This study examines the impact of proton based stereotactic radiation therapy (SBRT) on kidney function as well as other oncologic outcomes including local control, locoregional and systemic failure, progression free and overall survival.

The incidence of kidney cancer diagnosis has been increasing over the last years. Surgical resection represents the mainstay treatment. However, many patients are deemed unfit for surgery due to medical comorbidities or technical limitations. There are non-surgical options including active surveillance, cryotherapy, microwave ablation, radiofrequency and stereotactic radiation therapy (SBRT). SBRT using conventional x-rays has recently been shown to improve outcomes for patients with primary renal cell carcinoma (RCC) in terms of local control and toxicity. However, this treatment was associated with a significant decline in kidney function that necessitates additional intervention including dialysis in some patients. Proton therapy represents an emerging technique with unique properties that allow the bulk of the proton cancer fighting energy to be released at the tumor (Bragg peak) while sparing nearby healthy tissues and organs, particularly the remaining healthy kidney, ipsilateral kidney, bowels, spine and liver. With this technology, both kidneys, the remaining ipsilateral and contralateral, could be spared and thus less damage is expected. This study aims to study the impact of proton based SBRT on the kidney function.

Inclusion Criteria:

1. Age ≥ 18 years
2. Biopsy proven renal cell carcinoma.
3. No clinical or radiographic evidence of metastatic disease.
4. Not a candidate for surgical treatment or local ablative procedures.
5. Subjects are able to undergo either an MRI or administration of contrast agent for CT.

Exclusion Criteria:

1. Prior history of radiation treatment with overlapping fields.
2. Patients with proven metastatic disease.
3. Female subjects who are pregnant or planning to become pregnant during the treatment.