Early Safety and Efficacy Analysis of a Phase II Study of Sequential R-CHOP and Yttrium-90 Ibritumomab Tiuxetan (Zevalin®) for Elderly High Risk Patients with Untreated DLBCL.

Introduction: Elderly patients (pts) with high risk DLBCL represent an increasing demographic, are often underserved in clinical trials, and need improved therapies. By the age-adjusted international prognostic index (aaIPI), pts >60 years (yrs) with high-intermediate (HI) and high risk (H) disease had 5 yr survival (OS) rates of 37%, and 21%, respectively. Rituximab’s addition to CHOP has improved responses and outcomes, but >50% of high risk pts still relapse. We are investigating the safety and efficacy of sequential RCHOP followed by Yttrium-90 ibritumomab tiuxetan (Zevalin ®) radioimmunotherapy (RIT) in an effort to improve these results. An early safety analysis of this sequential program is presented here.

Methods: Untreated ASCT-ineligible pts >60 yrs, with aaIPI HI or H risk DLBCL are eligible for study. Induction: pts receive R-CHOP chemotherapy at standard doses q 21 days x 6 cycles with prophylactic pegfilgrastim (or G-CSF) and darbepoetin alfa (Aranesp ®) support. Consolidation: pts with ≥ stable disease at post RCHOP restaging are eligible for ⁹⁰Y-90 ibritumomab tiuxetan, given 6–9 weeks post RCHOP; For platelet (plt) counts ≥ 150K → 0.4 mCi/kg dose, plt counts of 100–149K → 0.3 mCi/kg. Weekly CBC’s are performed until week 12–13 restaging.

Results: 26 pts have been enrolled as of July 12^th, 2005. Median age is 75 (range 65–85; male:female 9:17); KPS <80% in 55% (median 70%, range 60–90%); LDH > nl: 89% (range 150–804); Stage III/IV: 11.5% / 88.5 %; Extranodal sites are >1 in 50%; B symptoms in 54%; aaIPI HI (2 factors) = 46%, H (3 factors) = 54%; 18/26 pts have completed RCHOP; 8 pts are off study before RIT for: 4 cardiovascular events (1 CHF,1 Non-Q-wave MI, 1 sudden death, 1 V. Fib arrest), 3 neutropenic sepsis (1=grade 4, 2=grade 5), 1 leptomeningeal progression; 14 pts have received RIT. Median nadir counts during RIT occur at week 6–7: absolute neutrophil count (ANC) = 850 cells/mm3 (0.3–5.4), Hemoglobin (Hgb)= 10.1 gm/dl (6.6–14.6), plt = 28K cells/mm3 (7–103); Grade 3 and 4 ANC = 39%/39%, Hgb 39%/0%, Plt 46%/15%; During RIT, blood and Plt transfusion occurred for 46% and 31%, respectively; colony stimulating factor and erythropoietic support was used in 39% and 31%, respectively. One pt had delayed count recovery post RIT (448 days, transfusion independent from week 12→). Non-hematologic serious adverse events after RIT include: two grade 3 neutropenic infection (1 without fever), 1 grade 5 sudden death at week 7 (autopsy refused). OS and EFS for all pts by intent to treat is 60% and 55%, respectively, with 14 months median followup. Of pts post-RIT >12 weeks (11 pts), none have relapsed with 21 months median follow-up.

Conclusions: Treatment of elderly aaIPI HI and H risk DLBCL pts with sequential RCHOP followed by ⁹⁰Y ibritumomab tiuxetan is feasible and associated with manageable toxicity. Hematologic toxicity with RIT is similar to single agent toxicity, with slightly greater thrombocytopenia that warrants careful follow-up. Toxicity during RCHOP induction is significant in high risk elderly patients and cycle one modification is being implemented. Accrual continues to evaluate the potential long term impact of RIT on EFS and OS.