- Patients for whom radiation therapy (RT) to the affected breast or chest wall and regional nodal areas is clinically indicated as per NCCN treatment guidelines, should receive RT after randomization when possible, concomitant with MK-3475 (pembrolizumab) if randomized to the experimental arm; however, RT administered prior to registration is also allowed; patients must specify at the time of screening registration whether or not they will receive RT and the extent of intended RT