Nicholas Trakul MD, PhD, Abstract Co-Author: Nothing to Disclose

Lisa Jacobs, Abstract Co-Author: Nothing to Disclose

Billy W. Loo MD, PhD, Abstract Co-Author: Speaker, Varian Medical Systems, Inc Speaker, General Electric Company

Maximilian Diehn MD, PhD, Presenter: Nothing to Disclose

Stereotactic ablative radiotherapy (SABR) is increasingly being utilized for patients with oligometastatic lung tumors. Data on outcomes for oligometastatic tumors treated with SABR remain relatively limited and we reviewed outcomes of such patients treated at our institution.

We retrospectively reviewed patients with lung metastases treated with SABR at Stanford between July 2003 and July 2011. We identified 50 patients with a total of 74 lesions. The number of lesions treated ranged from 1 to 4. A variety of SABR regimens were used, with the majority receiving 25 Gy in 1 fraction or 50 Gy in 4 fractions. The median biologically effective dose was 87.5 Gy. We analyzed local control (LC), overall survival time (OS), and time to next treatment and stratified patients by clinical factors such as histology, number of lesions, and if patients had received previous treatment. Relevant toxicities were scored.

Median follow up time was 10.5 months (range 3 to 51 months). For the entire cohort, OS and LC at 12 month were 89.1% and 82.1%, respectively. Median OS was 29 months and median LC was not reached. The only factor which was strongly associated with LC was tumor histology. Specifically, colorectal cancer metastases had significantly worse local control than other tumor types. LC at 12 month was 29.5% for the 19 colorectal cancer metastases and 93.6% for all other histologies (p<0.0001). Other factors, such as number of lesions or previous treatment were not significantly associated with LC. Excluding colorectal cancer patients, median time to next systemic treatment was 30 months and median OS was 31 months. Clinically significant toxicity was minimal, with 1.9% of patients experiencing Grade 3 toxicity and no Grade 4+ toxicities.

Our analysis demonstrates that among patients with oligometastatic lung tumors, those with metastases from colorectal primaries demonstrated significantly worse LC. We find that carefully selected patients with oligometastatic disease have encouraging post-SABR systemic treatment-free intervals and OS rates, indicating that prospective studies examining efficacy of SABR for oligometastatic tumors are warranted.

SABR is a promising treatment option for patients with oligometastatic lung tumors and leads to excellent local control and treatment free survival except possibly for colorectal cancer metastases.

Trakul, N, Jacobs, L, Loo, B, Diehn, M, Stereotactic Ablative Radiotherapy for Oligometastatic Lung Tumors.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12034649.html