What Bras are best during Radiotherapy?

Hi lovely ladies

I live in rural Queensland and am about to commence 6 weeks or so radiotherapy in Brisbane. 

I have a large bust (14DD) and while that was an advantage for the lumpectomy, I am wondering what bras to wear during the 6 weeks treatment?  I do not look great without a bra but concerned that they could rub the skin and cause a problem.   I also read about wearing a t shirt under the bra.

Can you advise me what you did during treatment? 

Being away from home for 6 weeks means that I need to carefully consider what I pack for this trip.  

Appreciate any advice.

Thanks Glennie xx