Clinical guidelines recommend patients with Diffuse Large B-Cell Lymphoma (DLBCL) receive anthracycline-based chemotherapy (ABC) treatment. During the 1990s, however, about one- third of elderly DLBCL patients did not receive chemotherapy, potentially due to intolerance of toxicities associated with ABC.  With the addition of rituxmab in the late 1990s, it appears that physicians choose to use non-guideline rituximab plus non-ABC chemotherapy for patients with low toxicity tolerance. OBJECTIVES: This study assesses the diffusion of the use of non-guideline chemotherapy treatment for elderly DLBCL patients and examines the regional variation in diffusion. METHODS: A retrospective cohort consisting of 5839 Medicare beneficiaries diagnosed in 2000-2006 with primary DLBCL at age 66 or older treated with any chemotherapy was selected from the 2007 Surveillance, Epidemiology and End Results (SEER)-Medicare linked database. Patients were excluded if physician information was not available (N=55). Patient chemotherapy was categorized using Medicare claims within five months of diagnosis. Physicians (N=3,072) were included if they prescribed any chemotherapy to patients during the initial treatment period. Descriptive analyses were used to characterize variation in chemotherapy treatment across the SEER registry regions.   RESULTS: Physicians prescribed ABC chemotherapy to on average 81.2% of received chemotherapy patients. A totla of 19.8% of physicians, however, prescribed rituximab plus non-ABC chemotherapy to at least one patient. The percentage of physicians whom used rituximab plus non-ABC chemotherapy increased from 1.4% in 2000 to 16.1% in 2006. Louisiana, Connecticut, and Seattle were the top three SEER regions where over 23% of the physicians prescribed this alternative chemotherapy. In Hawaii, New Mexico, and Iowa SEER regions less that 14% of physician used this alternative chemotherapy. CONCLUSIONS: The percentage of physicians having adopted rituximab plus non-ABC chemotherapy as the alternative treatment increased over the years. Physicians’ adoption of non-guideline treatment varies across regions.