Rituxin only therapy

My father has non-hodgkins lymphoma and is having his second round of chemo (first was four years ago). He had his first treatment of bendamustine and rituxin four weeks ago. One week later he was in the hospital with pneumonia. His platelet counts are very low, so they made the decision to take him off the bendamustine and continue with rituxin for the next four weeks. After his platelets go up (if they go up), they will continue with the bendamustine. They think that his platelets might be low because of a spleen problem, and are considering removing his spleen if there is no improvement.

So that's the background. What I want to know is- Has anyone had success with only rituxin? Been on both and then been taken off? They did do a cat scan this week, and his lymph nodes have shrunk, though the tumors in his spleen are around the same size.

Any advice would be great. :)