Management of complex renal cysts in Canada: results of a survey study

Up to one third of individuals over 60 years of age will be diagnosed with a renal cyst following abdominal imaging [1]. Renal cysts are classified according to the Bosniak classification, which categorizes the cysts according to their degree of complexity and risk of malignancy [2‐4]. Cystic renal cell carcinoma represents approximately 5–10% of all renal malignancies [5]. Bosniak III and IV cysts have a high risk of malignancy (40–60% and 80–90%, respectively) and have traditionally been managed with surgical excision [6, 7]. However, similar to small non-cystic renal masses, there is growing evidence suggesting that most of these cysts are indolent and unlikely to metastasize [5, 8‐15]. Thus, active surveillance has been proposed as an alternative to surgery [6, 16].

Recent observational data has provided support for the use of active surveillance among patients with complex renal cysts [17, 18]. However, the adoption of this treatment strategy for the management of complex cysts in Canada and the criteria used by urologists as triggers for discontinuation of surveillance and intervention have yet to be defined.

The objectives of this survey study were to characterize the use of active surveillance in the management of complex renal cysts in Canada and to elicit the perceived barriers to adoption. We also aimed to characterize patient and disease factors associated with use of active surveillance and triggers used as criteria for intervention.

This is a descriptive cross-sectional study using electronic surveys and conducted based on known guidelines [19, 20]. Following approval from the CIUSSS de l’Estrie - CHUS Research Ethics Board, a pilot questionnaire was developed and tested among 20 urologists in October 2018. All items were then revised according to the feedback received in the pilot survey. The survey questions were formatted as short answer, multiple choice, or Likert rating scale questions. Responses were anonymous and no personal information was collected or stored. An electronic open survey was generated on REDcap™ and distributed via email. The survey was distributed to all active members of the Canadian Urological Association (CUA) with a functional email address. Three emails (one initial and two reminders) containing a link to the English language questionnaire were sent out to all 583 members between October 30 and November 19, 2018. Questions covered practice patterns regarding complex renal cysts, criteria used to select candidates for active surveillance, triggers to intervene in patients on active surveillance, and perceived barriers to a greater adoption of active surveillance (Additional file 1). In analyses, we excluded non-practicing urologists, urologists who reported not managing complex renal cysts, and urologists who gave incomplete demographic information or who did not answer questions beyond the demographic section.

Demographic data are presented in Table 1. Of the eligible respondents, 71 (51.1%) practiced in an academic center, while 68 (48.9%) practiced in a non-academic setting. The majority (87.0%) of respondents reported managing ≤20 new complex renal cysts on an annual basis.

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 [1] the lack of data supporting this strategy in this population, [2] the oncologic safety and benefits of active surveillance and [3] 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.

This study supports that, despite the lack of high-quality evidence, many Canadian urologists offer active surveillance as an option to patients with complex renal cysts, especially if they have a Bosniak III cyst. However, the lack of sufficient data or guidelines on safety seems to prevent widespread adoption of active surveillance. Prospective studies should be conducted to provide evidence on the oncologic safety, benefits, harms, cost, eligibility criteria, and guidelines for the discontinuation of active surveillance in the management of Bosniak III and IV cysts.