Facility-Level Analysis of Twice Daily Radiation Utilization for Limited Stage Small Cell Lung Cancer

Abstract

Treatment of limited stage SCLC (LS-SCLC) with twice daily (BID) fractionation (fx) to 45 Gy remains the standard of care for many decades. However, many patients receive once daily (QD) treatment as outcomes appear similar. Recent data have suggested that dose escalation to 60 Gy BID may improve outcomes, stressing the importance of BID delivery for SCLC. In this study, we examined the use of BID fractionation across treatment facilities and hypothesized that a substantial number of centers may never utilize BID treatment. The National Cancer Database (NCDB) was used to identify U.S. facilities treating LS-SCLC patients with definitive chemoradiation from 2004 to 2019. Included patients had stage I-III disease, received doublet chemotherapy, and did not undergo surgery. All patients received thoracic radiation therapy (RT), defined as QD (59.4-70.2 Gy in 30-39 fx) or BID (45 Gy in 30 fx). Other RT regimens were excluded. Facilities were classified into two cohorts (BID-treating and QD-only) based on whether or not at least one patient received BID treatment over the study period. Facility-level statistics including facility type, geographic location, and facility volume were analyzed. Predictors of BID-treating facility classification were determined using Chi-squared tests and uni/multivariable logistic regression. From 2004 to 2019, 22,545 LS-SCLC patients were treated by 1,222 facilities. Of the 1,222 facilities, 832 (68%) were BID-treating facilities while 391 (32%) were QD-only facilities. On univariable analysis, facility type (community cancer program, comprehensive community cancer program, integrated network cancer program, or academic program; p = 0.783) and geographic location (Northeast, Midwest, South, West; p = 0.417) were not associated with classification as a BID-treating facility. In contrast, facility volume was significantly associated with classification as a BID-treating facility, with BID use noted in 42.8% of the lowest quartile volume facilities vs. 84.0% of the highest quartile volume facilities (p<0.001). Dichotomized facility type (academic vs. non-academic), geographic location (South vs. other), and facility volume (greater or less than median volume) were included in a multivariable analysis. Facility volume (p<0.001) remained significant while facility type (p = 0.956) and facility location (p = 0.516) remained insignificant. Despite evidence supporting BID fractionation as the standard of care for LS-SCLC, 32% of facilities have never delivered BID treatment over the 15-year study period. Facilities with a low volume of patients are most likely to use QD-only. Barriers to BID treatment adoption will need to be overcome if dose escalated BID fractionation defines a new standard of care for LS-SCLC.