Outcomes of Cytoreductive Stereotactic Body Radiotherapy (SBRT) in Patients with Oligometastatic or Oligoprogressive Dominant Lung Metastases from Colorectal Primary

Abstract

Oxaliplatin based systemic therapy regimens have improved the prognosis of patients with colorectal cancer (CRC) and with this, there has been increased interest in the integration of local therapies to oligometastatic and oligoprogressive sites. There is a vast body of literature exploring the benefits of cytoreduction with surgery and stereotactic body radiation therapy (SBRT) approaches. We report our rates of local control (LC) and overall survival (OS) for patients with oligometastatic/progressive CRC with lung metastases treated with SBRT. Single institution retrospective review of patients diagnosed with oligometastatic or oligoprogressive CRC with dominant metastases to the lungs who were treated with SBRT between September 2009 and December 2022. Oligometastatic disease was defined as newly diagnosed, untreated CRC with up to 5 metastases, up to 3 in one organ. Oligoprogressive disease was defined as CRC with 1 - 2 distant sites that continued to progress on active treatment while the primary site was controlled. Survival was estimated using Kaplan-Meier. Association between local control and patient factors was analyzed using log-rank test. A total of 84 patients with oligometastatic or oligoprogressive CRC were treated with SBRT to 124 lung lesions. Colon cancer was the primary site for 54 patients with a median age at time of SBRT of 66 years (IQR 57 - 73) and a median tumor diameter of 1.20 cm (IQR 0.93 - 1.90). Rectal cancer was the primary site for 30 patients, median age was 60 years (IQR 49 - 70) and median tumor diameter was 1.10 cm (IQR 0.80 - 1.48). Median dose for the entire cohort was 6000 cGy (range 5000 - 6000) with median number of fractions 5 (range 3 - 5). Median follow-up after SBRT was 24 months. Overall, there were 9 local failures at last follow-up. Almost half (n = 42) of the patients experienced distant recurrence. Median local control (LC) for the entire cohort was not reached, 2-yr LC and 5-yr LC were 94.6% and 85.7% respectively. There were no differences in LC between colon and rectal cancer (p = 0.29). Actuarial median overall survival was 71 months (95% CI 44.3 - 97.7) and 5-yr OS was 50.2%. Due to the small number of events, we were unable to identify patient factors associated with local failure on univariate or multivariate analysis. Cytoreductive SBRT is an effective treatment option for patients with oligometastatic or oligoprogressive CRC with dominant lung metastases offering excellent rates of LC. Most patients failed distantly highlighting the importance of additional systemic therapies.