Renal mass biopsy safe, but when is it necessary?

“Journal Article of the Month” is a new Urology Times section in which Badar M. Mian, MD (left), offers perspective on noteworthy research in the peer-reviewed literature. Dr. Mian is professor of surgery in the division of urology at Albany Medical College, Albany, NY.

The risk of bleeding complications is probably the most concerning adverse event following renal mass biopsy, which is further amplified by the common use of anticoagulant and antiplatelet medications in the general population. According to a recent study conducted by Posielski et al, the risk of such complications following renal mass biopsy is quite low, even in the presence of low platelets, mildly elevated international normalized ratio (INR), or continued use of aspirin (J Urol 2019; 201:1080-7).

The study authors retrospectively analyzed 1,155 renal mass biopsies performed in 965 patients at a single institution from January 2000 to December 2017 to determine the diagnostic yield and complication rate. Non-diagnostic biopsy result was defined as all cases in which histologic diagnosis of cancer could not be made due to insufficient tissue, necrosis or fibrosis, or normal tissue. Their institutional guidelines allowed biopsy in patients with an INR of 2.0 or less or a low platelet count (25,000-160,000) or continued use of aspirin.

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Mild coagulopathy (INR 1.2-2) was present in 5%, low platelet count (<160,000) was noted in 15%, and aspirin was continued in 38% of patients at the time of biopsy. A total of 745 patients (64.5%) were diagnosed with cancer. Presumably, the other 35% had either non-diagnostic biopsy or benign tumors. The authors do not report the incidence of benign tumors or the indications for biopsy of the larger tumors (4-7 cm).

Biopsy-related complications seen in 2.2%

Of the 965 patients who underwent renal mass biopsy, 24 patients (2.2%) were identified with biopsy-related complications within 30 days, including symptomatic hematoma (0.5%), gross hematuria (0.7%), pain requiring intravenous narcotics (0.3%), urinary tract infection (0.3%), and hypotension, pseudoaneurysm, and urinary retention in one patient each.

Hospital readmission was required for 11 patients (1.0%), and major complications requiring a secondary procedure were identified in five patients (0.4%). Selective renal arterial embolization was needed in two patients and percutaneous abscess drainage was required in one patient. Two patients were admitted to intensive care for urosepsis.

The complication rate for biopsy with three or more needle cores and one needle core was 3% and 1.3%, respectively, but it was statistically insignificant. The use of aspirin (38.1%), mild elevation of INR (4.9%), and somewhat low platelet count <160,000 (15.2%) were not associated with increased risk of hemorrhagic complications. Of note, the dose of aspirin (81 mg or 325 mg), which has a definite impact on risk of bleeding, was not reported.

The complication rates among the 12 radiologists-who each performed at least 50 biopsies-ranged from 0% to 3.6%, which was statistically insignificant.

However, there was a significant variation in the rate of non-diagnostic biopsies among these radiologists, especially for masses <4 cm, ranging from 8.5% to 27.5% (p=.02).

Overall, non-diagnostic biopsies were noted in 145 cases (14.6%). The non-diagnostic biopsy rate was highest for cystic versus solid lesions (40.8% vs. 10.6%, p<.001).

For lesions ≤2 cm in size, about 21% of the biopsies were non-diagnostic. Interestingly, in 80 patients who underwent repeat biopsy due to initial non-diagnostic biopsy, there was no increase in the cancer detection rate in the second biopsy and the non-diagnostic rate also did not change.

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The oft-stated reason to perform renal mass biopsy is to obtain actionable information that can potentially affect the clinical management (ie, surgery versus surveillance). Yet, most studies showing the safety and accuracy of renal mass biopsy do not give any details about which, if any, actions were modified by the biopsy results.

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For small renal masses, should the default position be extirpation unless a clearly benign tumor is detected? Can the small renal masses not be observed without a biopsy? Should a mass with a non-diagnostic biopsy be viewed as being free of cancer and be placed under surveillance? Often, there are important patient-related factors (age, comorbidities, etc.) that supersede the biopsy results during the clinical decision-making process.

While the safety and feasibility of the renal mass biopsy procedure has been established, if or when to obtain the biopsy remains a topic for active discussion. The low complication rate cannot replace the careful appraisal of the necessity and value of biopsy results in the management of an individual patient