Natural History and Active Surveillance
The last three decades have seen an increase in the detection of all stages of renal cancers due to widespread imaging. However, the largest increase is seen in cancers less than 4 cm. Surgery, either radical or partial nephrectomy, has been the mainstay of treatment of a small renal mass (SRM) defined as a usually incidentally discovered renal mass <4 cm in diameter which enhances on contrast imaging. There is morbidity associated with this standard of care. However, there has been a change in the management paradigm as a result of observations made on the natural history of SRMs. It is now known that 20 30 are not cancer and histologically benign. This has been demonstrated with surgical series and with data from renal tumour biopsies which have been increasingly performed in the last decade. Even in SRMs proven to be renal cell carcinomas (SRMRCC) the vast majority are low grade and grow slowly. Metastatic progression also appears to be a rare and late event. Initial active surveillance (AS) has therefore emerged as an attractive management option in patients with small renal cancers, especially in elderly patients or those unfit for surgery. Our chapter presents the natural history of the SRMRCC, the current data with renal tumour biopsy and the experience with active surveillance including criteria, suggested protocols and triggers for treatment, and future directions in the changing landscape of renal cancer.