6616 Background: Although cancer remains a leading cause of death, the last few decades have seen improvements in the diagnosis and treatment of the disease. We measure the gains in cancer survival over the last 20 years, and separate these gains into the portions due to improvements in treatment and detection. Methods: We used data from the Surveillance, Epidemiology, and End Results database to calculate cancer survival over time. Our analysis focused on improvements in survival for non-Hodgkin's Lymphoma (NHL), breast cancer, colon cancer, pancreatic cancer, lung cancer, and all cancers combined. Due to data limitations, we calculated survival gains between 1990 and 2000 for NHL, lung cancer, and all cancers combined, and gains between 1980 and 2000 for the remaining cancers. To separate these gains into the portions due to improvements in treatment and detection, we applied the tumor stage data in SEER, which allows us to calculate survival conditional on stage of diagnosis. Since improvements in detection shift the distribution of patients into earlier stages, any improvements in survival conditional on diagnosis at a particular stage are likely to be due to advances in treatment, rather than detection. This empirical approach allows us to separate survival gains into the portions due to improved treatment and detection. Results: We observed large gains in survival during this time period, and most of the gains appear to have been driven by improvements in treatment. The table below summarizes our results. *1990 to 2000. Conclusions: In the past decades, gains in cancer survival have been largely driven by improvements in treatment, even for some cancers (breast and colon) for which there have been increased efforts to improve detection. In these latter cases, the results are attributable to both progress in detection and the surprisingly rapid improvement in survival at every given stage of diagnosis. Cancer Gain in Life Expectancy 1980–2000 (Years) Gain Due to Improved Treatment (%) All* 2.9–3.0 379–86% Breast 5.9–6.0 90–93% Colon 2.8–3.2 65–75% Lung * 0.4–0.5 81–91% NHL* 3.1–3.6 91–98% NHL (Aggressive) * 2.8–3.3 95–100% NHL (Indolent) * 3.6–4.8 95–100% Pancreatic 0.6 71% Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Expert Testimony Other Remuneration Genentech, Inc. Genentech, Inc. Genentech, Inc.