Outcomes of synchronous and metachronous bilateral small renal masses (< 4 cm): a population-based cohort study.

OBJECTIVES: To report longitudinal outcomes of a population-based cohort of patients diagnosed with bilateral small renal masses from a period of over 11 years.

PATIENTS AND METHODS: Consecutive patients diagnosed with bilateral small renal masses (synchronous or metachronous) of a defined geographical area were recorded in a large database (TUCAN database) between January 2005 and December 2016. Patients had a unique identifier number and followed during this period using an agreed upon protocol. Clinicopathological characteristics and outcomes of bilateral small renal masses on active surveillance were analysed and compared to propensity score-matched sporadic unilateral small renal masses. Data were analysed for renal mass growth rate, rate of intervention and development of metastatic disease and patient survival.

RESULTS: A total of 1060 patients were diagnosed with renal cancer, of which bilateral small renal masses accounted for 70 (6.6%) cases. Synchronous SRMs were observed in 63 patients, whereas metachronous lesions were found in seven patients during the study period. Metachronous lesion mean time to appearance was 62 ± 41 months (range 9-149 months). While most cases were sporadic, four were found to be hereditary. Growth rate of bilateral small renal masses did not differ from that of unilateral sporadic small renal masses. Similarly, there were no differences between the groups for rate of interventions and survival.

CONCLUSIONS: Progression, rate of metastases and survival for patients diagnosed with bilateral small renal masses are similar to those diagnosed with unilateral disease.