Lung Metastases Treated With Stereotactic Ablative Radiation Therapy in Oligometastatic Colorectal Cancer Patients: Outcomes and Prognostic Factors After Long-Term Follow-Up

Abstract

BackgroundWe evaluated a series of oligometastatic colorectal cancer (CRC) patients treated with stereotactic ablative body radiotherapy (SABR) delivered in all active lung metastases. Patients and MethodsForty-four patients with 69 lung metastases were treated with SABR. Eleven patients presented with other sites of metastases before stereotactic body radiotherapy (SBRT), even though they had controlled/cured systemic disease. ResultsThe median follow-up was 36 months. The median overall survival (OS) was 38 months and 2 years, 3-year OS rates were 67.7% and 50.8%, respectively. The median progression-free survival (PFS) was 10 months and 2 years, 3-year PFS rates were 20.3% and 16.2%, respectively. Local recurrence occurred in 16 patients (36%).The first site of failure was local only in 22%, distant only in 35%, and local and distant in 14% of the patients. The 1-year, 2-year, and 3-year local PFS (LPFS) were 68.8%, 60.2%, and 54.2%, respectively. No Grade ≥ 3 toxicities were recorded in the univariate analysis; multiple lung metastases and synchronous oligometastatic disease were significantly associated with worse PFS (P = .04, and P < .001, respectively) and worse metastases-free survival (MFS; P = .04, and P < .001, respectively). The type of response was identified as a significant prognostic factor for OS (P = .014), PFS (P = .006), and LPFS (P < .001). In multivariate analysis single lung metastases treated with SBRT was associated with better MFS (P = .015). Metachronous oligometastatic disease and type of response were associated with significantly better PFS. ConclusionStereotactic body radiotherapy is a valid therapy in the treatment of lung metastases for oligometastatic CRC patients presenting long survival. The rate of local control remains lower compared with other primaries. Further prospective cohorts would better evaluate effective fractionation for patients with oligometastatic CRC.