Hi Nidge,
Haven't had chemo as yet but use an electric razor and find some areas of fine hair do not cut as well as a few years ago as at my age my hair is not as thick as it used to be. The thin hairs tend to collapse as they are hit by the foil and cutters. I sometimes have to resort to using the beard trimmer on my Braun, on these hairs, particularly after missing shaving for a day or two. This I find shortens these hairs making them less inclined to bend when followed up with the normal cutters to finish the shave. The problem is less if I make time to shave each day. It might be worth trying.