Randomized Phase III Trial of ¹³¹iodine-Tositumomab (Bexxar)/Carmustine, Etoposide, Cytarabine, Melphalan (BEAM) Vs. Rituximab/BEAM and Autologous Stem Cell Transplantation for Relapsed Diffuse Large B-Cell Lymphoma (DLBCL): No Difference in Progression-Free (PFS) or Overall Survival (OS)

To compare ¹³¹Iodine-Tositumomab/BEAM to Rituximab/BEAM as the conditioning regimen followed by autologous stem cell transplantation for patients with relapsed chemotherapy sensitive DLBCL.

The Blood and Marrow Transplant Clinical Trials Network (BMT CTN 0401) study sponsored by the National Heart, Lung, and Blood Institute and the National Cancer Institute enrolled 224 patients between 1/06 and 7/09. Eligible patients were age 18–80 years, had a Karnofsky performance score > 70%, persistent or recurrent DLBCL, chemotherapy sensitive disease, and had received 1–3 prior chemotherapy regimens. Patients with transformed DLBCL were excluded. Patients were randomized to receive ¹³¹Iodine Tositumomab (dosimetric dose of 5 mCi on day −19 and therapeutic dose of 75 cGy on day −12), carmustine 300 mg/m² (day −6), etoposide 100 mg/m² twice daily × 4 (days −5 to −2), cytarabine 100 mg/m² twice daily × 4 (days −5 to −2), and melphalan 140 mg/m² (day −1) (Bexxar/BEAM, n=111) vs. rituximab 375 mg/m² on days −19 and −12 with the BEAM regimen (R/BEAM, n=113). All drugs were given intravenously. The median age at the time of transplant was 56.8 years in the Bexxar/BEAM and 58.8 years in the R/BEAM arm. All 224 patients were included in the intent to treat analysis for the primary endpoint of 2-year PFS. Twelve patients were not transplanted and two patients were ineligible based upon incorrect pathologic subtype and therefore were not included in further analyses

The median follow-up of the patients was 25.5 months (mo) (range 13.8– 47.0) in the Bexxar/ BEAM and 24.7 mos (range 4.7 – 58.6) in the R/BEAM arms, respectively. The primary end point of 2-year PFS was 47.9% (95% CI: 38.2%, 57.0%) for Bexxar/BEAM and 48.6% (95% CI: 38.6%, 57.8%) for R/BEAM (p= 0.94). The 2-year OS of all randomized patients was 61.0% (95% CI: 50.9%, 69.6%) for Bexxar/BEAM and 65.6% (95% CI: 55.3%, 74.1%) for R/BEAM (p= 0.38). Patients in complete remission after salvage chemotherapy (CR2) had an improved 2-yr OS compared to patients with primary induction failure (PIF) or chemosensitive relapse (p= 0.005). However, there were no differences in any group by treatment arm. 2-yr OS for CR2 patients with Bexxar/BEAM was 76.9% (95% CI: 62.9%, 86.1%) compared to 79.9% (95% CI: 64.7%, 89.1%) with R/BEAM (p= 0.61). The most common cause of failure was progression/relapse of the lymphoma with a cumulative incidence of relapse/progression at 2 yrs post transplant of 45.0% (95% CI: 35.2%, 54.8%) in the Bexxar/BEAM arm and 48.1% (95% CI: 38.1%, 58.1%) in the R/BEAM arm (p= 0.69). The treatment related mortality was 4.9% (95% CI: 0.8%, 9.0%) in the Bexxar/BEAM and 4.1% (95% CI: 0.2%, 8.0%) in the R/BEAM arms at 2 years post transplant (p= 0.97). Engraftment was similar with neutrophils to > 500/ul in 96.1% (95% CI: 92.2%, 100%) of Bexxar/BEAM and 93.5% (95% CI: 88.6%, 98.4%) of R/BEAM patients by day +28 (p= 0.40). Platelet recovery to > 20,000/ul with no transfusion by day +100 was present in 84.5% (95% CI: 77.4%, 91.6%) of the Bexxar/BEAM and 81.3% (95% CI: 73.9%, 88.7%) of the R/BEAM patients (p= 0.58). The median maximum mucositis score (by OMAS scale) was higher in the Bexxar/BEAM patients at 0.72 compared to 0.31 in the R/BEAM patients (p < 0.0001). One case of myelodysplastic syndrome (MDS) was reported in each arm of the trial and one additional case of acute myelogenous leukemia (AML) was reported in the R/BEAM arm. By exploratory analyses, immune reconstitution as measured by levels of quantitative immunoglobulins and B and T-lymphocyte subsets was not different between the two randomized arms at baseline, day +100, day +365, or day +730.

The Bexxar/BEAM and the R/BEAM regimens produced similar 2-yr PFS and OS for patients with chemotherapy sensitive relapsed DLBCL. No differences in engraftment or other toxicities were apparent other than an increase in mucositis with the Bexxar/BEAM regimen. No significant difference in the risk of MDS or AML could be detected with the current follow up.

Vose:Genentech: Research Funding; Pharmacyclics: Research Funding; SBio: Research Funding; Exelixis: Research Funding; BMS: Research Funding; Celgene: Research Funding; Millenium: Research Funding; GSK: Research Funding. Off Label Use: 131 Iodine Tositumomab combined with BEAM chemotherapy as a transplant preparative regimen for diffuse large B-cell lymphoma is an off label use. Burns:Novartis: Research Funding. Press:Roche/Genentech: Consultancy, Honoraria; Spectrum: Consultancy, Honoraria. Fenske:Seattle Genetics: Consultancy, Honoraria; Spectrum Pharmaceuticals: Consultancy, Honoraria; Millennium (Takeda) Pharmaceuticals: Research Funding.