Rituximab-PECC Induction Followed by ⁹⁰y-Ibritumomab Tiuxetan Consolidation in Relapsed or Refractory DLBCL Patients Who Are Not Eligible for or After ASCT: Preliminary Results From a Phase II HOVON Study.

Patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL) after- or not eligible for autologous stem cell transplantation (ASCT) have a poor prognosis. The optimum salvage therapy for these patients is not known. Treatment results with second-line chemotherapy have generally been disappointing. In some centers in the Netherlands PECC (Prednisone, Etoposide, Chlorambucil and Lomustine) combination chemotherapy is used as salvage treatment for such patients. PECC is a completely oral schedule. The efficacy and toxicity of PECC in this patient category has not been evaluated systematically before. ⁹⁰Y-ibritumomab tiuxetan (Zevalin^®) showed clinical activity as a single agent in relapsed DLBCL. We conducted a prospective multi-center phase II study evaluating induction therapy with Rituximab (R)-PECC followed in responsive patients by ⁹⁰Y-ibritumomab tiuxetan consolidation.

Patients aged ≥ 18 years with refractory CD20 positive DLBCL or first or second relapse, more than one year after or not eligible for ASCT, were enrolled. Treatment consisted of R-PECC (Prednisone 40 mg/m² po D1–5; Etoposide 100 mg/m² po D1–5; Chlorambucil 8 mg/m² po D1–5; Lomustine 80 mg/m² po D1 and Rituximab 375 mg/m² iv D1), every 28 days for 4 cycles. Patients with progressive disease after 2 cycles went off protocol. Patients in complete or partial remission after 4 cycles received consolidation treatment with ⁹⁰Y-ibritumomab tiuxetan at the standard single dose of 15 MBq/kg (0.4 mCi/kg) 6 to 12 weeks after start of the last R-PECC cycle. Response to treatment was evaluated according to the revised 2007 Cheson criteria.

Between November 2008 and February 2012 64 patients were enrolled. We report preliminary data for the first 50 patients evaluable for response and toxicity after the induction treatment with R-PECC. The median age was 70 years (range, 45–82) and median time since first diagnosis was 17 months (range 3–172). All patients had been treated with CHOP as first-line treatment and 8 patients (16%) had not been exposed to rituximab at first-line. Prior therapies consisted of (R)-CHOP (72%), R-CHOP and R-DHAP/VIM (16%) or R-CHOP and R-DHAP/VIM plus ASCT (12%). Eleven patients (22%) were refractory to their last prior systemic therapy. According to the secondary IPI, 26%, 28%, 34% and 8% of the patients belonged to the low-, low-intermediate-, high-intermediate-, and high risk group, respectively. Median relative dose intensities for the myelosuppressive agents of the PECC regimen were 93.7% (90% CI = 62.8–106.9%), 94.3% (90% CI = 71.6–104.7%) and 97.4% (90% CI 76.0–104.7%) for Lomustin, Etoposide and Chlorambucil, respectively. Progressive disease occurred in 14 patients (28%). Overall response rate (ORR) after induction treatment was 52%, including 34% complete response and 18% partial response. ORR of relapsed patients was significantly higher than that of patients refractory to their last prior treatment (64% vs. 9%, p=0.099). Patients more than one year from start of upfront treatment had a significant higher ORR than that of patients less than one year from start of upfront treatment (81% vs 21%, p=0.005). Median response duration was 13 months. One patient died because of treatment related toxicity due to sepsis and pneumonia after the first R-PECC cycle. The most common grade 3 or 4 adverse event was haematological toxicity (42%), followed by infection (14%), malaise (13%) and gastro-intestinal toxicity (6%). Eighteen serious adverse events (SAEs) occurred in 14 patients, 14 of the SAEs were possibly related to treatment (mainly hospitalisations because of infections). Approximately half of the patients (46%) have entered the ⁹⁰Y-ibritumomab tiuxetan consolidation phase of the study.

The R-PECC regimen shows good clinical activity in relapsed DLBCL patients. Its activity in refractory patients is low. This largely oral regimen provides patients not eligible for high-dose salvage treatment with a convenient treatment schedule with an acceptable safety profile.

Off Label Use: 90Y-ibritumomab tiuxetan is not registered for DLBCL.