Rituximab maintenance therapy typically involves multiple doses of rituximab given over a two-year period, such as at three-month intervals (for a total of eight doses in addition to whatever was given in initial treatment).
People who undergo rituximab maintenance have already responded to initial treatment. The premise behind the additional maintenance doses is that it may convert some partial responses into deeper (even complete) remissions, and that it should delay disease progression or relapse, since patients rarely relapse until at least after the maintenance round is complete.
The most important major clinical trial evidence supporting rituximab maintenance is an international study known as the PRIMA study (Primary Rituximab and Maintenance). PRIMA recruited over 1200 patients in 25 countries. 1019 people responded after initial treatment including rituximab (R-CHOP, R-CVP, or R-FCM) and then went on to the maintenance round. After three-years, progression-free survival was 75% in the maintenance arm, compared with 58% in the observation arm (who received no further treatment prior to progression).
Other studies have provided similar findings. The German Low-Grade Lymphoma Study Group reported in 2006 that the median progression-free survival after R-FCM was 16 months without maintenance, and had not reached the median in its maintenance arm.
Currently, the main question to be resolved is whether rituximab maintenance provides a genuine benefit in terms of overall survival. Indolent lymphoma life expectancies are long enough that overall survival studies take considerable amounts of time to complete. However, it is at least possible that the up-front benefit of maintenance is countered by greater resistance to therapy if and when relapse does occur, later on. Long-term studies are needed to confirm the benefits of rituximab maintenance.
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