@Outra, hi and welcome. What a hard decision to have to make.
There are so many treatments that are available, that vary in side effects and long term issues, that you need to take them one step at a time.
The overwhelming nature of a breast cancer diagnosis can stun you into blankness.
Depending on the grade, stage and nature of your cancer, many options are open to you and you get to choose which ones you will go through, though the specialists seem to assume you will go through them all, as I have/am without question.
Having been through mastectomy, I think that is the least difficult of the options to deal with physically, it opens up its own issues of finding clothes, especially if you only have one off, but could be all you need.
In order to make your choice you really need a lot of information and this can be difficult to process to start with.
I used a psychologist at the Cancer Centre near me to process my decision on whether to remove one breast or two ( only one apparently had cancer)
They were very helpful in steering me out of the mess of emotions and getting me to focus on what would ultimately make my decision.
I was going through an angry stage where I was highly likely to cut my nose off to spite my face!
The Psychologist was free.
Unlike the specialists who focus one the one area, the psychologist was helpful in dealing with all areas of treatment and my feelings about them. They also allow one hour and I didn't feel rushed in the appointment, unlike appointments with most of the specialists.
I also could come back several times to work on the problem.
The decision doesn't have to be treatment or no treatment, it can be picking and choosing what treatment will be the most benefit with the least amount of damage to your already compromised body.
I hope you can work out what you really want to do in this shitty situation, with as much information as you can. It really isn't fair, is it?