Abstract 492P
Background
Stereotactic ablative radiotherapy (SABR) has been shown to increase survival rates in oligometastatic disease (OMD) in colorectal cancer, but local control of colorectal metastases still remains poor. We aimed to identify potential predictive factors of SBRT response through a multicentre large retrospective database and to investigate how lung SBRT can delay the progression to polymetastatic disease (PMD).
Methods
The study involved 17 Italian centers, and was approved by the Ethical Committee (Prot. Negrar 2019-ZT). The early results from the first 463 lung metastases treated with SBRT in 276 patients are hereafter reported. EGFR, KRAS, NRAS and BRAF were evaluated as potential predictive biomarkers for SBRT response. Lesion diameter GTV, PTV volume, site of primary tumour were also evaluated. Secondary endpoint was the time to polymetastatic conversion (ttPMC).
Results
The median follow-up was 26 months (range 3-80 months). The median lesion diameter was 13 mm (range 5-58 mm). The 2- and 3-year local progression-free survival (LPFS) were 71.8% and 70.2%, respectively. At the univariate (UV) analysis, KRAS was significantly correlated with better LPFS (3-year LPFS: 85% versus 56% for mutated and wild-type KRAS; P=0.002). Moreover, at the ROC curve analysis, a lesion diameter threshold <20 mm significantly correlated with LPFS (P=0.00). The median ttPMC was 17 months (range 14-22 months) and the 1- and 2-year ttPMC was 59.5% and 40.4%, respectively. At the median follow-up, 66 patients were free from disease and the others progressed as sequential oligometastatic disease (SOMD) (189), and polymetastatic (21).
Conclusions
The present interim results support the use of local ablative treatment of lung metastases using SBRT in oligometastatic colorectal cancer patients as it might delay the transition to PMD. Mutated KRAS seems to be associated with improved control of treated metastases and can be considered as a potential predictive factor.
Clinical trial identification
Prot. Negrar 2019-ZT.
Editorial acknowledgement
N/A
Legal entity responsible for the study
Prof. Filippo Alongi.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.