Predictors and Patterns of Regional Recurrence Following Lung SBRT: A Report From the Elekta Lung Research Group

This study explored the predictors and patterns of regional recurrence (RR) following stereotactic body radiotherapy (SBRT) in 734 cases from a multi-institutional database. The 2-year RR rate was 9%. Stations 4, 7, and 10 were the most common stations for RR following SBRT. These patterns of recurrence may guide nodal staging procedures prior to SBRT. Introduction: The objective of this study was to determine the predictors and patterns of regional recurrence (RR) following stereotactic body radiotherapy (SBRT) for primary lung cancers. Material and Methods: Details of patient factors, treatment, and outcome factors were extracted from a multi-institutional (5) database. All events were calculated from the end of radiotherapy. Estimates of local recurrence, RR, and distant metastases (DM) were calculated using the competing risk method. Cause-specific and overall survival were calculated using the Kaplan-Meier method. Details of locations and number of simultaneous RRs were categorized by lymph node anatomic station. Results: A total of 734 patients were analyzed. The median follow-up was 3.0 years in surviving patients. Four hundred seventy-six (65%) patients had pathologic proof of disease. There were 64 patients with RR. The 2-year local recurrence, RR, and distant metastases rates were 5.6%, 9.0%, and 14.6% respectively. The 2-year cause-specific and overall survival were 89.9% and 63.7%, respectively. There were 136 simultaneous sites of RR. There were 21 recurrences in stations 4R (15.4%), 9 (6.6%) in 4L, 30 (22%) in 7, 19 (13.9%) in 10R, and 14 (10.3%) in 10L. The most common stations for isolated recurrence (n = 19) were station 7 (n = 5; 26.3%) and station 10R (n = 6; 31.6%). The most common RR levels were stations 4 and 7 for right and left upper lobe, stations 5, 7, and 10 for left lower lobe tumors, and stations 7 and 10 for right lower lobe tumors. Conclusion: Stations 4, 7, and 10 were the most common stations for RR. These patterns of recurrence may guide nodal staging procedures prior to SBRT.