Renal mass biopsy provides actionable information, but only under specific circumstances-yet it is an increasingly necessary part of the nuanced patient discussion.
Some aspects of renal mass biopsy are not controversial. For example, AUA guidelines state that renal mass biopsy should be done prior to any planned ablation procedure, or when a patient presents with a lesion suspected to be metastatic cancer from a different primary source.1
What is currently controversial is how frequently biopsy should be performed, and how often it affects clinical decision-making, according to Robert G. Uzzo, MD, G. Willing “Wing” Pepper Chair in Cancer Research and chair of surgical oncology at Fox Chase Cancer Center, Philadelphia.
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“Some people will say, ‘More information is always better’-it’s safe, it’s informative, and it stratifies risk, so therefore, get the biopsy more often rather than less often,” Dr. Uzzo told Urology Times.
“On the other hand, people will say, ‘It’s not without risk, and there are associated complications,’ ” he added. “It can cause bleeding, infection, and occasionally, significant complications such as pneumothorax, and it is sometimes non-diagnostic or falsely reassuring.”
The most common reason to avoid renal mass biopsy today, according to Dr. Uzzo, is the risk of complications, especially in patients with anatomically complex lesions less amenable to biopsy and those on anticoagulation. Additionally, if the risks of obtaining the information outweigh the benefits and/or if the information obtained is not clinically actionable (eg, the patient or physician won’t accept the uncertainty or test performance characteristics), biopsy can be avoided.
AUA guidelines characterize the complication risk of renal mass biopsy as low. Recent data suggest the most common complications are renal hematoma (4.9%), clinically significant pain (1.2%), gross hematuria (1.0%), and pneumothorax and hemorrhage requiring transfusion in less than 1% of cases.2
Although false negatives and false positives are a potential concern, in practice, core renal mass biopsy has excellent sensitivity and specificity (97.5% and 96.2%, respectively) and a positive predictive value that approaches 100%, studies suggest.
Next: Relatively high non-diagnostic rate of 14%
Perhaps the greater concern is the relatively high non-diagnostic rate of 14%, which patients should be aware of, according to Dr. Uzzo. A biopsy can be non-diagnostic, for example, when renal parenchyma or connective tissue is sampled or if the tumor is in a challenging location.
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“The upper pole, particularly anterior and medial, can be very tricky,” Dr. Uzzo said.
In some cases, tumors can be histologically heterogeneous, which can cause misleading biopsy results.
The non-diagnostic rate can be reduced substantially with repeat biopsy; nevertheless, patients who are young and healthy might not accept the potential uncertainty of a non-diagnostic or false-negative result and instead elect for an intervention, Dr. Uzzo said.
That’s one key reason why current guidelines recommend against renal mass biopsy for patients “unwilling to accept the uncertainties” associated with the procedure, particularly young and healthy patients with decades of future life expectancy at risk. Likewise, the guidelines advise against biopsy in older or frail patients who will be managed conservatively regardless of renal mass biopsy findings.
Active surveillance is a related area of controversy. For patients with small renal masses who are placed on an initial course of active surveillance-who are often elderly or frail-the results of biopsy rarely change the management approach, Dr. Uzzo and colleagues said in a recent editorial.3
Thus, patients whose risk calculations lead them and their physician to an initial course of active surveillance may be able to avoid initial renal mass biopsy as “unnecessary,” unless perhaps the patient has significant anxiety regarding surveillance or the tumor exhibits rapid growth kinetics, the authors said.
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Whether a biopsy is warranted in surgical patients who are young and fit is likewise questionable, given the inherent limitations and risk of biopsy, the authors added. Thus, they recommended “surgery without histologic confirmation” be maintained as the standard of care in this setting.
Next: Tumor seeding, grade concordance
Biopsy or aspiration of cystic renal masses concerning for RCC is not generally advised, according to the guidelines, based on the theoretical concern about the potential for tumor spillage. However, the guidelines also highlight the lack of reported solid RCC tumor seeding cases involving modern biopsy techniques, which usually incorporate a coaxial sheath.
“The possibility of needle track seeding isn’t really a justifiable concern on the large scale, as it’s such an infrequent event,” Dr. Uzzo said.
Tumor seeding was not reported in any of 16 renal mass biopsy studies that were included in a recent review by the Agency for Healthcare Research and Quality (bit.ly/AHRQrenal). That review of potential harms of biopsy represented 2,422 biopsies in studies published between 1997 and 2015.
Grade concordance is one other issue that may give some clinicians pause about renal mass biopsy. The concordance in grade from biopsy to surgically resected tissue is imperfect, particularly with regard to results that suggest low-grade RCC.
It is possible, but not likely, that a biopsy will suggest high-grade cancer when in fact the tumor is low grade; in contrast, the concordance between low-grade biopsy and low-grade tumor is only on the order of 60% to 70%, according to Dr. Uzzo.
“That might be a cause of concern because you might say, ‘I got a biopsy and it was cancer, but it was low-risk, low-grade, so I’ll watch it,’ when in fact, the grade is the least reliable of the metrics on the biopsy,” Dr. Uzzo said.
The bottom line is that the risks, benefits, and limitations of renal mass biopsy must be considered on the whole for each patient to determine whether it’s going to yield actionable information.
“Most of the time, renal mass biopsy provides informative and actionable information with which to make a more informed clinical choice. I don’t think that it’s always necessary, but I think it’s increasingly necessary when having a complex and nuanced discussion with a patient,” Dr. Uzzo said.
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1. Campbell S, Uzzo RG, Allaf ME, et al. Renal Mass and Localized Renal Cancer: AUA Guideline. J Urol 2017; 198:520-9.
2. Patel HD, Johnson MH, Pierorazio PM, et al. Diagnostic Accuracy and Risks of Biopsy in the Diagnosis of a Renal Mass Suspicious for Localized Renal Cell Carcinoma: Systematic Review of the Literature. J Urol 2016; 195:1340-7.
3. Kutikov A, Smaldone MC, Uzzo RG, et al. Renal Mass Biopsy: Always, Sometimes, or Never? Eur Urol 2016; 70:403-6.
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