Colocci, Natalia

BACKGROUNDIn an ECOG‐ACRIN Cancer Research Group study (E1496), maintenance rituximab (MR) was reported to prolong progression‐free survival (PFS) in comparison with observation (OBS) alone in patients with indolent lymphoma after induction chemotherapy. Here the long‐term follow‐up of the same patient cohort is presented.METHODSPatients with indolent lymphoma received induction chemotherapy with cyclophosphamide, vincristine, and prednisone (CVP). Patients with stable disease or a better response were then randomized to weekly rituximab (375 mg/m2 × 4 doses) every 6 months for 2 years (MR) or to OBS. The primary endpoint was PFS; the secondary endpoints were overall survival (OS), response rate, and toxicities.RESULTSOf the 387 patients who initially received CVP induction, 158 were randomized to MR, and 153 were randomized to OBS. After a median follow‐up of 11.5 years, patients on MR had longer median PFS (4.8 years) than patients on OBS (1.3 years; hazard ratio [HR], 0.49; P < .0001). However, there was no difference in OS between MR and OBS (10‐year OS, 67% vs 59%; median OS, 13.5 years vs not reached; HR, 0.91; P = .69). Other than MR, only minimal residual disease after induction therapy was significantly associated with PFS on multivariate analysis (HR, 0.71; P = .02). A low initial tumor burden, minimal residual disease, follicular histology, a low Follicular Lymphoma International Prognostic Index score, and female sex were associated with longer OS. There was no increase in the rate of second primary malignancies with MR vs OBS.CONCLUSIONSWith long‐term follow‐up, MR did not influence OS. The PFS benefit was maintained. MR should be considered optional for patients with indolent B‐cell lymphoma. Cancer 2016;122:2996‐3004. © 2016 American Cancer Society.

Purpose To determine if maintenance rituximab (MR) after standard chemotherapy improves progression-free survival (PFS) in advanced-stage indolent lymphoma. Patients and Methods Patients with stage III-IV indolent lymphoma with responding or stable disease after cyclophosphamide, vincristine, and prednisone (CVP) chemotherapy were stratified by initial tumor burden, residual disease after CVP (minimal or gross), and histology, and randomly assigned to observation (OBS) or MR 375 mg/m2 once per week for 4 weeks every 6 months for 2 years. PFS was the primary end point. Results Three hundred eleven (282 with follicular lymphoma) evaluable patients who received CVP were randomly assigned to OBS (n = 158) or MR (n = 153). Best response improved in 22% MR versus 7% OBS patients (P = .00006). Toxicity was minimal in both study arms. Three-year PFS after random assignment was 68% MR versus 33% OBS (hazard ratio [HR] = 0.4; P = 4.4 × 10−10 [all patients]) and 64% MR v 33% OBS (HR = 0.4; P = 9.2 × 10−8 [patients with follicular lymphoma]). There was an advantage for MR regardless of Follicular Lymphoma International Prognostic Index score, tumor burden, residual disease, or histology. In multivariate analysis of MR patients, minimal disease after CVP was a favorable prognostic factor. OS at 3 years was 92% MR versus 86% OBS (HR = 0.6; log-rank one-sided P = .05) and, among patients with follicular lymphoma, OS was 91% MR versus 86% (HR = 0.6; log-rank one-sided P = .08). A trend favoring MR was observed among patients with high tumor burden (log-rank one-sided P = .03). Conclusion The E1496 study provides the first phase III data in untreated indolent lymphoma that MR after chemotherapy significantly prolongs PFS.