What I'd say is : if you're more comfortable, less sore, do wear a bra at night. If it doesn't make a difference, or you're actually sleeping better without one, don't wear one!! A bra isn't necessary unless it helps with the pain.
Straight after my lumpectomy, I went bra-less for maybe a couple of nights as the slightest touch would make me howl. Then I used a much larger than my own size post surgery bra, front fastening, very stretchy, hardly any support (it looked more like a crop top), but the little it did was a life savior at the time. I was hot, but it was worth it for the comfort it offered, on my swollen, bruised boob and side. After about 3 weeks, The bra was off again at night.
3 weeks ago I had my biopsy and was diagnosed with IDC and Paget's Disease. The surgeon said wear your bra at night it will help. As I live in Cyprus and it wont be long before the nights are hot and wearing a bra in bed would not be on my wish list unless absolutely necessary. Can anyone offer me advice on this please. I am still very swollen after one chemo session, no reduction yet!