Utilization of Radiation Therapy in Multiple Myeloma: Trends and Changes in Practice

Background: Radiation therapy (XRT) has been used effectively for the spectrum of plasma cell disorders including plasmacytomas (PLA) and multiple myeloma (MM). Several reports have shown a change in practice for MM therapy including earlier use of combination agent regimens and increased overall utilization of stem cell transplant (SCT) but the role of XRT in the setting of novel therapeutic landscape has not been explored.

Methods: The 2016 National Cancer Database (NCDB) for MM with patients diagnosed between 2004-2013 was studied. Cases without information on the selected patient or facility characteristics evaluated in this analysis, including XRT use, race, median income (2008-2012 dats), insurance status or facility type of initial MM diagnosis and/or treatment were excluded. The association between utilization of XRT as part of initial MM therapy and socio-demographic or treating facility characteristics was studied using multivariate logistic regression analysis.

Results: Of the 123480 unique MM patients in NCDB diagnosed between 2004-2013, 111281 met the inclusion criteria with 7792 patients having osseous PLA (PLA-O; ICD-O 9731), 101919 having MM (ICD-O 9732) and 1570 having extraosseous PLA (PLA-E; ICD-O 9734). Of these, 28232 patients (25.4%) received XRT as a part of their initial therapy. These included 5399 PLA-O (69.3% of all PLA-O), 21891 MM (21.5% of all MM) and 942 PLA-E (60% of all PLA-E). Significant differences were noted for XRT use by most characteristics analyzed. Decreased XRT use was seen with progressively advancing patient age (≥85 year age OR 0.55, 95% CI 0.51, 0.61; ref=<50 year age). Similarly there was a decrease in XRT utilization over time from 2004-2005 (Ref) to 2012-2013 (OR 0.72, 95% CI0.68, 0.77). Men were more likely to receive XRT than women (OR 1.13, 95% CI 1.09, 1.16). There was a significant difference by race where non-Hispanic Blacks were least likely to receive XRT as part of initial therapy for MM (OR 0.89, 95% CI 0.84, 0.93, Ref=non-Hispanic Whites). Socioeconomic factors associated significantly with XRT use included income, where patients with a high income (median income quartile $63000+) were less likely to receive XRT as compared to lower income levels (OR 0.90, 95% CI 0.83, 0.97, Ref=<$38000) and literacy level, where an increasing literacy was associated with a higher likelihood of receiving XRT (OR for <7% no high-school degree 1.10, 95% CI 1.02, 1.19, Ref=≥21% no high-school degree). Insurance payer type influenced XRT utilization as patients with Medicare were less likely (OR 0.86, 95% CI 0.78, 0.94) while those with "Other Government" payer were more likely (OR 1.34, 95% CI 1.12, 1.60) to receive XRT as compared to the reference group of uninsured. There was an interaction with distance from treating facility as patients living between 10-45 miles away were slightly more likely to receive XRT. Patients with a higher Charlson-Deyo Comorbidity Score (Score 2+) were less likely to get XRT (OR 0.72, 95% CI 0.68, 0.77, Ref=Score 0). Treating facility characteristics significantly associated with increased XRT utilization included geographical location in Mountain (OR 1.17, 95% CI 1.01, 1.35) or Pacific (OR 1.18, 95% CI 1.07, 1.30) regions, while characteristics associated with decreased XRT utilization included high-volume facilities (OR for 50+ MM diagnoses seen/year 0.76, 95% CI 0.64, 0.91, Ref=<5 MM diagnoses seen/year) and facilities performing stem cell transplants (SCT) (OR 0.82, 95% CI 0.76, 0.87). There was no statistical difference in XRT utilization between academic and non-academic facilities.

Conclusions: We provide the largest and most comprehensive analysis so far regarding XRT utilization in initial therapy of MM and PLA. We noted an expected higher XRT utilization for PLA as compared to MM and an overall decrease in utilization in recent years, possibly due to advent of highly efficacious systemic agents used as initial MM therapy. Decreased XRT utilization with advancing age may suggest its use as an adjunct to systemic therapy rather than a sole palliative measure since patients with increasing age can now be treated effectively and safely with systemic agents. Centers with higher MM volume and those involved in SCT were less likely to use XRT initially, possibly due to expertise with systemic therapy. Heterogeneity in XRT use based on gender, race and other socioeconomic factors needs to be explored prospectively.