Rituximab and CHOP induction therapy for newly diagnosed mantle-cell lymphoma: molecular complete responses are not predictive of progression-free survival.

PURPOSE: To evaluate the efficacy of rituximab and cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) induction therapy in patients with newly diagnosed mantle-cell lymphoma (MCL). PATIENTS AND METHODS: From March 1997 to May 1999, 40 previously untreated patients with stage II through IV MCL were treated with six cycles of rituximab and CHOP chemotherapy in a phase II trial. Pretreatment and interval peripheral-blood (PB) and bone marrow (BM) specimens were also analyzed by polymerase chain reaction (PCR) for tumor-specific BCL-1/immunoglobulin H (IgH) translocations and clonal IgH rearrangements. Study end points included clinical and molecular response rates and long-term progression-free survival (PFS).
RESULTS: Forty-eight percent of patients achieved a complete response (CR)/CR unconfirmed (CRu), and 48% of patients obtained a partial response (PR). However, 28 of the 40 patients have already relapsed or developed progressive disease with a median PFS of 16.6 months. Twenty-five patients had PCR-detectable BCL-1/IgH or clonal IgH products in PB or BM at diagnosis. Nine of the 25 informative patients had no evidence of PCR-detectable disease in PB or BM after rituximab and CHOP therapy. However, patients who achieved molecular remissions in PB or BM had PFS similar to patients without molecular remissions (16.5 v 18.8 months, P =.51).
CONCLUSION: Favorable clinical and molecular response rates associated with rituximab and CHOP chemotherapy do not translate into prolonged PFS in MCL. Nevertheless, rituximab and combination chemotherapy may transiently clear PB or BM of detectable tumor cells, prompting additional consideration of antibody-based in vivo purging in subsequent clinical trials.