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2040 Monoclonal Protein Concentration and Risk of Multiple Myeloma: Is 0.5 g/DL the New 1.5?

Program: Oral and Poster Abstracts
Session: 654. MGUS, Amyloidosis and Other Non-Myeloma Plasma Cell Dyscrasias: Clinical and Epidemiological: Poster I
Hematology Disease Topics & Pathways:
Research, epidemiology, Clinical Research, health outcomes research
Saturday, December 9, 2023, 5:30 PM-7:30 PM

Mahta Salehi, MD1,2, Mei Wang1,3*, Kristen M. Sanfilippo, MD1,4, Theodore Thomas, MD1,4*, Martin William Schoen, MD, MPH1,2* and Su-Hsin Chang, PhD1,3*

1St. Louis Veterans Affairs Medical Center Research Service, St. Louis, MO
2Department of Internal Medicine, Saint Louis University School of Medicine, St. Louis, MO
3Division of Public Health Sciences, Department of Surgery, Washington University School of Medicine, St. Louis, MO
4Department of Medicine, Washington University School of Medicine, St. Louis, MO

Introduction: Monoclonal Gammopathy of Undetermined Significance (MGUS) is an asymptomatic clonal plasma cell disorder with a risk of progression to multiple myeloma (MM). To provide an accurate prognosis, monoclonal protein (M-protein) concentration has been used to assess risk of progression to myeloma. Current risk models developed from stored serum samples in a predominately white population of patients indicated a low risk of progression (less than 1% per year) in patients with M-protein of <1.5 g/dL. Little is known about M-protein concentration and risk of progression in patients tested during routine clinical care in a more diverse population. We assessed the outcomes of MGUS five years after diagnosis, and determined the association between baseline characteristics and the rate of progression to MM.

Methods: We used data from national Veterans Health Administration system to identify patients diagnosed with MGUS from 1999-2021 and were followed from MGUS diagnosis until progression, death, or the date 7/11/2023 was reached. MGUS diagnosis and progression to MM was confirmed utilizing a natural language processing algorithm. We included patients of black and white race and those with IgG, IgA, or light chain MGUS. The exposure was M-protein concentration at MGUS diagnosis, stratified by ≤0.5, >0.5-≤1.0, >1.0-≤1.5, >1.5 g/dL. We plotted the cumulative incidence function curve and used a multivariable Fine-Gray sub distribution hazard model with progression at 5 years as the event of interest, and death as a competing event. Covariates included sex, race, MGUS type, age, body mass index (BMI), diabetes, renal disease, and other comorbidities summarized by Charlson Comorbidity Index at MGUS diagnosis.

Results: We included 15,520 patients with MGUS. The mean age at the diagnosis was 71.1. IgG subtype was more common (83.2%) than IgA (12.7%), and light chain (4.1%). 19.6% and 39.5% of patients had renal disease and diabetes, respectively. Black veterans represented 5600 (36.1%) of the cohort. At 5 years, 26.6% of veterans with an M-protein of >1.5 g/dL were diagnosed with myeloma, compared to 11.7% with 1.1-1.5 g/dL, 6.9% with 0.6-1.0 g/dL, and 3.3% with ≤0.5 g/dL. In multivariable models an M-protein >1.5 was associated with a greater risk of progression compared to ≤0.5 (multivariable-adjusted Hazard Ratio [aHR] 9.76, 95% Confidence Interval [CI] 8.37-11.40). Overall, increasing age was shown to have lower risk of transitioning to MM at 5 years with aHR of 0.983 (95% CI 0.978-0.988).

Conclusion: In this modern cohort, only an M-protein of ≤0.5 g/dL was associated with a less 1% per year risk of developing MM. Conversely, 26.6% of veterans with an M-protein level >1.5 g/dL developed MM at 5 years. Risk of MM in patients clinically evaluated for MGUS may be higher than previously thought and new models of MM progression should be developed.

Disclosures: Sanfilippo: Quinn Johnston: Consultancy.

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