Clinical Trial Objectives

As someone with no medical expertise could someone with expert knowledge tell me whether the primary objective of the Sirflox trial had to be an improvement in overall progression free survival or whether the achievement of improved PFS in the liver could have been the aim? Given that the SIR Spheres only address tumours in the liver would it not have been more appropriate that the primary objective related to improvement in that area alone? Such improvement was indeed demonstrated. Had the primary endpoint been described as PFS in the liver, with a secondary target the achievement of overall PFS, which seems more logical since the treatment addresses the liver alone, the result of the trial would have been very differently received.