Use and impact of selective internal radiation therapy (SIRT) in routine care patients with metastatic colorectal cancer (mCRC).

Abstract

742 Background: The liver is the dominant site of metastasis in patients (pts) with mCRC. Radioembolisation is a potential option in the multidisciplinary management of these patients. Recently initial analysis of a randomised controlled trial (RCT) in the 1st line setting demonstrated no overall progression free survival (PFS) benefit from adding SIRT, but prolongation of liver PFS (HR 0.69, p=0.002) was seen. Methods: Consecutive pts with mCRC enrolled from January 2009 were identified from a prospective multi-site Australian registry. Characteristics and outcomes for pts selected for treatment with SIRT were analysed. Results: Of 1,694 pts with mCRC, 580 (34.2%) had liver only disease at diagnosis, 409/580 (70.5%) with synchronous vs 166/580 (28.6%) with metachronous disease. Of pts with liver only disease, 187 (32.2%) were considered resectable at diagnosis, 100 (17%) as potentially resectable and 293 (51%) were treated with palliative intent. Overall 47 pts received SIRT with 1stline chemotherapy (CT). SIRT treated pts were more likely to have a synchronous presentation (85% vs 68%, p=0.01), liver only disease (83.0% vs 27.3%, p=<0.01), to be ECOG 0 (51.1% vs 34.6%, p=0.01), to be younger (60.8 years vs. 65.9 years, p=0.008) and to be enrolled on a RCT (38.3% vs 7.3%, p=<0.01). In the liver only population treated with palliative intent, SIRT treated pts (n=30) vs CT only pts (n=188) had a median PFS of 10.6 months vs 9.9 months (HR 0.87, p = 0.18) and a median OS of 24.3 months vs 19.3 months (HR 0.73, p = 0.04). Conclusions: SIRT is rarely used in the 1st line treatment of mCRC in routine practice. The available data suggests that OS gains can be seen in the absence of differences in PFS. However, this observed differential effect on survival maybe due to selection biases. SIRT treated patients were significantly younger and fitter than the CT alone group. Future analyses will include a multivariate analysis and examine the impact of the recently presented SIRFLOX trial data on the use of SIRT in clinical practice.