Primary Rituximab and Maintenance

Study medication * First period: Induction of response with 8 x rituximab combined with 8 cycles of CVP or 6 cycles of CHOP in 21-day cycles or 6 cycles of FCM in 28-day cycles or 6 cycles of MCP in 28-day cycles. * Second period: rituximab 375 mg/m2 every 8 weeks for 24 months (12 injections) or control with no treatment