Benefit of post-operative radiation therapy for incompletely resected stage I-IIIA non-small cell lung cancer: An analysis of the National Cancer Database.

8558 Background: The presence of micro-residual (R1) or macro-residual (R2) disease in non-small cell lung cancer (NSCLC) is associated with a higher risk of recurrence. The benefits of post-operative radiation therapy (PORT) in incompletely resected NSCLC is not clear. The purpose of this study is to compare median overall survival (mOS) of treatment modalities in the post-operative setting for resected stage I-IIIA NSCLC with residual disease (R1/R2) and to determine if PORT provides benefit in this patient population using the National Cancer Database (NCDB). Methods: From the NCDB dataset for the years of 2006-2016, we extracted patients diagnosed with stage I-IIIA NSCLC and who had incomplete resection with residual disease (R1/R2). Kaplan-Meier analysis was performed to differentiate the effect of different post-operative treatment modalities, concurrent chemo-radiotherapy (CCRT), sequential chemo-radiotherapy (SCRT) and chemotherapy (CT) alone on mOS. Subsequently, univariate Cox regression was used to identify statistically significant variables, then multivariate Cox regression was performed to establish variables that contributed to the survival. Lastly, multinomial logistic regression was utilized to establish association of the independent factors. SAS version 9.4 was used to analyze the data. Results: Among the 2701 patients who met inclusion criteria, the average age was 64.1, 64.8 and 65.9 year old for CCRT, SCRT and CT, respectively. Male's constituted 53.6% and white's were 88.1%, and patient's were distributed equally across clinical stages. The majority of patients received SCRT (51.7%) followed by CT alone (39%), and CCRT (9.2%). There were no statistically significant differences in mOS between the different treatment modalities (p=0.220). Patients with R2 were 177% more likely to receive CCRT than CT compared to R1 (OR 2.77, CI 1.86-4.13 and p<0.001). Male's were 28% more likely to receive SCRT than CT compared to females (OR 1.28, CI 1.08-1.52 and p=0.0041). Nodal involvement was associated with decreased mOS with N2/N3 having 37% lower mOS compared to N0 (HR=1.37, CI 1.19-1.57 and p<0.0001). Patients who had R2 disease had a 38% lower mOS compared to those R1 (HR 1.38%, CI 1.19-1.62, p<0.0001). Conclusions: Despite the risk of unfavorable outcomes for patients with residual disease after surgery for NSCLC, the addition of radiotherapy, either concurrently or sequentially, to CT did not offer statistically significant mOS benefit compared to CT alone. Given the known toxicities of radiation, and the lack of impact on survival, the benefit of post-operative radiation is questionable among patients with residual disease after resection.