A Study of Rituximab Combined With Prednisone for the Initial Treatment of Chronic Graft Versus Host Disease (cGVHD)

Inclusion Criteria: * Previously untreated symptomatic classical C-GVHD (with prior allogeneic stem cell transplant) requiring systemic therapy (defined as per NIH Consensus: a)At least 3 sites of organ involvement or individual organ score of at least 2, b)Patients on agents for GVHD prophylaxis (such as therapeutic dose or tapering cyclosporine A or tacrolimus) or patients that have received therapy for acute GVHD prior to enrollment are eligible * Patients must be 18 years of age or older * Eastern Cooperative Oncology Group (ECOG) performance status of 0-2 * Patients must be accessible for treatment and follow-up. Patients registered on this trial must be treated and followed at the participating centre. Investigators must assure themselves the patients registered on this trial will be available for complete documentation of the treatment, adverse events response assessment and follow-up. * Patient must be willing and able to complete the GVHD questionnaire * For patients that have been started on prednisone therapy for cGVHD but otherwise meet all of the eligibility criteria, registration into this trial must occur no later than 14 days from the start of prednisone therapy. Exclusion Criteria * Uncontrolled infection at the time of study enrollment * Recurrent malignancy at the time of study enrollment * Previous systemic therapy for C-GVHD, a)Patients on agents for GVHD prophylaxis (such as therapeutic dose or tapering cyclosporine A or tacrolimus) or patients that have received therapy for acute GVHD prior to enrollment are eligible. b)Patients who have been restarted on full doses of agents used for GVHD prophylaxis (ie. cyclosporine A or tacrolimus) after these have tapered or discontinued are not eligible * Inability to tolerate prednisone (includes pre-existing myopathy, diabetes with poor glycemic control, uncontrolled hypertension or fluid retention) or rituximab * Usage of additional concurrent agents which could treat C-GVHD (ie. chemotherapeutic agents - cyclophosphamide, methotrexate or other immunosuppressive agents). Patients may be continued on stable or tapering dose of GVHD prophylaxis agents such as cyclosporine or tacrolimus, but must be tapered off by first study treatment * The administration of anticancer therapies or other investigational agents is not permitted. Use of hematopoietic colony stimulating factors to manage blood counts is allowed. * Sexually active males and females of childbearing potential unwilling to practice contraception during the study. Patients of childbearing potential must be willing to use a reliable method of birth control (i.e. double barrier method). * Women of childbearing potential with either a positive or no pregnancy test at baseline or lactating. Postmenopausal women must have been amenorrheic for at least 12 months or surgically sterile to be considered of non-childbearing potential. * Patients with immune deficiency are at increased risk of lethal infections. Therefore, HIV-positive patients receiving combination anti-retroviral therapy are excluded from the study because of possible pharmacokinetic interactions. * Patients with active hepatitis B are excluded