Phase II trial of short-course CHOP-R followed by 90Y-ibritumomab tiuxetan and extended rituximab in previously untreated follicular lymphoma

PURPOSE

Radioimmunotherapy has been approved for relapsed follicular lymphoma (FL), including rituximab-refractory FL. This study was designed to determine the CR rate with short-course chemoimmunotherapy with cyclophosphamide, doxorubicin, vincristine, prednisone, and rituximab (CHOP-R) followed by 90-Y ibritumomab tiuxetan (RIT) with extended rituximab as first-line treatment.

EXPERIMENTAL DESIGN

Between March 2004 and February 2007, 60 patients with stage II to IV symptomatic or bulky FL from a single institution supported by a large community network entered this phase II trial. Patients received CHOP-R for three treatment cycles before RIT followed by four additional weekly treatments with rituximab. Response was determined using fusion [(18) F] fluorodeoxyglucose-positron emission tomography (PET)-computed tomography (CT) imaging.

RESULTS

Of the 60 patients entering this trial, 55 patients completed all protocol therapy. The median follow up was 19.7 months (range, 0.26-35.9 months). For intent-to-treat analysis, the complete response (CR) rate after CHOP-R, as assessed by CT and PET imaging, was 40% and 46%, respectively. After RIT, the CR rate improved, as assessed by CT and PET imaging, to 82% and 89%, respectively. Ten patients have progressed, including eight from best response of CR. Seven of 18 patients who were PET positive after CHOP-R progressed compared with 3 of 37 patients who were PET negative (P=0.010).

CONCLUSIONS

In patients with previously untreated, symptomatic or bulky FL, short-course chemoimmunotherapy and consolidation RIT and extended rituximab resulted in a high CR rate. Failure to achieve an early PET CR after CHOP-R indicated high risk of relapse.

The expanding role of rituximab and radioimmunotherapy in the treatment of B-cell lymphomas

The role of rituximab in the treatment of B-cell lymphomas has rapidly emerged from the relapsed setting to first-line combination regimens across the broad range of histologic subtypes. The role of maintenance rituximab in indolent lymphomas after first-line therapy needs to be defined along with the integration of radioimmunotherapy into the first-line therapeutic regimens. As mechanisms of action/resistance to monoclonal antibody therapy are better understood, approaches to predicting response and optimizing combination therapy to overcoming primary and acquired resistance may be developed.