You're quite clearly correct to note that the tumor response is incredibly important. I'm sure that the reason that some (myself included) are very interested in the CTC count is because of CTC's potential use as a surrogate endpoint for accelerated approval. I know that tumor response is actually much more indicative of clinical benefit (typically defined as extended overall survival horizons or progression-free survival for oncology, for which surrogates are supposed to be an quicker to evaluate proxy), but I think the best chance for AA is through consistent, strong demonstration of an effect on the predominant surrogate endpoint. Thus, the more patients both in and out of the naïve protocol who show drastically reduced - even zero! - CTC counts, the better chance that I believe the company has of seeing not just BTD, but marketing approval.

Obviously, the fact that there is significant tumor response is fantastic news in and of itself, and should be celebrated for more than one reason! But it sounds like significant tumor shrinkage was only noted in NP's mother-in-law. I'm incredibly happy for her, but that also means that the absence of significant tumor shrinkage in patient 1 could highlight the potential importance of patient 2's CTC readings if the goal is simply to get this on the market and start helping people as quickly as possible.

Just my two cents.