You will also complete the 6-minute walking test. The six-minute walk test measures the distance you are able to walk over a total of six minutes on a hard, flat surface. The goal is to walk as far as possible in six minutes. You will be allowed to self-pace and rest as needed during the walk along a marked walkway. You will complete a 6-minute walk at baseline, at the end of radiotherapy, and 3 months after radiotherapy.