Abstract 94P
Background
The lung is the most common site of metastases after the liver in rectal cancer patients. The therapy for colorectal cancer patients developing lung metastases is not standardized. SBRT or stereotactic ablative radiotherapy (SABR) has been shown to increase survival rates in oligometastatic disease (OMD). We aimed to investigate how SBRT of lung metastases can delay the progression to polymetastatic disease (PMD).
Methods
We retrospectively analyzed 36 lung oligometastases in 23 patients treated with SBRT from 2014 to 2021 at our institution. The primary endpoint was local control (LC); secondary endpoints were survival and toxicity. Time to PMD was defined as the time from SBRT to the occurrence of >5 new metastases.
Results
The median follow-up was 38 months (9-119). Among 23 patients, 5 were metastatic patients at the time of initial diagnosis. The interval from the first diagnosis to the onset of metastatic disease was 26 months (6-204). The median number of treated metastases was 2 (1-5). In one patient, the lesion was irradiated for the second time due to the progression of the irradiated lesion within 40 months. The median Planning Target Volume (PTV) was 6.7 cc (1.30-17.80) and the median dose was 5000 cGy (1800-5400). Fifty percent of cases received a second SBRT course. The 1-, 2-, and 3-year LC rates were 87%, 64.3%, and 49.6%, respectively. Median progression-free survival (PFS) was 9 months (4-26). Median overall survival (OS) was 38.0 months (95% CI 13.0-28.0), and the survival rates after SBRT were 88.7%, 75.0%, and 57.8% at 1, 2, and 3 years, respectively. The median time to PMD in the overall population was 27 months. Three patients were free from disease and 20 had progression. No grade 3 late side effects were observed. In univariate and multivariate COX analysis, better OS, PFS, and LC were obtained in the histologic grade 1 (G1) group, and tumor size and patients with 1 metastasis, but the difference was not statistically significant.
Conclusions
The present results support local ablative treatment of lung metastases using SBRT in oligometastatic colorectal cancer patients, as it can delay the transition to PMD. A proportion of patients relapse as oligometastatic and can be eventually evaluated for a further SBRT course.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.