The abstract, published by the ASCO as part of the 2015 annual meeting abstracts released on its website, reveals that Sirtex’s SIRFLOX study of 530 patients revealed median progression-free survival (PFS) in the liver of 20.5 months, an improvement of 7.9 months over the current standard chemotherapy plus Avastin.
SIRFLOX was an international, multicentre, open-label, randomised controlled trial in chemotherapy-naïve patients with non-resectable, liver only or liver dominant (liver plus lung and/or lymph node metastases) metastatic colorectal liver cancer.
Gibbs is a consultant medical oncologist, The Royal Melbourne Hospital, Australia.
The topline preliminary results released earlier this year showed that the study did not meet its primary endpoint, ie, in the first line treatment of non-resectable metastatic colorectal cancer, the addition of SIR-spheres resin microspheres to a current chemotherapy regimen does not result in a statistically significant improvement in overall progression-free survival. However, the study does show a statistically significant improvement in progression-free survival in the liver when SIR-spheres, a liver-directed therapy, are used.
The SIRFLOX study shows an additional 7.9 months (20.5 months vs. 12.6 months), which is a 62.7% improvement in median progression-free survival in the liver for patients whose treatment included SIR-Spheres Y-90 resin microspheres. Patients whose treatment included SIR-Spheres microspheres had a 31% lower risk (HR=0.69) of the tumours in their liver progressing during the time they were on the SIRFLOX study. Study authors confirm that median progression-free survival in the liver was significantly extended and the addition of SIR-Spheres microspheres was associated with acceptable toxicity.
Gilman Wong, CEO of Sirtex said: “The reduction in the risk of tumour progression in the liver, coupled with the statistically significant nature of the result is encouraging.”
Ricky A Sharma, Gray Institute for Radiation Oncology and Biology, University of Oxford, UK, has been independently selected by the ASCO Scientific Program Committee to be the expert discussant for the SIRFLOX study results and two additional abstracts.
A summary of the other key findings in the SIRFLOX study abstract were:
- Overall progression-free survival, the primary endpoint of the SIRFLOX study was not improved in a statistically significant way via the addition of SIR-Spheres microspheres. Median overall progression-free survival was 10.7 months in the SIRSpheres microspheres plus a modified fluorouracil, leucovorin, and oxaliplatin chemotherapy regimen (mFOLFOX6)±bevacizumab arm vs. 10.2 months in the mFOLFOX6±bevacizumab arm, p=0.428.
- Overall tumour response rate, a secondary endpoint in the SIRFLOX study was 76.4% in the SIR-Spheres microspheres+mFOLFOX6±bevacizumab arm vs. 68% in the mFOLFOX6±bevacizumab arm, with a p value of p=0.113.
- Hepatic response rate, a secondary endpoint in the SIRFLOX study was 78.7% in the SIR-Spheres microspheres+mFOLFOX6±bevacizumab arm vs. 68.8% in the mFOLFOX6±bevacizumab arm, p=0.042.
- The complete response rate in the liver was 6% in the SIR-Spheres microspheres+mFOLFOX6±bevacizumab arm vs. 1.9% in the mFOLFOX6± bevacizumab arm, p=0.02. This result indicates that patients who received SIR-Spheres microspheres as part of their treatment experienced approximately a threefold higher rate of complete disappearance of tumours in their liver, compared to patients who did not receive SIR-Spheres microspheres.L
iver resection rate, a secondary endpoint in the SIRFLOX study was 14.2% in the SIR-Spheres microspheres+mFOLFOX6±bevacizumab arm vs. 13.7% in the mFOLFOX6±bevacizumab, p=0.857.
The overall survival data from the SIRFLOX study is required to be combined with the FOXFIRE and FOXFIRE Global studies to provide sufficient statistical power in over 1,000 patients globally to detect a clinical significant difference in overall survival between the SIR-Spheres microspheres and control arms. Overall survival pooled data is anticipated during the first half of 2017.
The study authors concluded “In first-line treatment of patients with non-resectable colorectal cancer liver metastases, the addition of selective internal radiation therapy (SIRT) to standard chemotherapy failed to improve overall progression free survival. However, median liver progression free survival was significantly extended. The addition of SIRT was associated with acceptable toxicity. Overall survival analyses, combining data from SIRFLOX and two other ongoing studies in this disease setting, are awaited.”