Comparison of coaxial technique with sequential (non-coaxial) technique for renal mass biopsy: evaluation of diagnostic efficacy, complication rates, seeding risk, and clinical outcomes.

backgroundRenal mass biopsy (RMB) enables histology-driven management. Guidelines strongly recommend RMB using a coaxial needle to minimize tumor seeding, albeit with a low level of supporting evidence.

objectivesTo evaluate if RMB in small renal masses (SRMs) with the coaxial technique was associated with lower seeding, less upstaging to pT3a, and less cancer-recurrence, compared to RMB without the coaxial technique (sequential technique). MATERIALS AND

methodsRetrospective study of RMB performed between 2004 and 2020, where biopsy-technique information was available. 1174 SRMs were biopsied (coaxial-59%; sequential-41%). Diagnostic yield, complication, procedure-time, seeding, upstaging to pT3a after nephrectomy, and cancer-recurrence were compared.

resultsDiagnostic yield did not differ significantly between coaxial and sequential techniques 87% (600/692) vs. 88% (425/482); p = 0.62. Complication rates were higher for the coaxial technique (31/692 (4%) vs. 10/482 (2%); p = 0.04). This difference was not significant after adjusting for imaging modality used (p = 0.35). There were 2 subjects with tumor seeding (tiny fragments in the perinephric fat beside the renal mass in the resected surgical specimen), one patient with each technique. Both were papillary RCCs and did not recur on follow-up. Of the 414 resected SRMs, 5% (20/414) were upstaged to pT3a after nephrectomy, and did not differ between coaxial and sequential groups (3%,8/231 vs. 7%,12/183; p = 0.14). There was no difference in the positive margins or disease recurrence (p = 0.82, 0.39).

conclusionsRMB with a coaxial needle was not associated with higher yield, lower tumor seeding, lower upstaging, or lower recurrence. Tumor seeding is rare, observed in only two patients with papillary RCC, occurring with either biopsy technique. Due to a lack of evidence for the superiority of one technique, availability and preference may guide the choice of biopsy technique. KEY POINTS: QuestionRisk of seeding after renal mass biopsies (RMB) remains a concern, and the overall risk of seeding and whether the coaxial technique mitigates that risk is unknown. Findings Seeding was exceedingly rare after RMB. There was no difference in seeding, upgrading, or recurrence between sequential and coaxial techniques. Clinical relevanceIt has been suggested that tumor seeding after RMB may be prevented using a coaxial needle. Our results have demonstrated that RMB with or without a coaxial needle is equally safe, and these were not associated with an increased risk of complications, needle tract seeding, or disease recurrence.