Surinder, scanning after 3 cycles is standard for the treatment you’re on. It may well be that it your oncologist will be better able to interpret the scan result because he/she knows what to expect after three cycles. This may well be important in terms of classifying the response as complete/partial/stable/progressive and in terms of disease staging. If the norm is to stage after 3 cycles then doing it sooner might be something your oncologist is unhappy doing.
Personally, I think that if your tumour is responding to treatment then that response will be there after two cycles. I suspect though that your oncologist will resist scanning early…
Pan