Background: A few years ago, at the time of joining my PhD, I submitted a proposal which was eventually approved by the institute and the ethics committee. At the time when I proposed this work, there were barely a couple of papers on the topic and it seemed quite novel. Now, I have submitted my thesis and have just received my reviews from two external reviewers. During this time, as expected, many other people have got into the field. Unfortunately for me, I have not been able to publish my thesis results yet, so I have missed out on cashing in on the head start.
Now, one of my reviewer is questioning the novelty of my work. There are still a few novel aspects to my thesis in the sense of how I have approached the problem, although some of the novelty has been lost simply because there are some recent papers that have shown similar, if not the same, results. The important point is that most of these recent papers are in the past 1-1.5 years.
Typically in the kind of PhD program I am enrolled in, one submits a proposal and then works on them till they submit. Modifications are usually not the norm. Part of the reason why I couldn't finish my thesis before these papers started kicking in is wanting to be much more sure about the results (given that I come from a completely different field with zero background), lack of (enough) data at the right time, learning the ropes of the game, and intermediate lack of funding situation (committed funds not arriving at the right time), etc.
Question: In programs like the one I am enrolled in, can one justify novelty based on the fact that when the study was initiated, it was quite novel and that it is only in the past 1-1.5 years that people have started publishing? Another way to look at the question would be: are there any good ways to "post-hoc" justify novelty?
A similar situation (without the PhD context) would be that a reviewer recommends rejection of a novel paper after a similar paper got published (while your paper was under review).
Additional note: my advisor agrees that there are still novel aspects to my thesis and they feel that the reviewer is "asking for too much from a PhD thesis"
Edit: The reviewer has recommended the thesis; this means that I will be writing a response to the comments I have received (including making some corrections/changes as needed) and then there will be a viva/defence