There are one step procedures where you can get a mastectomy with immediate implants depending on your diagnosis. Very few surgeons do this. If you've had a cancer diagnosis and have had or will have radiation it's not recommended that you have implants or expander reconstruction. The best choice there would be tissue transfer (your own tissue, ie: stomach fat, butt fat) such as DIEP flap, IGAP, SIEP or GAP which are all muscle sparing reconstruction surgeries. Then there is also TRAM flap and Lat flap which uses your own muscles which are moved to support the reconstruction.
Best wishes.
When a mastectomy is done there is a considerable amount of skin that is also excised; hence the reason for expanders. This is really a question you should be asking your Plastic Surgeon who has you complete medical history. Regards ....