Every oncologist had their own processes, but after a mastectomy seven years ago I had regular checks, three monthly to start, with both my oncologist and surgeon. I still see both once a year, alternating, so I see one of them every six months and have a 3D mammogram with my surgeon at each of his checks, which of course is not required in your case. I didn’t find a lump, so not all that convinced I would know if something was amiss, at an early stage. It may of course depend on your diagnosis but a year certainly doesn’t sound ‘longer than usual’ to me. Can’t see why you can’t ask for a check.