This is a multicenter, single arm phase II study of stereotactic body radiation therapy (SBRT) for patients with medically inoperable primary renal cell carcinoma (RCC).

Primary renal cell carcinoma (RCC) is a common malignancy in Canada. The current standard of care for fit patients with localized RCC is surgical resection of the kidney (nephrectomy). RCC, however, affects predominately an older population with a median age at diagnosis of 65 years. Surgery is often not an option for these patients due to existing co-morbidities, and in an increasing environment of shared decision making in healthcare, some patients decline surgical resection and seek less invasive alternatives.

Stereotactic body radiotherapy (SBRT) is a treatment approach that offers precise delivery of highly conformal radiotherapy to the tumour with minimal exposure to the surrounding normal tissues. SBRT is non-invasive and not limited by the size or location of kidney tumors like other ablative strategies. The worldwide experience of treating RCC with SBRT is growing and the results to date are promising. There is broader enthusiasm from both the radiation oncology and urology community to increase utilization of SBRT for RCC in non-surgical patients within the context of a well-designed prospective trial in Canada.

The investigators will prospectively assess the efficacy, toxicity and impact on quality of life (QoL) of SBRT in the treatment of inoperable RCC

Inclusion Criteria:

• Patients ≥18 years old
• Newly diagnosed RCC by biopsy (preferred) or radiologic evidence of growth on surveillance over two consecutive assessments (6-12 months)
• Primary lesion >3 cm, or recurrent lesion following local ablative therapy
• Medically inoperable or patient who refuses surgery following assessment by experienced urologist, and discussed in a multidisciplinary setting
• ECOG 0-2
• Written informed consent
• Participants must be able to understand the English-language or with the aid of a translator

Exclusion Criteria:

• Primary Lesion >20cm
• Evidence of distant metastatic disease
• Previous abdominal RT in vicinity of kidney preventing definitive SBRT
• History of major radiosensitivity syndrome
• Second invasive malignancy within the past 3 years (excluding non-melanomatous skin cancer)
• Currently pregnant or lactating