Ann: Preliminary SIRFLOX Study Results, page-28

"Sirtex is pleased that the preliminary analysis showed that SIR-Spheres Y-90 resin microspheres did result in a statistically significant improvement in Progression-Free Survival (PFS) in the liver. This secondary study endpoint is important as liver tumours are commonly the only, or dominant, site of disease in patients with mCRC and are the major site of disease influencing survival. Up to 90% of mCRC patients die of liver failure due to the local effects of the liver tumours (1). SIR-Spheres Y-90 resin microspheres are specifically targeted to treat liver tumours."

Not a doctor but this suggests to me that Progression may well be in other sites which have a small effect on overall survival which may be treated by other means. As a patient I would be heartened by this result as it prevents progression in the tumours that are likely to kill me.