Clinical characteristics, outcomes and predictors of progression to multiple myeloma (MM) in 61 patients with solitary plasmacytoma

female gender (HR: 0.86; 95% CI: 0.75-0.97); and skeletal related events (HR: 0.77, 95% CI: 0.57-1.02). Conclusions: Older age, male gender, high comorbidity burden, anemia, and hypercalcemia were risk factors for death in the treated NDMM Medicare population. Additional analyses are warranted to understand the relationship between treatments and death. PO-172 Clinical prevalence of monoclonal gammopathy of undetermined significance (MGUS) in the United States: estimating the burden on health care R.S. Go, K. Swanson, L.R. Sangaralingham, E.B. Habermann, R.A. Kyle, N.D. Shah Division of Hematology; Robert D. and Patricia E. Kern Center for the Science of Health Care Delivery, Mayo Clinic, Rochester, MN; Optum Labs, Cambridge, MA Background: Current information on the prevalence of MGUS is mostly derived from serologic testing of population samples. The serologic prevalence is estimated to be 3,200 and 5,840 per 100,000 persons age >50 years for predominantly white and black populations, respectively (Kyle 2006, Landgren 2007). However, in practice, MGUS is almost always discovered only during the evaluation of symptomatic patients suspected of having lymphoplasmacytic cancers. Therefore, the serologic prevalence may overestimate the clinical prevalence of MGUS (Therneau 2012). Methods:We conducted a retrospective analysis of data from 20052014 using the Optum Labs Data Warehouse, a large database including administrative claims information on over 100 million privately insured and Medicare Advantage enrollees throughout the United States. We calculated the MGUS clinical prevalence and assessed trends over time according to year of diagnosis and demographic subgroups. We used the total number of adult (age >18 years) lives covered as the denominator. Prevalence rates were expressed as the number of existing cases per 100,000 enrollees. Changes in trend over time were evaluated using the CochranArmitage test. Results: In 2014, the overall clinical prevalence of MGUS was 100.0 per 100,000. The clinical prevalence differed significantly within demographic subgroups (P <0.001) including sex (male: 94.3, female: 105.4), age (18-29 years: 1.7; 30-39 years: 7.1; 40-49 years: 31.1; 50-59 years: 98.4; 60-69 years: 241.8; 70-79 years: 500.4; 80+ years: 693.4), as well as race and ethnicity (white: 123.5; black: 164.7; Asian: 49.1; Hispanic: 64.1; unknown/unavailable: 67.6). During the 10 year study period, there was a significant increase in the clinical prevalence over time for all patients (27.3 in 2005) and across all demographic subgroups (P <0.001; shown in part in the Figure). Conclusions: The clinical prevalence of MGUS in the US has significantly increased over the past decade, but remains at least 10 times lower than published serologic prevalence. Future public health studies in MGUS should take into account this difference when estimating the burden of medical care. PO-173 Clinical characteristics, outcomes and predictors of progression to multiple myeloma (MM) in 61 patients with solitary plasmacytoma E.E. Manasanch, C.M. Claussen, W. Dong, J. Shah, H. Lee, S. Thomas, V.K. Reed, B.S. Dabaja, S. Milgrom, C.C. Pinnix, S. Parmar, N. Shah, K. Patel, Q. Bashir, M. Qazilbash, R. Orlowski, L. Feng, D. Weber Dept of Lymphoma/Myeloma, The University of Texas MD Anderson Cancer Center, Houston, Texas; Dept of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, Texas; Dept of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas; Dept of Stem Cell Transplantation, The University of Texas MD Anderson Cancer Center, Houston, Texas Solitary plasmacytoma (SP) is a malignancy in bone (BP) or extramedullary soft tissue (EP) at risk for progression to MM. We present preliminary characteristics, outcomes and predictors of progression to MM in a cohort of 61 patients (pt). We retrospectively searched our database for “plasmacytoma” from 1999 until 2014. 192 patients were identified. 131 patients were excluded due to incorrect diagnosis, lack of baseline data or pt duplication. Panel 1A shows baseline characteristics; median follow-up time was 5 years for censored observations. Definitive radiation was a component of therapy in 95% of patients. Median overall survival (OS) was 12.5 years for BP and not reached for EP (p1⁄40.89). Univariate cox hazard model showed larger tumor size and serum paraprotein (SePa) of 1g/dL at diagnosis was associated with worse OS (HR 1.16, p1⁄40.08 and HR 0.24 [for SePa < 1g/dL], p1⁄40.09, respectively). At 5 years, only 17% of EP pts vs. 39% of BP pts had progressed to myeloma (TTM) (p1⁄40.10) (Panel 1B). Univariate analysis of baseline characteristics for TTM identified higher serum calcium (HR 1.30) and location (head and neck versus long bones, 15th International Myeloma Workshop, September 23-26, 2015 e181