (8.20 × 10⁶/Kg BW) compared to the Cy group (11.43 × 10⁶/Kg BW), with adjusted geometric mean ratio of 0.59 (95% CI 0.41 to 0.86, p = 0.006). Time taken to achieve an adequate PB SC count was shorter for Vino-Cy (9 ± 1 day compared to 12 ± 2 days for Cy, adjusted absolute mean difference -3.95, 95% CI -4.85 to -3.06, P < .001). Mobilisation related toxicities (in particular, neutropaenic fever) were greater for Cy.

CONCLUSION

Vino-Cy is a potential alternative to Cy given the need for effective mobilisation protocols with acceptable toxicity.

Mobilization of Hematopoietic Progenitor Cells with Standard- or Reduced-Dose Filgrastim after Vinorelbine in Multiple Myeloma Patients: A Randomized Prospective Single-Center Phase II Study

Vinorelbine combined with filgrastim at a dose of 10 µg/kg of body weight (BW) per day is a reliable and well-tolerated regimen for mobilization of hematopoietic progenitor cells (HPCs) in patients with multiple myeloma. This prospective, randomized, phase II study was initiated to assess the feasibility of a reduced filgrastim dosage. Vinorelbine was combined with either standard-dose filgrastim (10 µg/kg BW per day) or reduced-dose filgrastim (5 µg/kg BW per day). Leukapheresis sessions were planned to start at day 8 and were continued until the predefined target amount of 4 × 10⁶ HPCs/kg BW was collected. The study demonstrated the feasibility of vinorelbine combined with reduced daily filgrastim with a mean of 1.29 leukapheresis sessions necessary per patient (95% confidence interval, .95 to 1.7). All patients could start leukapheresis as planned at day 8, and the collection success rate was 100% for the whole patient collective after a maximum of 2 leukapheresis sessions. No statistically significant differences with regard to the amount of HPCs collected between the 2 groups were observed (P = .99). Accordingly, no differences were seen with regard to length of hospitalization for autotransplant (P = .34) and duration of neutrophil (P = .93) and platelet engraftment (P = .42). Patients receiving reduced-dose filgrastim reported significantly lower peak pain values in a numeric analogue scale (P = .01), and the costs were significantly lower than in patients undergoing standard-dose chemomobilization (P = .001). Vinorelbine 35 mg/m² plus filgrastim 5 µg/kg BW once per day until completion of HPC collection is feasible and appears to be advantageous with respect to the severity of pain intensity and treatment costs.

Mobilization of hematopoietic progenitor cells for autologous transportation: consensus recommendations

Selected patients with certain hematological malignancies and solid tumors have the potential to achieve long-term survival with autologous hematopoietic progenitor cell transplant. The collection of these cells in peripheral blood avoids multiple bone marrow aspirations, results in faster engraftment and allows treatment of patients with infection, fibrosis, or bone marrow hypocellularity. However, for the procedure to be successful, it is essential to mobilize a sufficient number of progenitor cells from the bone marrow into the blood circulation. Therefore, a group of Brazilian experts met in order to develop recommendations for mobilization strategies adapted to the reality of the Brazilian national health system, which could help minimize the risk of failure, reduce toxicity and improve the allocation of financial resources.

Successful hematopoietic stem cell mobilization with vinorelbine and filgrastim in germ cell tumor

Germ cell tumor (GCT) is the most frequent cancer in young men and is highly curable. Almost 80 % of patients with the disease in an advanced stage achieve a reliable response to cisplatin combination chemotherapy. For relapsing or refractory disease, autologous hematopoietic stem cell transplantation (HSCT) is an effective therapy. The two most used mobilization strategies for HSC collection are filgrastim alone or filgrastim after chemotherapy (chemomobilization). HSC collection with filgrastim mobilization can be difficult, especially in highly treated patients. While the addition of chemotherapy improves mobilization and reduces the number of apheresis sessions, it can increase morbidity rate as well. We describe a case of a 45-year-old male with classical seminoma who was submitted to orchiectomy. Two months after, he presented progression of the tumor. He received four cycles of cisplatin, etoposide and bleomycin, with residual retroperitoneal mass and cervical lymphadenopathy. Further, he was submitted to three more cycles of cisplatin, ifosfamide and paclitaxel. Thereupon, he showed partial response. At that moment, autologous HSC transplantation was considered. In the first mobilization, filgrastim alone was used without success in harvesting. The second mobilization consisted of vinorelbine at day 1 (35 mg/m²) and filgrastim (16 µg/kg) started at day 5. The peak of CD34+ cells in peripheral blood was 32.6 × 10⁶ cells/L on day 8, with 4.73 × 10⁶ cells/kg CD34+ collected on days 8 and 9. The benefits of this scheme include: (a) outpatient administration, (b) fewer doses of filgrastim, (c) minimal risk of febrile neutropenia and (d) reliable prediction of collection day. For these reasons, we conclude that vinorelbine chemomobilization is a great option for GCT, particularly in patients with high risk of mobilization failure. Furthermore, it requires less resource usage, hospitalizations and transfusions than conventional chemomobilization.

Efficacy of vinorelbine plus granulocyte colony-stimulation factor for CD34+ hematopoietic progenitor cell mobilization in patients with multiple myeloma

We aimed to assess the efficacy of vinorelbine plus granulocyte colony-stimulating factor (G-CSF) for chemo-mobilization of CD34(+) hematopoietic progenitor cells (HPC) in patients with multiple myeloma and to identify adverse risk factors for successful mobilization. Vinorelbine 35 mg/m(2) was administered intravenously on day 1 in an outpatient setting. Filgrastim 5 μg/kg body weight (BW) was given twice daily subcutaneously from day 4 until the end of the collection procedure. Leukapheresis was scheduled to start on day 8 and be performed for a maximum of 3 consecutive days until at least 4 × 10(6) CD34(+) cells per kg BW were collected. Overall, 223 patients were mobilized and 221 (99%) patients proceeded to leukapheresis. Three (1.5%) patients required an unscheduled hospitalization after chemo-mobilization because of neutropenic fever and renal failure (n = 1), severe bone pain (n = 1), and abdominal pain with constipation (n = 1). In 211 (95%) patients, the leukaphereses were started as planned at day 8, whereas in 8 (3%) patients the procedure was postponed to day 9 and in 2 (1%) patients to day 10. In the great majority of patients (77%), the predefined amount of HPC could be collected with 1 leukapheresis. Forty-four (20%) patients needed a second leukapheresis, whereas only 6 (3%) patients required a third leukapheresis procedure. The median number of CD34(+) cells collected was 6.56 × 10(6) (range, .18 to 25.9 × 10(6)) per kg BW at the first day of leukapheresis and 7.65 × 10(6) (range, .18 to 25.9 × 10(6)) per kg BW in total. HPC collection was successful in 212 (95%) patients after a maximum of 3 leukaphereses. Patient age (P = .02) and prior exposition to lenalidomide (P < .001) were independent risk factors for a lower HPC amount collected in multiple regression analysis. Vinorelbine plus G-CSF enables a very reliable prediction of the timing of leukapheresis and results in successful HPC collection in 95% of the patients.

High levels of circulating CD34+ cells at autologous stem cell collection are associated with favourable prognosis in multiple myeloma

Background:

High-dose chemotherapy with autologous stem cell transplantation is a cornerstone in the first-line treatment of multiple myeloma patients. However, only few factors have been identified affecting the outcome in such patients. We hypothesised that varying levels of mobilised CD34+ cells confer prognostic information in myeloma patients undergoing high-dose chemotherapy.

Methods:

We determined circulating CD34+ cells at the day of peripheral stem cell collection in 158 consecutive myeloma patients between January 2001 and August 2010. Patients were stratified into two groups (super vs normal mobilisers) with a cutoff of 100 000 peripheral CD34+ cells per ml.

Results:

We found that patients with more than 100 000 peripheral CD34+ cells per ml had a better overall survival (P=0.005) and a prolonged time to progression (P=0.0398) than patients with CD34+ cell counts below 100 000 CD34+ cells per ml. High levels of CD34+ cells were an independent marker for better overall survival and time to progression in a multivariate analysis that included disease stage, response at transplant, light-chain subtype, age, sex, and height.

Conclusion:

Our results suggest that high levels of mobilised peripheral CD34+ cells are associated with favourable outcome in myeloma patients undergoing autologous transplantation.

Assessing the charges associated with hematopoietic stem cell mobilization and remobilization in patients with lymphoma and multiple myeloma undergoing autologous hematopoietic peripheral blood stem cell transplantation

BACKGROUND

The purpose of this study was to perform a detailed analysis of the charges associated with chemomobilization and remobilization of autologous hematopoietic stem cells (HSCs) and to quantify medical costs and resource utilization associated with these procedures.

STUDY DESIGN AND METHODS

Patients with lymphoma underwent chemomobilization with ifosfamide and etoposide with or without rituximab (IE ± R). Patients with multiple myeloma (MM) received a modified hyperfractionated cyclophosphamide, vincristine, doxorubicin, dexamethasone (hyper-CVAD) regimen after failing to mobilize with growth factors only.

RESULTS

Between January 2004 and October 2006, 98 patients with lymphoma underwent HSC mobilization with IE ± R. Mobilization with IE ± R was effective, with 90.8% of patients collecting at least 2 × 10(6) CD34+ cells/kg. The total charges for treatment were $27,996 and $37,667 for patients mobilized with IE and IE + R, respectively. Hospital readmission for complications occurred in 26.5% of patients, resulting in additional charges of $10,356. The preapheresis procedure charge was estimated to be $2522, the charge for a 2-day apheresis session was $5160, and the postapheresis phase resulted in charges of $8040. Our analysis determined that reducing apheresis by 1 day has the potential to save $6600. We also performed a retrospective analysis of 16 patients with MM remobilized with a modified hyper-CVAD regimen. Remobilization was successful, with 87.5% of patients. Our analysis determined that mobilization, preapheresis, apheresis, and postapheresis phase charges were $24,968, $2522, $6158, and $12,060, respectively.

CONCLUSIONS

Optimization of HSC mobilization regimens to reduce failure rates would not only benefit patients but also reduce the overall medical costs.

Efficient mobilization of PBSC with vinorelbine/G-CSF in patients with malignant lymphoma

High-dose chemotherapy (HDT) and hematopoietic SCT are effective in patients with relapsing or refractory malignant lymphoma. Collection of sufficient numbers of stem cells is a prerequisite for such a therapy. In a pilot trial, we evaluated the feasibility of stem cell mobilization with vinorelbine/G-CSF in patients with lymphoma, a regimen allowing precise timing and harvesting of sufficient stem cells in myeloma patients. Forty-five patients with lymphoma received vinorelbine 35 mg/m(2) i.v. on day 1 and G-CSF 10 microg/kg/day s.c., divided in two daily doses from day 4 until collection. Stem cell collection was successfully performed in 43 patients (96%) with a median of 3.6 x 10(6) CD34(+) cells/kg (range: 1.4-16) in the collected product. In 28 patients (62%), the first stem cell apheresis was performed on day 8, and for 28 patients a sufficient stem cell yield was reached with one apheresis only. All 43 patients underwent high-dose chemotherapy with BEAM and auto-SCT with hematological recovery on time and without unexpected toxicity. In conclusion, vinorelbine/G-CSF allows accurate timing and safe harvesting of sufficient stem cells in patients with malignant lymphoma.

Multiple myeloma emerging after chemotherapy for non-small-cell lung cancer

A 67-year-old man underwent total resection of the left lung because of adenocarcinoma, with no evidence of extra-thoracic spread of the cancer. On follow-up, metastatic bone disease was documented and chemotherapy (CMT) which included cisplatin, docetaxel, vinorelbine, and topotecan was administered. Six months after completion of CMT, a rise in total serum protein was noted. Bone marrow biopsy revealed the diagnosis of an IgG lambda myeloma. We report a case of a man with adenocarcinoma of the lung who presented multiple myeloma after completion of chemotherapy.

Mobilization strategies for the collection of peripheral blood progenitor cells: Results from a pilot study of delayed addition G-CSF following chemotherapy and review of the literature

OBJECTIVE

Given the potential to limit cost, we conducted a pilot study evaluating delayed, low-dose granulocyte colony-stimulating factor (G-CSF) following chemotherapy for the procurement of peripheral blood progenitor cells (PBPCs) for autologous transplantation and reviewed the relevant literature.

PATIENTS AND METHODS

Twenty-eight patients with various malignancies received cyclophosphamide 4 gm/m(2) and paclitaxel 170 mg/m2 followed by G-CSF 300 microg/d or 480 microg/d starting day +5 until two to four daily large volume leukapheresis yielded > or =5.0 x 10(6) CD34+ cells. We searched MEDLINE, Pubmed, and EMBASE databases from 1990 to the present to identify papers on PBPC procurement using delayed G-CSF (starting day +4 or later) following chemotherapy.

RESULTS

G-CSF was administered for a median of 9 days at an average cost of 1260 USD per 70-kg patient. Collection was initiated at a median of 12 days after chemotherapy. A median 2.5 (range 2-4) apheresis were performed yielding an average daily CD34+ collection of 6.9 x 10(6)/kg (range 0.35-56.7). After one apheresis, 82% and 57% of patients collected > or =2.5 x 10(6)/kg and > or =5.0 x 10(6)/kg, respectively. Ultimately, 89% collected > or =5.0 x 10(6)/kg. Febrile neutropenia and catheter-related infection developed in five and two patients, respectively. All patients proceeded to transplantation and engrafted successfully with a median of 14.9 x 10(6)/kg (range 1.05-113) cells infused. Eleven published reports were identified involving 590 patients of whom 498 received G-CSF at a dose range of 250 microg/d to 10 microg/kg/d starting day +4 to 15 for a period of 4 to 9 days for PBPC procurement. Among these reports, 62 to 100% and 33 to 96% of patients collected > or =2 to 2.5 x 10(6) and > or =5.0 x 10(6) CD34+ cells, respectively.

CONCLUSION

The use of delayed, low-dose G-CSF plus chemotherapy for stem cell mobilization was feasible and provides further evidence supporting this potentially cost-effective strategy. A review of the literature supports our findings and emphasizes the need for larger studies to address this issue.

Hematopoietic cell transplantation for Crohn’s disease; is it time?

AIM: To review all studies in the literature that have assessed Hematopoietic cell transplantation (HCT) and Crohn’s disease (CD) with the ultimate aims of determining if this is a viable treatment option for those with CD. A secondary aim was to review the above literature and determine if the studies shed further light on the mechanisms involved in the pathogenesis of CD.

METHODS: An extensive Medline search was performed on all articles from 1970 to 2005 using the keywords; bone marrow transplant, stem cell, hematopoietic cell, Crohn’s disease and inflammatory bowel disease.

RESULTS: We identified one case in which a patient developed CD following an allogeneic HCT from a sibling suffering with CD. Evidence for transfer of the genetic predisposition to develop CD was also identified with report of a patient that developed severe CD following an allogeneic HCT. Following HCT it was found that the donor (that had no signs or symptoms of CD) and the recipient had several haplotype mismatches in HLA class III genes in the IBD3 locus including a polymorphism of NOD2/CARD15 that has been associated with CD. Thirty three published cases of patients with CD who underwent either autologous or allogeneic HCT were identified. At the time of publication 29 of these 33 patients were considered to be in remission. The median follow-up time was seven years, and twenty months for allogeneic and autologous HCT respectively. For patients who underwent HCT primarily for treatment of their CD there have been no mortalities related to transplant complications.

CONCLUSION: Overall these preliminary data suggest that both allogeneic and autologous HCT may be effective in inducing remission in refractory CD. This supports the hypothesis that the hemolymphatic cells play a key role in CD and that resetting of the immune system may be a critical approach in the management or cure of CD.

An update: Health economics of managing multiple myeloma

Based on Medline search, a summary is provided of recent health economic evidence in published literature relating to the management of multiple myeloma. The following major components of current multiple myeloma treatments are discussed: induction chemotherapy, high-dose chemotherapy supported by autologous peripheral stem cell transplantation (ASCT), long-term biphosphonates therapy to prevent skeletal events and recent advances for the treatment of relapsed or refractory multiple myeloma and under evaluation in primary treatment (thalidomide and bortezomib). Our study shows that there still appears to be a need for health economic information to confirm the cost-effectiveness of stem cell support versus high-dose chemotherapy without stem cell support, as well as to assess optimal biphosphonate treatment regimens. There is also a clear need for peer reviewed economic evaluations of novel therapies such as thalidomide and Bortezomib in the treatment of multiple myeloma at different stages of the disease.

Vinorelbine plus intermediate dose cyclophosphamide is an effective and safe regimen for the mobilization of peripheral blood stem cells in patients with multiple myeloma

High dose cyclophosphamide (HD-Cy) is commonly used to mobilize stem cells in multiple myeloma (MM). However, timing of collection is variable and incidence of side effects is substantial. We evaluated a combination of vinorelbine (VNB) (25 mg/m(2) day 1) plus Cy (1.5 g/m(2) day 2) and G-CSF as mobilizing regimen in 37 patients with MM. Results were compared to those achieved in 41 previously diagnosed patients mobilized with Cy at 4 g/m(2). Overall, 36/37 patients receiving VNB-Cy (97%) mobilized, as opposed to 40/41 (97%) in the controls (p:0.51). Median CD34+ cells peak was 94/mul for VNB-Cy patients and 96 for controls, p=0.36; median number of CD34+ cells collected was 9.2x10(6)/kg and 8.7x10(6)/kg, respectively (p=0.85). Median number of days to the highest CD34 count was shorter for VNB-Cy patients (nine vs 11, p=0.001). No VNB-Cy patient experienced grade 3-4 neutropenia and thrombocytopenia, as opposed to 63 and 19% in the controls (p=0.001 and 0.01, respectively). Hospitalization from toxicity was never required in VNB-Cy patients as compared to 19% in control group (p=0.01). We conclude that an outpatient combination of VNB plus intermediate dose Cy plus G-CSF is a safe, predictable, and highly effective mobilization regimen for patients with newly-diagnosed MM.

High-dose chemotherapy with autologous hematopoietic stem cell transplantation in patients with multiple myeloma

Multiple myeloma, for all practical purposes, remains an incurable malignancy; however, 5-year survival has improved substantially during the past 30 years. A major contribution to improved outcome is the use of high-dose chemotherapy and stem cell transplantation. This multifaceted approach to therapy requires an understanding of appropriate induction therapy, techniques for stem cell mobilization, appropriate conditioning and supportive care. Also of importance are prognosis, features that predict outcome, the suitability of transplant candidates, and post-transplantation maintenance therapy.

Cost of autologous peripheral blood stem cell transplantation: the Norwegian experience from a multicenter cost study

High-dose therapy with autologous blood progenitor cell support is now routinely used for patients with certain malignant lymphomas and multiple myeloma. We performed a prospective cost analysis of the mobilization, harvesting and cryopreservation phases and the high-dose therapy with stem cell reinfusion and hospitalization phases. In total, 40 consecutive patients were studied at four different university hospitals between 1999 and 2001. Data on direct costs were obtained on a daily basis. Data on indirect costs were allocated to the specific patient based on estimates of relevant department costs (ie the service department's costs), and by means of predefined allocation keys. All cost data were calculated at 2001 prices. The mean total costs for the two phases were US$ 32,160 (range US$ 19,092-50,550). The mean total length of hospital stay for two phases was 31 days (range 27-37). A large part of the actual cost in the harvest phase was attributed to stem cell mobilization, including growth factors, harvesting and cryopreservation. In the high-dose chemotherapy phase, the most significant part of the costs was nursing staff. Average total costs were considerably higher than actual DRG-based reimbursement from the government, indicating that the treatment of these patients was heavily subsidized by the basic hospital grants.

‘Agglutination and flocculation’ of stem cells collected by apheresis due to cryofibrinogen

Collection of peripheral stem cells by apheresis is a well-described process. Here, investigations concerning 'agglutination and flocculation' of stem cells collected from two patients are described. In both cases, cryoproteins were observed and cryofibrinogen was identified using high-resolution two-dimensional electrophoresis. In one case, peripheral stem cells were collected after a second course of mobilization, and the cells were immediately washed at 37 degrees C before being frozen, allowing their use, despite the presence of cryofibrinogen. In the other case, 'agglutination' was reversed by warming the bag, and plasma was removed before freezing.