Indirect evidence from the small non-cystic renal mass literature has supported the role of active surveillance as a management option for complex renal cysts.5, 8, 10, 11, 16, 21−24 Two recent retrospective studies have also reported the outcomes of patients with a complex renal cyst who opted to be managed by active surveillance.17, 18 The average cyst sizes in the two studies were 4.1 cm and 3.5 cm for Bosniak III cysts, and 3.1 cm and 3.8 cm for Bosniak IV lesions, respectively. Both studies have suggested that this approach could be safely used in this population, with only one death due to kidney cancer observed after 5 years of follow-up in these studies. Moreover, only two patients with a Bosniak IV cyst developed a metastasis out of 243 patients with a Bosniak III or IV cyst (0.8%) – both of whom had refused surgery despite evidence of local progression. Criteria for lesion progression included increase in cyst size, increase in vascularity, and increase in size of the solid component. Importantly, during the 5-year observation period, 65% of patients avoided surgery given the absence of lesion progression, and among patients who progressed, 16.5% were found to have a benign tumor on final pathology. While these results are encouraging, given the low quality of existing evidence, current guidelines on the management of complex renal cysts continue to recommend surgery as the mainstay treatment and suggest that the use of active surveillance should be reserved for select patients.6, 16
This study sought out to assess the adoption of active surveillance in Canada and to examine barriers to more widespread use. We found that approximately one third of Canadian urologists stated that they offered active surveillance as a treatment option in greater than 50% of patients who are diagnosed with a Bosniak III cyst, while only 10% of urologists offered surveillance in the majority of Bosniak IV cases. Importantly, over 60% of urologists did not consider or rarely considered active surveillance as a treatment option for a Bosniak IV cyst. Furthermore, the adoption of active surveillance for both Bosniak III and IV cysts was significantly greater among academic urologists compared to non-academic urologists. Likely reflecting the confidence of urologists for active surveillance, a greater proportion of urologists felt that, when offered to a patient, the chance of surveillance being chosen as management strategy was greater among patients diagnosed with a Bosniak III cyst than those with a Bosniak IV cyst.
When respondents were questioned on potential barriers preventing a more widespread use of active surveillance, the most common perceived concerns were  the lack of data supporting this strategy in this population,  the oncologic safety and benefits of active surveillance and  the lack of guidance on how to perform active surveillance and which specific triggers should be used to recommend discontinuation of active surveillance. We asked respondents what patient and tumor characteristics increased their likelihood of recommending active surveillance. As expected, a number of factors seemed to influence the urologist’s decision, highlighting the fact that treatment decision for Bosniak III and IV cysts is a challenging one. We identified that a personal or familial history of kidney cancer, as well as the patient’s treatment preference, influenced the likelihood that a physician would offer active surveillance. Multiple tumor characteristics also seemed to influence the likelihood of offering surveillance, with the most reported features being cyst size, size of nodular component, and presence of cyst wall nodularity. Importantly, the respondents also identified criteria perceived as triggers to offer discontinuation of active surveillance. For Bosniak III, the most common triggers were progression of cyst on imaging from Bosniak III to IV or development of cyst wall nodularity, and worsening or change in the wall or septa enhancement. For Bosniak IV cysts, the most common criteria identified were growth rate of solid component and overall growth of solid component. Interestingly, for both Bosniak III and IV cysts, the growth of the cystic component was not considered by most urologists as being worrisome enough to warrant treatment.
Although this study offers insight into the current management of complex renal cysts in Canada, it is not devoid of limitations. First, the results are based on Canadian urologists’ perceptions, and the identified criteria for initiation and discontinuation of active surveillance have never been properly studied. Therefore, the reported use of active surveillance may not necessarily be generalized to all clinicians’ real-life practice. The reported patterns of active surveillance may provide a starting point for future studies, but criteria need to be validated before being applied in clinical practice. Second, there might be a selection bias in our cohort, as urologists interested in active surveillance of complex cysts may have responded to the survey more readily.
On the other hand, the study carries several strengths. First, the survey was pilot tested and validated by 20 experts in the field of urology. Second, the response rate to this survey was 24%, which is similar, and even higher than in other Canadian urology surveys.25, 26 Third, this study was designed, conducted and reported according to appropriate recommendations for survey research.19, 20 Most of the questions were structured in a closed format (binary, ordinal, nominal) in order to lower the bias of the responses.