Trends in the Utilization of Radiation Therapy (XRT) Among Patients with Non-Hodgkin's Lymphoma (NHL) in the United States (US)

Background: The treatment of NHL has witnessed a paradigm shift over time, with targeted immunotherapy, stem cell transplant (SCT) among others. Historically, XRT was used quite frequently for the management of NHL but with advent of better systemic therapy, its utilization has changed. Trends and patterns of care for XRT use have never been formally reported.

Methods: We identified patients with NHL diagnosis in the National Cancer Database (NCDB) between years 2004 and 2015. Demographic, clinical, facility level, initial treatment and outcome data were collected. The utilization of XRT in diffuse large B-cell (DLBCL) and non-DLBCL NHL were analyzed separately by univariate and multivariate analyses. To analyze the trends in the rates of XRT, we applied segmented linear regression to calculate the average annual percent change (AAPC) and 95% confidence Interval (CI) with a 'p' value. AAPC and CIs were calculated using the segmented package in R studio v1.1.49. Rest of the analyses was conducted using StataCorp version 15.1.

Results: A total of 133,182 DLBCL and 204,933 non-DLBCL patients were identified. Among patients with DLBCL, 27,895 (20.9%) patients received RT. The rate of XRT declined from 25% in 2004 to 18.4% in 2015 with estimated AAPC of -0.59% (95%CI: -0.70- -0.49), p= 0.03 (Figure 1). In a subgroup analysis, a similar decline in the rate of XRT was evident across all the age groups, combined stages I and II vs stages III and IV and nodal vs extra nodal DLBCL (Table 1). Among non DLBCL, 33,369 (16.3%) patients received XRT. There was a statistically significant decline in the rate of XRT from 18.03% in 2004 to 16.3% in 2014 with an AAPC of -0.26 (95%CI: -0.38- -0.14) p <0.001 (Figure 1). On the subgroup analysis, the utilization of XRT declined across all the studied subgroups except among patients aged 80 years and above (Table 1). On multivariate analysis, several demographic, clinical and facility level factors were found to be significantly associated with XRT utilization in NHL (Table 2). In particular, older age groups, racial/ethnic minorities, advanced stages, higher Charlson comorbidity scores and diagnosis in the more recent calendar years were associated with lesser chances of receiving RT. Extranodal DLBCL had lower utilization while extranodal non-DLBCL had increased XRT utilization.

Conclusion: There has been a significant decline in the utilization of XRT among patients with NHL (DLBCL and non-DLBCL) in the US since 2004, likely due to introduction of practice changing systemic therapeutics. There is still significant heterogeneity noted in practice patterns regarding utilization of XRT across the US. Having more standardized guidelines will help streamline delivery of evidence-based patient care.

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