A phase III randomized intergroup trial (S0016) comparing CHOP plus rituximab with CHOP plus iodine-131-tositumomab for front-line treatment of follicular lymphoma: Results of subset analyses and a comparison of prognostic models.

Abstract

8001 Background: Advanced follicular lymphomas (FL) are considered incurable with chemotherapy and there is no consensus on the best treatment. Outcomes are variable, but can be partially predicted by defined prognostic factors. SWOG and CALGB compared the safety and efficacy of 2 immunochemotherapy regimens in a Phase III trial enrolling 554 patients between 3/1/2001 and 9/15/2008. Methods: Patients were eligible if they had bulky stage II, III or IV FL and had not received prior therapy. Patients randomized to CHOP-R received 6 cycles of CHOP every 21 days + 6 doses of rituximab. Patients randomized to CHOP-RIT received 6 cycles of CHOP, followed by consolidative radioimmunotherapy with tositumomab/iodine I-131 tositumomab. A Cox proportional hazards multi-variable regression analysis assessed the prognostic impact of age, stage, LDH, LN size and number, performance status, hemoglobin, β2 microglobulin, BM involvement, and B symptoms. The prognostic value of 3 multi-variable models were compared. Results: Outcomes were outstanding with either CHOP-R or CHOP-RIT (2 yr PFS: 76% vs 80% [ p =0.11]; 2 yr OS: 97% vs 93% [p =0.08], respectively). Subset analyses so far have not identified any subgroups clearly benefitting to a greater degree from CHOP-R or CHOP-RIT in terms of both PFS and OS. Cox multivariable regression analysis identified serum-β2M, LDH level, and FLIPI index as the strongest prognostic factors associated with worse PFS and OS. Conclusions: Both regimens produced outstanding PFS and OS, and no statistically significant differences between them were observed. FLIPI, FLIPI2, and LDH + β2M models were all strong predictors of patient outcomes. A combination of LDH + β2M was as good as the FLIPI index, and was simpler to apply. (Supported in part by NCI grants CA32102 and CA38926 from the NCI and GlaxoSmithKline.) [Table: see text]