Abstract 1198: Rare isn't rare: Rare cancers compose over 50% of all U.S. diagnoses

Abstract Rare cancers are an understudied and deadly public health problem. Estimates for the percentage of cancer diagnoses that are rare vary depending upon the source cited and the definition of what constitutes a rare cancer. A frequently cited report states that 25% of all adult cancers are rare. However, given the ever-changing landscape of cancer biology and as a result of changes in disease classification, oft-cited percentages underestimate the burden of rare cancers. To address this discrepancy, we reviewed the most recent publicly available data regarding the incidence of all cancers in the United States. Following the NCI definition of a rare disease as one affecting fewer than 15 persons per 100,000 per year, for 2017, a cancer affecting 48,952 or fewer is classified as rare. We considered each cancer individually, acknowledging subtypes based upon the criteria of scientifically accepted definitions, treatments, and histology. We then compiled statistics for each type and subtype. By this method, the total number of estimated new cancer patients in 2017 was 1,685,346, which differed only 0.2% from the Cancer.gov's publicly available estimate of 1,688,780. However, in contrast to previously published data that indicated that 60 of 71 cancer types were rare, we identified a total of 347 cancers, of which 337 were rare. The estimate for rare cancer diagnoses in the U.S. per year was therefore 875,084. Ultimately, 51.9% of all cancer diagnoses are classified as rare cancers by this method. In addition, of 52 major groupings of cancer, 35 (67.3%) disproportionately affect minorities in terms of incidence or overall survival. Seven groupings exclusively or almost exclusively affect women, and 7 additional groups display disproportionate incidence or negative outcomes in women. In addition, while many cancers affect children, and while all cancer in children is rare, at least 55 cancers exclusively or frequently affect children. This analysis clearly shows that the incidence of rare cancer in the United States is widely misunderstood and that cancer in total disproportionately affects historically underserved populations. Treatment options are needed for each form of cancer and should be developed based on a thorough understanding of each disease's biology. In addition, efforts to understand and address the origins of demographic disparities can help reduce disease burden. Citation Format: Katherine Arline, Emily Zeme, Robert L. Treuting, Rodrigo Bravo, Jamie Barber, Christopher Higginson, Jon Goetz, William Siders, Johanne Kaplan. Rare isn't rare: Rare cancers compose over 50% of all U.S. diagnoses [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1198.