To evaluate the effect of rituximab in limited-stage diffuse large B-cell lymphoma (DLBCL), we conducted a multicenter phase II trial combining rituximab with three cycles of CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone; R-CHOP) followed by involved-field radiation therapy (IFRT).

Southwest Oncology Group (SWOG) study S0014 enrolled patients with newly diagnosed, aggressive, CD20-expressing non-Hodgkin's lymphoma (NHL). Patients had limited-stage disease and at least one adverse risk factor as defined by the stage-modified International Prognostic Index (nonbulky stage II disease, age > 60 years, WHO performance status of 2, or elevated serum lactate dehydrogenase). Four doses of rituximab were infused on days -7, 1, 22, and 43, and CHOP was administered on days 3, 24, and 45, followed 3 weeks later by 40 to 46 Gy of IFRT.

Sixty patients with aggressive NHL were eligible. With the median follow-up of 5.3 years, treatment resulted in a progression-free survival (PFS) of 93% at 2 years and 88% at 4 years. Overall survival (OS) was 95% at 2 years and 92% at 4 years. These results were compared with those from a historic group of patients treated without rituximab on S8736, demonstrating PFS of 78% and OS of 88% at 4 years.

In limited-stage DLBCL, the addition of rituximab to three cycles of CHOP plus IFRT met prespecified study criteria of efficacy, with 2-year PFS of at least 84%, meriting further investigation. There is a pattern of continuing relapse with modest survival gains. We hypothesize that such a pattern may be the result of biologic differences between limited- and advanced-stage lymphoma.