Predictors of Radiotherapy Utilization and Outcome in Multiple Myeloma: A Single-Center Retrospective Study
Authors: Naing Phyu Thin , Chukklore Divya , Jung Jessica , Caro Jessica , Evans Clary 
Published: December 2024

Introduction/Background
Radiotherapy (RT) is frequently used in the management of multiple myeloma (MM) for local control and symptom palliation. However, racial disparities and predictors of RT utilization in MM remain underexplored. This study aims to evaluate the relationship between patient demographics, disease characteristics, and RT utilization in a diverse MM patient cohort.
Methods
We conducted a single-center retrospective study of 208 MM patients treated with RT between 2008-2023 at Northwell Health. Patients without a MM diagnosis, initial diagnostic data, or follow up were excluded. We collected data on patient demographics, myeloma risk status based on cytogenetics and Revised International Staging System (R-ISS) criteria, self-identified race, and RT frequency. Statistical analysis was done using Stata v.18. High risk group is categorized as patients who had FGFR3/IGH fusion or t(4;14), MAF/IGH fusion or t(14;16), IGH/MAFB fusion or t (14:20), TP53 (17p) deletion, 1q amplification or stage 2/3 disease. Logistic regression analysis was performed to identify predictors of receiving three or more RT courses, and survival analysis was conducted to assess the impact of repeat RT on patient outcomes.
Results
The study included 124 patients, with race data available for 121 patients. Median age was 66 years, and 51.6% were male. Racial distribution was as follows: African American/Black 35.54%, White 28.93% Asian 6.61%, American Indian or Alaska Native 1.65%, and Others 27.27%. There was no significant relationship between MM risk status and the number of RT courses. However, White patients were more likely to receive multiple RT treatments to the same site of the body compared to all other racial groups (p=0.04). Logistic regression showed age as the only significant predictor for receiving three or more RT courses [odds ratio=0.92, 95% confidence interval (CI) 0.87-0.98, p=0.006], indicating that younger patients were more likely to undergo multiple RT courses. Age at diagnosis negatively correlated with the number of RT courses. At median follow up of 30 months, 36 deaths (29%) occurred. There was no significant difference in overall survival (OS) between patients who received one RT course compared to those who received more than one RT course (p= 0.27). However, survival analysis revealed that patients receiving repeat RT to the same site had higher risk of death compared to those who did not get repeat RT [hazard ratio 2.37, 95% CI 0.70-8.03, p=0.04], with median OS 52.3 months vs. 87.8 months, respectively.
Conclusions
This study highlights significant racial disparities in the utilization of RT among MM patients, with White patients more likely to receive multiple RT treatments to the same site. Age is a significant predictor of RT utilization, with younger patients receiving more courses. Additionally, repeat RT to the same site is associated with shorter OS. However, our study is limited by the sample size and exclusion of patients with insufficient data, with to potential bias. Further studies are needed to explore the role of race in access to RT.