Stereotactic radiotherapy is a technique that allows the delivery of a high dose of radiation over few fractions (3-6) with great precision. It thus allows "tumor ablation" and optimal preservation of healthy tissues. Initially developed in small-sized (<5 cm) lung cancers this technique it gives results very close and or even equivalent to those of surgery.

Stereotactic radiotherapy of brain metastases of renal cancers has shown that high doses of radiation allows local control in 90 to 98% of cases. A study conducted in Sweden (Wersall et al.) underline the interest to develop stereotactic radiotherapy in primary renal tumors. In Cleveland (USA) two phase I studies are already underway.

The investigators propose to develop a phase I study for tumors of less than 4 cm. As found in lung cancers, stereotactic radiotherapy can provide a non-invasive, painless and rapid (4 to 5 fractions) method for the treatment of renal cancers with a high rate of local control.

The primary objective is to define the maximal tolerated dose for one fraction in stereotactic mode of renal tumors ≤ 4 cm in length using an a four-step dose increase:

• Step 1: 4 x 8 Gy.
• Step 2: 5 x 8 Gy.
• Step 3: 4 x 10 Gy.
• Step 4: 4 x 12 Gy.

The patients will be followed during treatment with evaluation of acute toxicities before each session, then at 15 days, 6 weeks, 3 months, 9 months, 12 months, and then every 6 months for a total duration of 5 years after treatment.

Inclusion Criteria:

• Patient aged over 75 years with an operable renal tumor or patient with inoperable renal tumor irrespective of age, or patient with metastatic renal tumor and indication for nephrectomy.
• Histologically-confirmed Renal carcinoma less than or equal to 4 cm
• Tumor that is visible and measureable on abdominal scanner and/or MRI (Magnetic Resonance Imaging)
• Karnofsky performance status ≥ 60%

Exclusion Criteria:

• Patient with only one kidney and renal cancer
• Patient not able to cooperate during treatment
• Previous history of abdominal radiation therapy
• Tumor having infiltrated the renal pelvis
• Polycystic kidney disease
• Previous history of intestinal inflammatory disease such as ulcerative colitis or Crohn's disease
• Renal insufficiency (creatinine clearance <30 ml/mm evaluated by DTPA (diethylenetriamine pentaacetic acid ) scintigraphy)
• Uncontrolled hypertension (SBP(systolic blood pressure) above 160 mmHg DBP(diastolic blood pressure) above 100 mmHg with antihypertensive treatment)
• Non primary lesions (benign lesions such as angiomyolipoma, renal metastases,…)
• Antineoplastic and/or antiangiogenic treatment in the month preceding radiotherapy
• Progressive cancer other than renal cancer at time of inclusion with the exception of in situ cervical carcinomas, basal cell carcinoma of the skin, and non-metastatic prostate cancer controlled without hormone therapy
• Participation in another ongoing study that may interfere with the present study