Related Pediatric Donors – hematopoietic stem cell collection

The authors describe the collection of Hematopoietic stem cell and relevant aspects regarding donation for a minor donor

Impact of Induction Treatment on Stem Cell Collection: A COVID Related Study

Introduction: Standard induction therapy for multiple myeloma consists of 3-6 cycles of bortezomib, lenalidomide, and dexamethasone (VRd) or carfilzomib, lenalidomide and dexamethasone (KRd). Receiving greater than 6 cycles of a lenalidomide containing regimen is thought to negatively impact the ability to collect sufficient CD34+ stem cells for autologous stem cell transplant (Kumar, Dispenzieri et al. 2007, Bhutani, Zonder et al. 2013). Due to the COVID-19 pandemic, at least 20 patients at University of Maryland Greenebaum Comprehensive Cancer Center (UMGCC) had transplant postponed, potentially resulting in prolonged exposure to lenalidomide containing induction regimens. Here, in the context of modern stem cell mobilization methods, we describe a retrospective study that suggests prolonged induction does not inhibit adequate stem cell collection for transplant. Methods: By chart review, we identified 56 patients with multiple myeloma who received induction with VRd or KRd and underwent apheresis or stem cell transplant at UMGCC between 10/1/19 and 10/1/20. Patients were excluded if they received more than 2 cycles of a different induction regimen, had a past medical history of an inborn hematological disorder, or participated in a clinical trial of novel stem cell mobilization therapy. We defined 1 cycle of VRd or KRd as 1 cycle of "lenalidomide containing regimen". In accordance with routine clinical practice, we defined standard induction as having received 3-6 cycles of lenalidomide containing regimen and prolonged induction as having received 7 or more cycles. Results: 29 patients received standard induction (Standard induction cohort) and 27 received prolonged induction (Prolonged induction cohort) with lenalidomide containing regimens. The median number of cycles received by the Standard cohort was 6 (range 4-6), and the median number of cycles received by the Prolonged cohort was 8 (range 7-13). The frequency of KRd use was similar between patients who received standard induction and prolonged induction (27.58% vs. 25.93%, respectively). Standard induction and Prolonged induction cohorts were similar with respect to clinical characteristics (Fig 1), as well as the mobilization regimen used for stem cell collection (p = 0.6829). 55/56 patients collected sufficient stem cells for 1 transplant (≥ 4 x 10 6 CD34 cells/kg), and 40/56 patients collected sufficient cells for 2 transplants (≥ 8 x 10 6 CD34 cells/kg). There was no significant difference in the total CD34+ stem cells collected at completion of apheresis between standard and prolonged induction (10.41 and 10.45 x 10 6 CD34 cells/kg, respectively, p = 0.968, Fig 2). Furthermore, there was no significant correlation between the number of cycles of lenalidomide containing regimen a patient received and total CD34+ cells collected (R 2 = 0.0073, p = 0.5324). Although prolonged induction did not affect final stem yield, prolonged induction could increase the apheresis time required for adequate collection or result in more frequent need for plerixafor rescue. There was no significant difference in the total number of stem cells collected after day 1 of apheresis between patients who received standard or prolonged induction (8.72 vs. 7.96 x 10 6 cells/kg, respectively, p = 0.557). However, patients who received prolonged induction were more likely to require 2 days of apheresis (44% vs. 25%, p = 0.1625) and there was a trend toward significance in which patients who received prolonged induction underwent apheresis longer than patients who received standard induction (468 vs 382 minutes, respectively, p = 0.0928, Fig 3). In addition, longer apheresis time was associated with more cycles of lenalidomide containing regimen, which neared statistical significance (R 2 = 0.0624, p = 0.0658, Fig 4). There was no significant difference between standard and prolonged induction with respect to the frequency of plerixafor rescue. Conclusions: Prolonged induction with lenalidomide containing regimens does not impair adequate stem cell collection for autologous transplant. Prolonged induction may increase the apheresis time required to collect sufficient stem cells for transplant, but ultimately clinicians should be re-assured that extending induction when necessary is not likely to increase the risk of collection failure. Figure 1 Figure 1. Disclosures Badros: Janssen: Research Funding; J&J: Research Funding; BMS: Research Funding; GlaxoSmithKline: Research Funding.

Utilization of Stem Cell Transplantation in Newly Diagnosed Multiple Myeloma Patients Lacking Geographic Proximity to a Transplant Center

Introduction: Autologous stem cell transplant (ASCT) is considered standard of care in young and fit patients with newly diagnosed multiple myeloma. ASCT has shown to improve depth of response, progression free survival and overall survival compared to systemic therapy alone in myeloma patients (Harousseau et al. New England Journal of Medicine). Proximity to a stem cell transplant center may influence the utilization of this therapeutic option in transplant eligible multiple myeloma patients. Our cancer center did not have a stem cell transplant program in the 100-mile driving radius. The goal of this study was to assess the referral patterns and utilization of ASCT in newly diagnosed, young (age <65 years) multiple myeloma patients in a setting where patients are lacking proximity to a transplant center. Methods: The study was an IRB-approved retrospective cohort study. Patients between 18 and 65 years of age at the time of diagnosis who were diagnosed with multiple myeloma between January 1, 2014, and December 31, 2020, were included. Data including age at diagnosis, sex, race, zip code, treatment regimen, clinical data-including referral to a transplant center, stem cell collection and transplant-were collected and analyzed. Staging was calculated using lab values at the time of diagnosis or within 2 weeks of starting treatment. Date of diagnosis was defined as the date of bone marrow biopsy confirming systemic disease. All frequency and descriptive analyses were performed using SPSS Version 26 (Armonk, NY: IBM Corp.) Results: There were n = 62 patients that met the study inclusion criteria. Patients were mainly white (86%) and male (58%) with an average age at diagnosis of 55.9 (SD = 6.83) years. All patients (n = 62, 100%) lived at zip codes that were more than 100 miles from the closest transplant center. ISS staging showed 37% (n = 23, 95% CI 25% - 50%), 29% (n = 18, 95% CI 18% - 42%), and 18% (n = 11, 95% CI 9% - 30%) to have stage I, II, and III disease respectively. Twelve patients (n = 12, 19.4%, 95% CI 10.4% - 31.4%) had insufficient data for staging. The most common first line regimens were bortezomib, lenalidomide, and dexamethasone (n = 39, 62.9%, 95% CI 49.7% - 74.8%) and bortezomib, cyclophosphamide, and dexamethasone (n = 13, 21%, 95% CI 11.7% - 33.2%). Most patients (n = 48, 77.4%, 95% CI 65% - 87.1%) achieved a very good partial response or better. Eight (n = 8, 13%, 95% CI 5.7% - 23.9%) patients had refractory disease to first line therapy. Forty-six (n = 46, 74%, 95% CI 62% - 85%) patients were referred for HSCT evaluation, n = 16 (26%, 95% CI 15.5% - 38.5%) patients were not. Of the forty-six (n = 46) patients that were referred, n = 44 (96%, 95% CI 85% - 99.5%) patients had a clinical consultation with the transplant team. Of the entire cohort, n = 36 (58%, 95% CI 44.9% - 70.5%) patients underwent stem cell collection and n = 34 (55%, 95% CI 42% - 68%) patients underwent an ASCT after induction therapy. Conclusions: Our study found that more than one third of young patients with newly diagnosed multiple myeloma did not undergo stem cell collection or stem cell transplant. Lack of geographic access to a transplant center may be a contributing factor to the under utilization of this highly effective therapeutic strategy. Further investigation into interventions to improve ASCT referral and completion rates is imperative for improving outcomes for patients in such geographic locations. Disclosures Raj: Amgen: Membership on an entity's Board of Directors or advisory committees; Jazz pharmaceuticals: Speakers Bureau; Glaxo-Smith Kline: Speakers Bureau.

Prognostic Impact of CD3 Count in Apheresis Collection in Multiple Myeloma Patients Undergoing Autologous Stem Cell Transplant

Background: The use of immunotherapeutic agents in multiple myeloma (MM) has shown improvements in clinical outcomes, emphasizing the role the host immune system plays in disease control. In recognition of this relationship, efforts aimed at identifying biomarkers of immune surveillance in MM have identified prognostic value in the peripheral absolute lymphocyte (ALC) and absolute monocyte (AMC) counts at various stages of disease and following autologous stem cell transplant (ASCT), with lower ALC and AMC serving as a surrogate for immune dysregulation and correlating with inferior progression free (PFS) and overall survival (OS). With ASCT remaining the standard of care in the treatment of MM, we sought to examine whether CD3 content of the apheresis product during stem cell collection could be used as a biomarker for immune competence and whether it influences outcomes. Methods: A retrospective study was conducted on 1086 MM patients who underwent stem cell (CD34) collection with available CD3 data and subsequent ASCT at our institution. We recorded the total absolute CD3 and CD34 cell count upon completion of mobilization, with a higher CD3 count serving as a surrogate for immune competence. In addition to investigating the absolute CD3 count, we calculated the CD3/CD34 ratio given variation in the CD34 goals. Patients were dichotomized based on whether their absolute CD3 and CD3/CD34 ratio values were above or below medians. A Kaplan-Meier model was used to compare median PFS and OS between groups. A cox proportional hazards model was used to determine its prognostic impact, adjusting for ISS stage 3, high risk FISH, achievement of CR near day 100, and maintenance therapy received post-ASCT. Results: The median length of follow-up from date of ASCT for the entire cohort (N=1086) was 34.1 months (range: 0.26-157 months) and the median time from stem cell collection to ASCT was 9 days (range: 3-3143 days). The most common mobilizing regimen was Neupogen and plerixafor (N=425, 39%) and 694 (64%) patients received ASCT in the first line setting. The median absolute total CD3 count was 4.3 x 10^6/kg (range: 0.1-21.9) with 542 patients above and 544 patients at or below the median. The median absolute total CD34 count was 8.53 x 10^6/kg (range: 0.2-37.0) and median CD3/CD34 ratio was 0.50 (range: 0.01-15), with 536 patients above and 550 patients at or below the median ratio. The median PFS among patients with a CD3 count > 4.25 x 10^6/kg was 23.1 vs. 16.9 months among patients with CD3 count ≤ 4.25 x 10^6/kg (p<0.0001) and median OS was 65.3 months vs. 41.6 months (p<0.0001), respectively. A similar trend was observed when dividing patients based on CD3/CD34 ratio, with median PFS of 22.4 vs. 17.5 months (p=.0003) and median OS of 61.5 vs. 45.7 months (p=.0001), both favoring the cohort with a CD3/CD34 ratio > 0.5 (Figure 1). The prognostic value among patients with a CD3/CD34 ratio > 0.5 was retained after adjusting for ISS stage III, high risk FISH features, and use of maintenance therapy as follows: PFS HR: 0.73 (95% CI: 0.62-0.86; p=0.0002); OS 0.71 (95% CI: 0.59-0.88; p=0.001). Conclusions: Our study demonstrates that patients who have higher CD3 content in their apheresis product have better PFS and OS following ASCT. These findings reveal a possible role for using absolute CD3 and CD3/CD34 ratios in the apheresis product as a surrogate marker for immune competence and in predicting clinical outcomes. Figure 1 Figure 1. Disclosures Gertz: Akcea Therapeutics, Alnylam Pharmaceuticals Inc, Prothena: Consultancy; Akcea Therapeutics, Ambry Genetics, Amgen Inc, Celgene Corporation, Janssen Biotech Inc, Karyopharm Therapeutics, Pfizer Inc (to Institution), Sanofi Genzyme: Honoraria; Aurora Biopharma: Other: Stock option; AbbVie Inc, Celgene Corporation: Other: Data Safetly & Monitoring; Ionis Pharmaceuticals: Other: Advisory Board. Dingli: GSK: Consultancy; Sanofi: Consultancy; Janssen: Consultancy; Alexion: Consultancy; Apellis: Consultancy; Novartis: Research Funding. Dispenzieri: Takeda: Research Funding; Pfizer: Research Funding; Alnylam: Research Funding; Oncopeptides: Consultancy; Sorrento Therapeutics: Consultancy; Janssen: Consultancy, Research Funding. Kapoor: Sanofi: Research Funding; Takeda: Research Funding; Ichnos Sciences: Research Funding; Glaxo SmithKline: Research Funding; Regeneron Pharmaceuticals: Research Funding; AbbVie: Research Funding; Karyopharm: Research Funding; Karyopharm: Consultancy; Cellectar: Consultancy; BeiGene: Consultancy; Pharmacyclics: Consultancy; Sanofi: Consultancy; Amgen: Research Funding. Kumar: Novartis: Research Funding; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Antengene: Consultancy, Honoraria; Tenebio: Research Funding; Amgen: Consultancy, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bluebird Bio: Consultancy; BMS: Consultancy, Research Funding; Oncopeptides: Consultancy; Carsgen: Research Funding; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche-Genentech: Consultancy, Research Funding; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Research Funding; Astra-Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Beigene: Consultancy; Adaptive: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Research Funding.

A Phase II Study of Once Weekly Carfilzomib, Lenalidomide, Dexamethasone, and Isatuximab in Newly Diagnosed, Transplant-Eligible Multiple Myeloma

Background: Clinical data support the combination of a CD38 monoclonal antibody, an immunomodulatory drug, a proteasome inhibitor, and a glucocorticoid for the treatment of newly diagnosed multiple myeloma (NDMM). Recently, the GRIFFIN study evaluated the addition of the CD38 antibody, daratumumab to lenalidomide, bortezomib, and dexamethasone in transplant-eligible NDMM and demonstrated improved efficacy with an acceptable safety profile. Isatuximab is a newer CD38 monoclonal antibody that binds to a specific epitope of the CD38 receptor. In addition to antibody-dependent cellular cytotoxicity, antibody-dependent cellular phagocytosis, and complement-dependent cytotoxicity, isatuximab eliminates MM cells via direct apoptosis without the need for crosslinking. Isatuximab enhances immune function by boosting the activation and cytotoxic activity of natural killer cells and by depleting CD38+ immune suppressor cells such as regulatory T cells and inducing clonal expansion of T cells. Isatuximab is approved in combination with carfilzomib and dexamethasone for relapsed, refractory MM based on the results of the IKEMA study. The MANHATTAN study evaluated the 4-drug combination of daratumumab, lenalidomide, carfilzomib, and dexamethasone. The primary end point, minimal residual disease negativity was achieved in 29 of 41 patients (71%; 95% CI, 54%-83%). Building upon these data, our study evaluates the addition of isatuximab to weekly carfilzomib, lenalidomide, and dexamethasone. Study Design and Methods: A phase II, open-label clinical trial is being conducted to evaluate the efficacy of once weekly carfilzomib, lenalidomide, dexamethasone, and isatuximab (Isa-KRd) in 50 patients with newly diagnosed, transplant-eligible MM (NCT04430894). Eligible patients will have NDMM, age ≥18 years, ECOG PS of 0-2, and are deemed eligible for stem cell transplantation (SCT). All patients will receive 4 cycles of induction therapy with Isa-KRd followed by stem cell collection with the option to either proceed to upfront SCT versus deferred SCT. Patients undergoing upfront SCT will receive 4 cycles of therapy followed by stem cell collection, high-dose chemotherapy, and autologous SCT followed by 2 additional cycles of therapy then maintenance. Patients deferring SCT following collection will receive 4 cycles of therapy followed by stem cell collection followed by 4 additional cycles of therapy then maintenance. Each 28-day cycle will consist of isatuximab 10 mg/kg IV Q1 week for 8 weeks, then Q2 weeks for 16 weeks, thereafter Q4 weeks; carfilzomib (20 mg/m 2 Day 1 only) 56 mg/m 2 IV on Days 1, 8, 15; lenalidomide 25 mg po on Days 1-21; and dexamethasone 20 mg po day of and day after all doses of carfilzomib (Days 1, 2, 8, 9, 15, and 16) and isatuximab (Cycles 1 and 2 Days 22 and 23). For maintenance, patients will be stratified based on cytogenetics (high-risk cytogenetics include deletion (del) 17p, translocation t(4:14), t(14;16), t(14;20)). Patients with standard-risk cytogenetics will receive lenalidomide 10 mg po Days 1-21. Patients with high-risk cytogenetics will receive carfilzomib 56 mg/m 2 Days 1, 15; lenalidomide 10 mg po Days 1-21; and isatuximab 10 mg/kg IV Day 1. Dexamethasone, 20 mg orally or IV will be administered to patients as a pre-infusion medication prior to isatuximab dosing. Main Outcomes and Measures: The primary end point is complete response (CR + stringent CR) rate after 4 cycles of Isa-KRd as assessed by the International Myeloma Working Group (IMWG) Uniform Response Criteria. Secondary endpoints include determining safety and tolerability of Isa-KRd, minimal residual disease (MRD) after 4 cycles, at completion of consolidation (post-transplant) or induction (transplant-deferred), and sustained MRD at 24 months, progression-free survival, overall survival rates, and quality of life. Efficacy analysis will be performed both in the intent-to-treat (ITT) population and efficacy evaluable (EE) population. The ITT population will include all treated patients, and the EE population will include all patients who receive at least 1 cycle of study drug. The primary analysis will be based on the EE population, and will use the investigator-assessed response data evaluated according to consensus recommendations based on the IMWG criteria. CR (CR+sCR) rate after 4 cycles of Isa-KRd will be reported with 90% confidence interval. Support: Amgen and Sanofi Figure 1 Figure 1. Disclosures O'Donnell: Oncopeptide: Consultancy; Takeda: Consultancy; Janssen: Consultancy; Bristol Myer Squibb: Consultancy; Adaptive: Consultancy; Karyopharm: Consultancy. Mo: Janssen: Honoraria; GSK: Consultancy, Membership on an entity's Board of Directors or advisory committees; Epizyme: Consultancy; Karyopharm: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Eli Lilly: Consultancy; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees. Yee: Sanofi: Consultancy; Bristol Myers Squibb: Consultancy; Amgen: Consultancy; Oncopeptides: Consultancy; Adaptive: Consultancy; Janssen: Consultancy; GSK: Consultancy; Takeda: Consultancy; Karyopharm: Consultancy. Nadeem: GSK: Consultancy; Takeda: Consultancy; Karyopharm: Consultancy; Adaptive: Consultancy; Bristol Myer Squibb: Consultancy. Branagan: Sanofi-Genzyme: Consultancy, Membership on an entity's Board of Directors or advisory committees; BeiGene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Consultancy, Membership on an entity's Board of Directors or advisory committees; Adaptive: Consultancy; CSL Behring: Consultancy; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees. Rosenblatt: Parexel: Consultancy; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Imaging Endpoints: Consultancy; Attivare: Consultancy; Wolters Kluwer Health Inc: Consultancy, Patents & Royalties. Raje: Caribou: Other; Janssen: Other; bluebird bio: Other; Amgen: Other; Celgene: Other; BMS: Other. Richardson: AbbVie: Consultancy; GlaxoSmithKline: Consultancy; Secura Bio: Consultancy; Oncopeptides: Consultancy, Research Funding; Protocol Intelligence: Consultancy; Janssen: Consultancy; Karyopharm: Consultancy, Research Funding; Sanofi: Consultancy; Celgene/BMS: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; AstraZeneca: Consultancy; Regeneron: Consultancy; Jazz Pharmaceuticals: Consultancy, Research Funding.

Prophylactic Peripheral Blood Stem Cell Collection in Patients with Extensive Bone-Marrow Infiltration of Neuroendocrine Tumours Prior to Peptide Receptor Radionuclide Therapy with 177Lu-DOTATATE

Peptide receptor radionuclide therapy (PRRT) of metastatic neuroendocrine tumors (NET) can be successfully repeated but may eventually be dose-limited. Since 177Lu-DOTATATE dose limitation may come from hematological rather than renal function, hematological peripheral blood stem cell backup might be desirable. Here, we report our initial experience of peripheral blood stem-cell collection (PBSC) in patients with treatment-related cytopenia and therefore high risk of bone-marrow failure. Five patients with diffuse bone-marrow infiltration of NET and relevant myelosuppression (≥grade 2) received PBSC before one PRRT cycle with 177Lu-DOTATATE (7.6 ± 0.8 GBq/cycle). Standard stem-cell mobilization with Granulocyte-colony stimulating factor (G-CSF) was applied, and successful PBSC was defined as a collection of >2 × 106/kg CD34+ cells. In case of initial failure, Plerixafor was administered in addition to G-CSF prior to apheresis. PBSC was successfully performed in all patients with no adverse events. Median cumulative activity was 44.8 GBq (range, 21.3–62.4). Three patients had been previously treated with PRRT, two of which needed the addition of Plerixafor for stem-cell mobilization. Only one of five patients required autologous peripheral blood stem-cell transplantation during the median follow up time of 28 months. PBSC collection seems to be feasible in NET with bone-marrow involvement and might be worth considering as a backup strategy prior to PRRT, in order to overcome dose-limiting bone-marrow toxicity.

Single institution retrospective review of CD34+ apheresis collection based on mobilization regimen and primary diagnosis

Introduction/Objective Plerixafor has been increasingly used in conjunction with G-CSF to increase mobilization of CD34+ stem cells in patients undergoing leukapheresis collection for autologous stem cell transplantation. While G- CSF and plerixafor have been shown to increase CD34+ counts, studies examining patients’ ability to meet collection goals for patients with multiple myeloma (MM), diffuse large B-cell lymphoma (DLBCL), Hodgkin lymphoma (HL), and non-Hodgkin lymphoma (NHL) have not been well documented. Methods/Case Report All autologous stem cell collection patients between 2017-2021 were retrospectively reviewed and categorized by primary diagnosis. Patients received a mobilization regimen of G-CSF alone, G-CSF and plerixafor, G-CSF and chemotherapy, or G-CSF, plerixafor, and chemotherapy. CD34+ stem cell collection results were recorded. All units of CD34+ stem cells were processed according to protocol and viability was assessed by Trypan blue method on a thawed aliquot 2 weeks after processing. Results (if a Case Study enter NA) 385 patients (271 MM, 41 DLBCL, 30 HL, and 43 NHL patients; male: 242; female: 143; age range: 16-78) were identified. Binomial logistic regression demonstrated that use of plerixafor with G- CSF was negatively associated with meeting CD34+ goal collection (OR= -1.57, p= 0.003) compared to G-CSF alone. This result was particularly true for MM patients (OR= -1.62, p= 0.014). A pairwise t-test indicated that patients receiving G-CSF and plerixafor had lower CD34+ cell viabilities (t= 2.21, p = 0.028); after Bonferroni correction for multiple comparisons, MM samples also had significantly lower percentage viability than DLBCL (p= 0.003) or HL (p= 0.022) samples. Conclusion A higher percentage of patients mobilized on G-CSF alone were able to meet collection goal versus patients who were mobilized on G-CSF and plerixafor. Patients who received G-CSF and plerixafor had significantly lower viability than those who received G-CSF alone. We hypothesize these findings to be due to lower baseline mobilization for patients on G-CSF and plerixafor.

Study of Peripheral Mononuclear Cells and CD34 Levels as a Predictive Marker for Initiating Apheresis in Autologous Stem Cell Transplant

Background: Autologous HCT in multiple myeloma is done as upfront treatment in newly diagnosed transplant eligible patients after induction chemotherapy. In addition, it is standard for relapsed, aggressive non-Hodgkin lymphoma (NHL) and classical Hodgkin lymphoma (HL), and is curative in ~40% to 45% of patients. Over a decade, many efforts were made to find helpful parameters to predict an optimal time for initiating an efficient peripheral blood stem cell collection so that adequate stem cells are collected. It has been well accepted that CD34+ cell count in peripheral blood before leukapheresis is the best parameter to predict CD34 cell yield. However, white blood cell count, mononuclear cell count, and other easily obtained parameters are still used to guide the clinical practice of peripheral blood stem cell mobilization and collection. Materials and Methods: In the present study, we analyzed the correlation between peripheral blood MNC and Apheresis CD34 levels and also between peripheral blood CD34 by flow cytometry and apheresis CD34 levels. Results: We found that there was a statistically insignificant weak correlation between peripheral MNC and apheresis CD34. There was a statistically significant strong correlation between peripheral CD34 and apheresis CD34. Conclusion: The results show that peripheral blood MNC was analogous indicating that no reliable prediction can be done for CD34 cells collected in apheresis while peripheral CD34 by flow cytometry is the strongest predictor for initiating stem cell collection.

Prospective SPECT-CT Organ Dosimetry-Driven Radiation-Absorbed Dose Escalation Using the In-111 (111In)/Yttrium 90 (90Y) Ibritumomab Tiuxetan (Zevalin®) Theranostic Pair in Patients with Lymphoma at Myeloablative Dose Levels

Purpose: We prospectively evaluated the feasibility of SPECT-CT/planar organ dosimetry-based radiation dose escalation radioimmunotherapy in patients with recurrent non-Hodgkin’s lymphoma using the theranostic pair of 111In and 90Y anti-CD20 ibritumomab tiuxetan (Zevalin®) at myeloablative radiation-absorbed doses with autologous stem cell support. We also assessed acute non-hematopoietic toxicity and early tumor response in this two-center outpatient study. Methods: 24 patients with CD20-positive relapsed or refractory rituximab-sensitive, low-grade, mantle cell, or diffuse large-cell NHL, with normal organ function, platelet counts > 75,000/mm3, and <35% tumor involvement in the marrow were treated with Rituximab (375 mg/m2) weekly for 4 consecutive weeks, then one dose of cyclophosphamide 2.5 g/m2 with filgrastim 10 mcg/kg/day until stem cell collection. Of these, 18 patients with successful stem cell collection (at least 2 × 106 CD34 cells/kg) proceeded to RIT. A dosimetric administration of 111In ibritumomab tiuxetan (185 MBq) followed by five sequential quantitative planar and one SPECT/CT scan was used to determine predicted organ radiation-absorbed dose. Two weeks later, 90Y ibritumomab tiuxetan was administered in an outpatient setting at a cohort- and patient-specific predicted organ radiation-absorbed dose guided by a Continuous Response Assessment (CRM) methodology with the following cohorts for dose escalation: 14.8 MBq/kg, and targeted 18, 24, 28, and 30.5 Gy to the liver. Autologous stem cell infusion occurred when the estimated marrow radiation-absorbed dose rate was predicted to be <1 cGy/h. Feasibility, short-term toxicities, and tumor response were assessed. Results: Patient-specific hybrid SPECT/CT + planar organ dosimetry was feasible in all 18 cases and used to determine the patient-specific therapeutic dose and guide dose escalation (26.8 ± 7.3 MBq/kg (mean), 26.3 MBq/kg (median) of 90Y (range: 12.1–41.4 MBq/kg)) of ibritumomab tiuxetan that was required to deliver 10 Gy to the liver. Infused stem cells engrafted rapidly. The most common treatment-related toxicities were hematological and were reversible following stem cell infusion. No significant hepatotoxicity was seen. One patient died from probable treatment-related causes—pneumonia at day 27 post-transplant. One patient at dose level 18 Gy developed myelodysplastic syndrome (MDS), 4 patients required admission post-90Y RIT for febrile neutropenia, 16/18 patients receiving 90Y ibritumomab tiuxetan (89%) responded to the therapy, with 13 CR (72%) and 3/18 PR (17%), at 60 days post-treatment. Two patients had progressive disease at sixty days. One patient was lost to follow-up. Median time to progression was estimated to be at least 13 months. MTD to the liver is greater than 28 Gy, but the MTD was not reached as the study was terminated due to unexpected discontinuation of availability of the therapeutic agent. Conclusions: Patient-specific outpatient 90Y ibritumomab tiuxetan RIT with myeloablative doses of RIT up to a targeted 30.5 Gy to the liver is feasible, guided by prospective SPECT/CT + planar imaging with the theranostic pair of 111In and 90Y anti-CD20, with outpatient autologous stem cell transplant support. Administered activity over 5 times the standard FDA-approved activity was well-tolerated. The non-hematopoietic MTD in this study exceeds 28 Gy to the liver. Initial tumor responses were common at all dose levels. This study supports the feasibility of organ dosimetry-driven patient-specific dose escalation in the treatment of NHL with stem cell transplant and provides additional information on the radiation tolerance of the normal liver to radiopharmaceutical therapy.