K. Ranta1, M. M. Basree2, N. Loconte3, S. Lubner3, M. A. Patel3, N. Uboha3, J. D. Kratz3, D. A. Deming3, N. J. Hurst Jr4, and M. F. Bassetti2; 1University of Wisconsin Hospitals and Clinics, Columbus, OH, 2Department of Human Oncology, University of Wisconsin Hospitals and Clinics, Madison, WI, 3Department of Medical Oncology, University of Wisconsin Carbone Cancer Center, Madison, WI, 4William S. Middleton Memorial Veterans Hospital, Madison, WI
Purpose/Objective(s): The range of appropriate candidates for SBRT to treat metastatic colorectal cancer (CRC) is not well defined with significant variation in national practice patterns. This study extended beyond traditional trial eligibility to include some heavily pretreated patients, and some with a larger burden of metastatic disease for whom there is uncertainty in clinical benefit. Here we report their real-world outcomes. Materials/
Methods: A total of 86 consecutive patients with 261 lesions (median 1) were treated with lung SBRT at a single institution between 2015-2023. 42 patients were treated with 60 Gy in 5 fractions, and 44 were treated 30-60 Gy in 1-8 fractions tailored for patient preference and safety. Toxicity significance was assessed using Mann-Whitney U test, and locoregional recurrence (LRR), systemic therapy free survival (STFS), and overall survival (OS) were assessed using Kaplan-Meier analysis. Results: At the time of SBRT, 60 had prior or current distant metastases outside of the lung, and at least 7 had a history of overt polymetastatic disease. 3 patients had a history of CNS involvement, 4 patients had no primary surgery, and 3 had a history of separate malignancy treated with radiation (head and neck, breast, carcinosarcoma). 10 patients had 6 or more lesions treated. Median follow-up was 23 months. OS was 64% at 3-years, and 50% at 5-years (median 49 mos); freedom from LRR was 33% at 1-year, and 21% at 3-years (median 8.8 mos). 4 patients had grade 2 toxicities potentially related to SBRT, and 1 patient was hospitalized with pneumonitis (grade 3). Toxicity incidence was significantly related to lung V30 but was not significantly related to GTV volume nor number of lesions targeted. Of the 61 patients with greater than 1 year of follow up, 14 were without evidence of disease and more than 1 year from any oncologic treatment at the time of analysis. Of the 18 poorest prognosis patients (CNS involvement, no primary surgery, prior malignancy, 6 or more lesions targeted) OS was 37% at 2 years and STFS was 31% at 1 year. For all 70 patients for which time off systemic therapy was a goal, STFS was 53% at 1 year (median 16 mos).
Conclusion: The use of curative intent oligometastasis directed therapy is well documented and generally recommended for favorable prognosis patients with CRC. Here we observed 5-year OS at the upper end of confidence intervals from published studies which excluded poorer prognosis patients (PulMiCC 38%, CLOCC 43%). In the subset of patients for whom curative intent is not realistic, SBRT was found to contribute to a patient-centric goal with a significant number achieving more than 1 year of systemic therapy free survival.
