How do you deal with biopsies while patients are on treatment?

In our protocols, we ask that when we get a sample, they have been off treatment for two weeks or more. Going a bit deeper, a sharp person might say that if they have had neoadjuvant pembrolizumab, it has a half life of several months. That is correct, and we do have a fair number of samples that have had prior treatment, including with neoadjuvant immunotherapy. So far, this has not confounded our results. We collect all of that data, so the moment it would start to confound, we would be aware.