The trial is open to patients who have metastatic renal cell carcinoma/urothelial (bladder) carcinoma with at least 2 measurable sites of disease. All eligible patients will be randomly assigned to immunotherapy(nivolumab/atezolizumab) versus immunotherapy (nivolumab/atezolizumab) plus radiotherapy, 10 Gy x3 (conformally or by intensity modulation radiation therapy/Image-guided radiation therapy (IMRT/IGRT) to maximally spare normal tissue), to one of their measurable lesions.