As I noted on the other board - of 11 Big Pharma onc trials I hunted down, with absolutely no ambiguity in the protocol, 5 had interims, and 2 of those 5 used an interim that, had they stopped at the interim, would have been far from spectacular.
I think the recent ridaforolimus briefing docs indicated that technically they could have stopped at the 2nd interim but the DSMB elected not to. Paradoxically, the advantage of rida over the other arm at that point was 7 weeks - likely enough for approval.