It is important to consider what sort of things can affect the sample collection rate or the results of the DNA testing. Unfortunately there is not a simple black and white answer to this.
Our bodies are fantastic things and it's difficult to say exactly what the effects of specific drugs of treatment can have on it. We know that different people can have the same treatment and experience differing side effects and also the severity of those effects will vary.
With chemotherapy treatment in particular, what we do know that this has the ability to affect the DNA you have. It can damage some of the parts that we look at in order to provide you with results. In this case, we recommend that you allow 6 months from the date of your last treatment to take your DNA sample.
If you have any further concerns about past, present or future treatment and your results with us your healthcare provider is the best most qualified person to answer these, they will have a far greater knowledge than ours and will therefore be able to give you advice that's correct for you.