The Natural History of Small Renal Masses

Role of Active Surveillance and Identification of Prognostic Factors for Progression in Early Stage Renal Cell Carcinoma

There is a rising incidence of incidentally detected small renal tumours due to improved imaging techniques. Traditionally, patients diagnosed with these small renal masses undergo surgery and therefore there is limited data about the natural history of these tumours. Several small series have reported that most of these small masses grow slowly and might not require early intervention and that only some masses grow rapidly requiring immediate surgery. Presently, the investigators have not been able to identify prospectively which masses are going to grow slowly. The investigators plan to use computed tomography (CT) and Magnetic Resonance Imaging (MRI) parameters, microsatellite analysis and tissue analysis to determine which masses will behave more aggressively. Additionally, the observations on the natural history of small renal masses need to be validated with a multicentric and systematically followed cohort.

Hypothesis

Since most renal cell carcinomas (RCC's) that are now detected by imaging as small renal masses, grow slowly and remain asymptomatic for years, we hypothesize that:

• Small RCC's that are destined to metastasize do so early or after they reach a larger size
• Delayed surgical treatment of asymptomatic, incidentally detected, small RCC's WILL NOT have a significant impact on overall survival
• The majority of small RCC's MAY NOT need to be treated.
• RCC's that are destined to progress can be identified by abnormal perfusion patterns on imaging and by their cellular and genomic characteristics on needle biopsy.

Inclusion Criteria:

• Asymptomatic T1a (< 4.0 cm) renal mass and unfit for surgery due to advanced age or co-morbidity, OR
• Asymptomatic T1a (< 4.0 cm) and refusal of surgery
• No evidence of metastatic disease (N0M0)
• Preparedness to comply with a close follow-up protocol
• Informed consent

Exclusion Criteria:

• Life expectancy < 2 years
• Already being followed for a small renal mass for more than 12 months
• Concurrent systemic therapy for other malignancies
• Known hereditary renal cancer syndromes