How renal mass biopsy impacts management
At the 2015 Society of Urologic Oncology annual meeting in Washington, J. Stuart Wolf, Jr., MD, addressed concerns about the diagnostic inaccuracies of core renal biopsy in the diagnosis of small renal masses.
In his presentation, Dr. Wolf argued, “Biopsy does not need to perfectly identify histologic type and grade when it is paired with a risk-stratified, sized-based management algorithm.”
In a study conducted at the University of Michigan, Ann Arbor, where Dr. Wolf is professor of urology, investigators considered an approach that combined core biopsy risk stratification with an algorithm based on size (J Urol 2013; 189:441-6). To test reliability of the approach, the authors compared the treatment assignment (surveillance vs. excision) in 151 patients based on size and biopsy histology with the appropriateness of that assignment as determined by final pathology after surgical excision. Dr. Wolf demonstrated that use of renal mass biopsy, combined with a size-based management algorithm, has an excellent positive predictive value (100% in that study) but an imperfect negative predictive value (86%).
The combination of renal mass biopsy with a size-based management algorithm was also applied to a multi-institutional database compiled by active robotic partial nephrectomy surgeons (J Urol 2014; 192:1337-42). In that study, the authors concluded that about half the patients theoretically could have avoided surgery had the algorithm, which incorporates both size and biopsy histology, been applied preoperatively.
“The greatest liability [of incorporation of renal mass biopsy in treatment decisions] is false negatives,” Dr. Wolf conceded. He noted that, in his updated series, 17% of patients would have been incorrectly assigned to surveillance, and in fact harbored worse pathology than suggested by biopsy. He was reassured, however, that those patients who underwent delayed intervention had similar rates of partial nephrectomy and adverse pathology when compared with those patients who underwent early intervention.