Pencil Beam Scanning in Patients With Renal Tumors

This trial is studying whether a very precise type of proton radiation treatment (called pencil beam scanning — which targets tumors with extreme accuracy to protect surrounding healthy tissue) is safe and effective for children with kidney cancer (Wilms tumor or clear cell sarcoma of the kidney). **You may be eligible if...** - You are under 30 years old - You have been diagnosed with Wilms tumor or clear cell sarcoma of the kidney (CCSK) - Your doctors have recommended radiation therapy as part of your standard care - You have specific cancer staging or features that require radiation (e.g., Stage III, anaplasia, or CCSK diagnosis) **You may NOT be eligible if...** - You have had prior radiation to the same area - You have not yet received chemotherapy for your kidney cancer diagnosis - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.