RATIONALE: Drugs used in chemotherapy, such as cyclophosphamide, doxorubicin, and vincristine, work in different ways to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. Colony-stimulating factors, such as pegfilgrastim, may increase the number of immune cells found in bone marrow or peripheral blood and may help the immune system recover from the side effects of chemotherapy. Monoclonal antibodies, such as rituximab, can block cancer growth in different ways. Some find cancer cells and kill them or carry cancer-killing substances to them. Others interfere with the ability of cancer cells to grow and spread. It is not yet known whether combination chemotherapy and pegfilgrastim is more effective when given with or without rituximab in treating non-Hodgkin lymphoma.