Some people are cool and others are anxious. It's cool to go on holiday when a consultant has said take treatment as soon as possible. I'm completely the opposite. Also if he had treatment starting now it might be over by then.
I had a 4 week holiday in Australia booked before I'd any idea I'd got Prostate Cancer. I noticed the date getting nearer and then was told my op could be a couple of weeks before departure so I started planning that I might not go on holiday.
I cancelled bookings that needed a full payment as the payments became due and delayed booking others. That meant I lost the deposit and some of an internal flight.
As luck would have it the surgeon then gave a date 5 weeks earlier, just before Christmas, and I guessed that I might get my post op clinic in just before departure.
The airline, Singapore Airlines, were very good they said ring us the day before departure and you can defer the flight but there will be charge. As another stroke of luck I got a clinic appointment 4 days before departure and was told it was no problem to go. I then re-booked and decided the lost £300 wasn't worth claiming because of insurance excesses. As luck would also have it there was a late booking sale so it made up some of the loss.
Whether you can weave your way round it and still go is worth looking at.