In my opinion the results of the trial are definately not conclusive. If anything Kadcyla is equivalent to the chemo + Herceptin arms, and based on adverse events you would still prescribe Kadcyla over the chemo. I believe the trial had a definitive end point and the surrogate measure is progression free survival. So this update actually tells us that Kadcyla at this point is equivalent to the current standard of care. I looked at the FDA web site and found this trial, An Extension Study of Trastuzuma Emtansine in Patients Previously Treated With Trastuzuma Emtansine. It was started this past summer. So that tells me that patients getting Kadcyla in other trials and continue to do well are likely being passed into this trial to measure true survival.
The press release from Roche and the timing seemed to be crafted to maximize the carnage on IMGN, and I wouldn't put it past Roche to do something like that. I won't be surprised if Roche buys them out now. If they don't I think IMGN is in a rocky situation as this news definately delays the royalty stream from Kadcyla increasing.