Uhlig A, Lenis AT, Wang X et al: Sequencing of renal mass biopsy and ablation: results from the National Cancer Database. Urol Pract 2021; 8: 555.

During the last few decades, technical advances in radiologic imaging and growing use of cross-sectional imaging have led to more frequent incidental detection of small renal masses, which in turn has led to stage migration. Now over half of the renal cancer diagnoses are made at stage cT1a and are therefore amenable to various treatment options.

Renal mass biopsy has traditionally been omitted from the management strategy for most urologists but has increased in recent years to now account for up to 15% of small renal masses.¹ One area in which renal mass biopsy has continued to have a role is in the context of thermal ablation, which now is used as the primary management option in about 10% of cases.² Most clinical guidelines support a renal mass biopsy in patients undergoing thermal ablation in order to determine histology to guide surveillance. However, most guidelines so far do not discuss the timing of the biopsy, whether it should be performed prior to an ablation with an office discussion, or in the same session as the lesion treatment during the thermal ablation itself.

A “one-size-fits all” approach may not be possible due to patient preference regarding treatment, challenges and costs associated with several procedures, and the frequent need to stop required medications with interventions. A staged renal mass biopsy approach could spare some patients unnecessary treatment, as treatment of a benign tumor may often be unnecessary. However, some patients wish to pursue treatment regardless of histology due to the uncertainty of surveillance and desire to avoid lifelong imaging. Despite improvement in histologic subtyping and the widespread availability of useful immunohistochemical stains, the unwillingness of many pathologists to call some indolent lesions benign further limits the role of pre-treatment biopsy guiding management based on histology in a subset of patients.

Understanding the safety of staged vs concomitant renal mass biopsy can inform clinicians on the optimal approach to individual patient care. While a second anesthetic could impact patient health and safety and post-biopsy bleeding can delay thermal ablation, there are some technical challenges with concomitant ablation that can influence safety as well. Bleeding prior to probe placement may obscure lesions, and occasionally a more limited biopsy is necessary due to navigating multiple pre-placed probes. Thus, it is not surprising that the rate of successful histologic diagnoses is reduced.³

Figure. U.S. geographic variability in the utilization of concomitant and staged renal mass biopsy.

In our analysis of the National Cancer Database,⁴ we set out to review utilization, trends and safety with staged vs concomitant renal mass biopsy with thermal ablation. While 46% of ablated tumors had a staged biopsy during the study period, there has been a noticeable shift in the field toward fewer concomitant biopsies in recent years. Interestingly, age and comorbidity did not appear to significantly impact the biopsy approach, but what was associated was histology, size, laterality, insurance status and facility location (see table). The geographic practice patterns greatly differed, with staged renal biopsy approaches ranging from 37.5% to 70.7% depending on the location (see figure). While nearly half of the thermal ablations were performed in an outpatient setting, an increased number of concomitant biopsies required an impatient stay (58.9% vs 41.1% for staged biopsy), which remained significant (OR=1.42, p <0.001) despite controlling for possible confounding factors. Unplanned readmissions were also more frequent with concomitant biopsy (2.5% vs 2.1%), which also remained a significant predictor in multivariable analyses (OR=1.55, p=0.022).

Helping clarify the uncertainty in this area, the most recent AUA 2021 guidelines published a new statement regarding biopsy and ablation. The panel reinforced the importance of obtaining tissue to guide surveillance. However, with this addition, the panel made more formal recommendations on timing and suggest the staged approach is preferred. With the level of evidence based only on “expert opinion,” the panel suggested that decisions on timing be made on an individualized basis.⁵ With very limited data in this area, our work may help inform health care providers to identify the optimal practice for their respective patients. However, further work should aim to assess overall cost and complications with both treatment strategies.