Margriet Kwint

Outcome of treatment of synchronous oligometastases 53 3 (N=25), adrenal gland: 3x8 up to 3x12.5 Gy (N=11), or bone: 3x8 Gy up to 3x15 Gy or 5x7 Gy (N=9)). Other treatment modalities such as radiofrequency ablation (RFA (N=1)) were considered radical as well. In general, the clinical outcome of the treatment was evaluated 8weeks after treatment by clinical consultation and repeat CT. Subsequently, follow-up was performed every 3 months by the pulmonologist and radiation oncologist or surgeon. After 2 years, follow-up was performed every 6 months. In case of brain metastases, a MRI-brain was performed every 3 months. Primary endpoints were progression free survival (PFS) and overall survival (OS). Survival was calculated from date of pathologically proven diagnosis until the last date of follow-up or death. PFS was calculated from date of pathologically proven NSCLC until the date of first progression (local, regional, distant) or death. Progressive disease was scored based on available clinical data or imaging report of tumor progression. Statistical analysis Descriptive statistics were used for patient, tumor and treatment characteristics. Median OS and PFS were calculated using the Kaplan-Meier method. Median follow- up was calculated using the reverse Kaplan-Meier method. Univariate Cox regression analysis was done on patient, tumor and treatment characteristics to identify predictors of OS and PFS. P-Values were used to quantify degree of association between each of the factors and the survival-based endpoints. Multivariate Cox regression analysis was performed for OS and PFS, based on selected variables from univariate analysis (p < 0.10). Multivariate analysis was done by backward selection, based on p-value with a removal criterion of p=0.10. Statistical analysis was carried out by using SPSS (version 22). Results Patient selection and treatment variables Table 1 presents the baseline patient and tumor characteristics. Between July 2008 and August 2016, 91 patients with a mean age of 60 years (range 35-86) were treated and registered in the database and eligible for this analysis. Seventy-seven (85%) patients had a solitary metastasis, 9 (10%) patients had 2 metastases, 2 (2%) patients had 3 metastases and 3 (3%) patients had 4 metastases. The most frequent location