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Keywords:

  • chronic lymphocytic leukemia;
  • small lymphocytic lymphoma;
  • treatment;
  • ofatumumab;
  • rituximab;
  • pentostatin;
  • fludarabine;
  • chemoimmunotherapy

BACKGROUND

Although rituximab-based chemoimmunotherapy (CIT) has substantially improved clinical outcomes in chronic lymphocytic leukemia (CLL), only 40% to 50% of patients achieve a complete remission (CR). There remains interest in identifying new approaches to improve the effectiveness of CIT. Ofatumumab is a fully human anti-CD20 monoclonal antibody with greater apparent single-agent activity than rituximab in CLL patients.

METHODS

Previously untreated CLL patients in need of therapy received 6 cycles of CIT induction with pentostatin, cyclophosphamide, and ofatumumab (PCO) followed by response assessment.

RESULTS

Of the 48 patients enrolled, 77% completed PCO induction. Adverse events during induction included grade 3+ hematologic toxicity (27%) and grade 3+ nonhematologic toxicity (23%). Median CD4 count after induction and 6 months later were 186 × 106/L and 272 × 106/L. The overall response rate was 96% (46 of 48 patients), and the CR rate was 46% (22 of 48 patients). Among the 38 patients who underwent minimal residual disease evaluation, 7 (18%) were negative for minimal residual disease. After median follow-up of 24 months, 10 (21%) patients have progressed and 8 (17%) have required retreatment. The efficacy and toxicity of ofatumumab-based CIT compare favorably to our historical trials of rituximab-based CIT using an identical chemotherapy backbone (n = 64). Time to retreatment also appeared longer for ofatumumab-based CIT (free of retreatment at 24 months: 86% [95% confidence interval = 75-99] versus 68% [95% confidence interval = 56-81] for rituximab-based CIT).

CONCLUSIONS

Ofatumumab-based CIT is well tolerated in patients with previously untreated CLL. The efficacy of ofatumumab-based CIT compares favorably to historical trials of rituximab-based CIT, suggesting randomized trials comparing ofatumumab-based CIT and rituximab-based CIT should be considered. Cancer 2013;119:3788–3796. © 2013 American Cancer Society.