Inclusion Criteria:

• * Less than 30 years of age
• * Diagnosis
• a. Any patient with Wilms tumor or clear cell sarcoma of the kidney who would require radiation therapy as standard of care including
• 1. Any patient with favorable histology (FH), stage III disease
• 2. Any patient with focal or diffuse anaplasia
• 3. Any patient with CCSK
• * The patient is a candidate for external beam radiotherapy based on standard of care for treatment of Wilms tumor or CCSK

Exclusion Criteria:

• * Prior radiotherapy to the region of the study cancer
• * Chemotherapy administered for diagnosis of Wilms tumor or CCSK
• * Pregnant or breastfeeding