Radiosensitivity of Colon and Rectal Lung Oligometastasis Treated With Stereotactic Ablative Radiotherapy

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Introduction:Patients with metastatic colorectal cancer (CRC) may present with oligometastatic lung lesions for which stereotactic ablative radiotherapy (SABR) can be utilized. This study aims to report efficacy and prognostic factors associated with colorectal lung metastases treated with SABR.Material and Methods:This is a retrospective study including patients who presented with lung oligometastasis from CRC treated with SABR from September 2007 to November 2014.Results:We identified 53 oligometastatic patients with 87 lung lesions. The median prescription dose was 60 Gy in 3 fractions (median biological effective dose of 180 Gy). The median follow up was 33 months. The 1- and 2-year local control, metastasis-free survival, and overall survival were 79.8% and 78.2%, 29.2% and 16.2%, and 83.8% and 69.3%, respectively. On multivariate analysis, rectal primary site (P = .001) and > 2 metastases (P = .02) were significantly associated with a lower local control rate. Rectal lesions were associated with higher radiation dose (169.3 Gy vs. 153.3 Gy; P = .01) and higher rate of KRAS mutations (73.3% vs. 40.4%; P = .02). KRAS mutation did not predict for local control, but predicted for a 1-year metastasis-free survival detriment (0% vs. 37.5%; P = .04), when compared with KRAS wild-type. On multivariate analysis, there is an overall survival detriment associated with gross tumor volume ≥ 3266 mm3 (P = .03) and > 2 metastases (P = .04).Conclusion:In CRC, oligometastatic lung lesions treated with SABR had a worse outcome in patients presenting with a rectal primary, > 2 metastases, or treated with a larger gross tumor volume. More aggressive treatment may be considered in this subset of patients to improve outcome.This study reports outcome of a homogenous cohort of oligometastatic patients treated with stereotactic body radiotherapy for lung lesions arising from colorectal cancer. This study demonstrated lower local control with rectal lesions, which may have a more aggressive biological behavior, as suggested by a differentKRASmutation profile.

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