Stereotactic body radiation therapy for lung metastases from colorectal cancer: outcomes and prognostic factors in a series of 109 patients.

Background: Stereotactic body radiotherapy (SBRT) has been applied in the treatment of inoperable lung metastases. We retrospectively evaluated local control (LC) and prognostic factors in patients treated with SBRT for colorectal cancer (CRC) pulmonary metastases. Materials and methods: Unicentric retrospective study of 109 patients with CRC lung metastases treated with SBRT between 2013 and 2020. The prescribed dose was 30-34 Gy in a single fraction or 40-50 Gy in 4-5 fractions. Primary end-point was LC. Secondary end-points included overall survival (OS), progression-free survival (PFS) and identification of prognostic factors that could influence survival and LC. Results: Sixty-eight patients presented rectal cancer and 41 colon cancer as primary cancer. Local PFS (LPFS) at 2 years was 81.0%. The median OS was 51 months with a 2-year OS rate of 85.8%. For PFS, 2-year rate was 30.8% and the median PFS was 11.7 months. No patient experienced grade toxicity ≥ 3. Lesion diameter was the only variable marginally significant for LPFS. Metastases located centrally were associated with a worse OS. The volume (≥ 10 cc), the administration of systemic treatment before or after SBRT and the age (≥ 70 years) were predictive factors for PFS. The volume (≥ 10 cc) and the age (≥ 70 years) were predictive factors for regional progression. Extrapulmonary disease was the most important prognostic factor for distance progression. Conclusions: SBRT proved to be a feasible, safe and effective option for the treatment of patients with CRC lung metastases, with a good LC. None of the prognostic factors studied showed a statistically significant impact on LC.