Lung stereotactic radiotherapy for oligometastases: comparison of oligo-recurrence and sync-oligometastases

Background: Oligometastases can be divided into sync-oligometastases and oligo-recurrence. The difference is whether the primary site is uncontrolled or controlled. The goal of this multicenter study was to evaluate treatment outcomes and factors affecting survival after stereotactic body radiotherapy for pulmonary oligometastases. Methods: The information after stereotactic body radiotherapy from January 2004 to April 2014 was retrospectively collected. Ninety-six patients (65 males, 31 females) were enrolled. Ten cases (10%) were sync-oligometastases, 79 cases (82%) were oligo-recurrences and 7 (7%) were unclassified oligometastases with <6 months of disease-free interval. The median disease-free interval between initial therapy and stereotactic body radiotherapy was 24 months. The median calculated biological effective dose was 105.6 Gy. Results: The median follow-up period was 32 months for survivors. The 3-year overall survival and relapse-free survival rates were 53% and 32%, respectively. No Grade 5 toxicity occurred. The median overall survival was 23.9 months for sync-oligometastases and 66.6 months for oligo-recurrence (P = 0.0029). On multivariate analysis, sync-oligometastases and multiple oligometastatic tumors were significant unfavorable factors for both overall survival and relapse-free survival. Conclusions: In stereotactic body radiotherapy for oligometastatic lung tumors, the state of oligorecurrence has the potential of a significant prognostic factor for survival.