No Difference in Outcomes for Non-Small Cell Lung Cancer Treated With Stereotactic Body Radiotherapy Based on Pathologic Diagnosis

Abstract

According to society guidelines, stereotactic body radiotherapy (SBRT) can be delivered in patients who have a lung lesion that is clinically and radiographically consistent with non-small cell lung cancer (NSCLC) and refuse biopsy, have undergone a nondiagnostic biopsy, or are at prohibitive risk of biopsy. The purpose of this study is to report outcomes of patients with stage I-II NSCLC, with or without pathologic diagnosis, treated with SBRT at our institution.We performed a single-institution retrospective review of patients with early-stage node-negative NSCLC who received curative-intent SBRT between 2005 and 2018. We included patients with biopsy-proven NSCLC or presumed NSCLC based on radiographic findings. We calculated outcomes using the Kaplan-Meier method and used a log-rank test to assess prognostic impact.The study population consisted of 175 patients and 186 individual lung nodules with a median follow-up time of 2.6 (range, 0.1 - 12) years for all patients, and 3.5 (range, 0.2 - 8.4) years for living patients. The median age was 70.2 (range, 43 - 90) years and the median maximum tumor diameter was 1.9 (range, 0.7 - 5.6) cm. Twenty-three (13.1%) patients had a history of previously treated NSCLC, and more than a third (n = 66, 37.7%) of patients were oxygen-dependent at the time of SBRT. One hundred and seven (61.1%) patients were treated empirically with SBRT without a pathologic diagnosis. Most tumors were peripheral with only 9.7% (n = 18) centrally located, and most were located in the upper lobes (n = 123, 70.3%). The median prescription dose was 50 (range, 48 - 62.5) Gy in 5 (range, 4-10) fractions. Among the entire cohort, the 3-year rates (95% confidence interval) of local control, regional control, cause-specific survival, and overall survival were 81.0% (73.8% - 86.5%), 89.5% (82.7% - 93.8%), 72.4% (64.5% - 79.1%), and 48.3% (40.7% - 55.9%), respectively. There was no difference in local-regional control (P = 0.76), cause-specific survival (P = 0.75), or overall survival (P = 0.33) between patients with a pathologic diagnosis and those without. We observed late grade 3 toxicities in 2.3% of patients and no higher-grade toxicities.Patients without a pathologic diagnosis of NSCLC had no difference in disease outcomes compared with patients that had biopsy-proven disease, suggesting that empirically treating patients with a radiographic diagnosis of NSCLC is a reasonable alternative when a biopsy cannot safely be attained.