Stereotactic Body Radiation Therapy for Oligoprogressive Non-Small Cell Lung Cancer

Abstract

<h3>Purpose/Objective(s)</h3> The role of stereotactic body radiation therapy (SBRT) in oligoprogressive non-small cell lung cancer (NSCLC) is controversial, given the current standard of care in this setting favors changing to the next-line of systemic therapy. To address this important knowledge gap, we hypothesized that SBRT in a subset of patients with oligoprogressive NSCLC offers durable response, omitting the need to change or escalate systemic therapy. We evaluated patients on systemic therapy for NSCLC treated at our institution who subsequently received SBRT in the oligoprogressive setting. <h3>Materials/Methods</h3> A retrospective analysis of NSCLC patients who underwent SBRT for oligoprogressive disease from 2017 to 2021 was performed. Variables included in the analysis were age, gender, presence of brain metastases, and number of metastatic sites treated at the time of progression. Lesions defined as progressing were based on the response evaluation criteria in solid tumors (RECIST v1.1); presence of brain metastases was not considered as a site of progression. Progression-free survival (PFS), our primary endpoint, was calculated using the Kaplan-Meier method and defined as the time from completion of SBRT to next progression or death, whichever occurred first. Subset analyses were performed on epidermal growth factor receptor (EGFR) positive patients receiving a tyrosine kinase inhibitor (TKI) and PD-L1 ≥50% vs <50%. Log-rank and Cox proportional hazards regression were used to evaluate predictors of PFS. <h3>Results</h3> A total of 105 patients were included; median age was 65 and 57% were female. The majority were adenocarcinoma (79%). Twenty-six percent of patients were EGFR positive and received a TKI. PD-L1 expression was <50% in 31%, ≥50% in 16% and unknown in 53% of patients. The number of oligoprogressive sites treated at the time of progression was 1-2 in 77% and 3-6 in 23% of patients. At a median follow up of 12 months (range, 1-60 months), median time to progression after completion of SBRT was 4 months (range, 1-37 months). Median PFS for the entire cohort was 5.5 months (95% confidence interval [CI], 2.9-8.0). Median PFS for patients undergoing SBRT to 1-2 vs 3-6 sites of disease was 5.9 months (95% CI, 3.9-7.9) and 3.4 months (95% CI, 1.9-4.8), respectively. Median PFS for EGFR positive patients on TKI was 8.1 months (95% CI, 4.0-12.2), compared to 5.6 months (2.4-8.9) for EGFR negative patients. Median PFS for PD-L1 <50% was 5.6 months (95% CI, 4.0-7.2) vs 6.6 months (95% CI, 0.71-12.5) for PD-L1 ≥50%. Forty-five (43%) patients underwent additional SBRT. No radiation related grade 3 or higher toxicities were reported. <h3>Conclusion</h3> SBRT is a safe and viable treatment option for oligoprogressive NSCLC. Our findings suggest EGFR positive patients and those with 1-2 sites of progression may benefit more. Future prospective studies are needed to validate these findings.