The Role of Renal Tumor Biopsy
LONDON—With a growing number of small renal masses being detected, renal tumor biopsies should be performed more frequently, a urologist skilled in the technique told attendees at the Renal and Bladder Cancer 4th National Conference.
Neil Barber, FRCS, Consultant Urological Surgeon at Frimley Park Hospital, Surrey, U.K., spoke about his experience of the role of renal tumor biopsies. “Of course the concept of taking a biopsy is not a new thing, we have been doing this for many years,” he said. Biopsy already has an established role for an inoperable mass, a lymphoma, an abscess or an infective lesion.
“The traditional approach to a renal mass is to chop it out, which is quite an unusual approach as you wouldn't think about doing that with prostate cancer,” Dr. Barber said. “With small renal masses we typically use CT [computed tomography] scan, MRI [magnetic resonance imaging] scan, and contrast-enhanced ultrasound to decide what we are going to do.”
These approaches, however, provide insufficient information. “Surely, when dealing with a tumor it would be good to know if it is benign or malignant, what the grade might be, and what the histological subtype might be. These things might influence how a mass might behave and that may influence what treatment options we may offer the patient: surveillance, ablation or partial nephrectomy.”
Previous studies have consistently found that 25%-30% of small renal masses are benign and 65% are low-grade tumors. High-grade tumors are quite rare. “What is really changing everything is the arrival of the small renal mass. I don't think seven or eight years ago we could really see the tsunami of small renal masses that have come our way; it has gone from being a minor part of what we might to do, to a predominant part of what we do.”
Dr. Barber addressed the typical concerns with biopsy: safety, accuracy, and complications of bleeding and seeding.
“From a safety point of view, [and with regards to bleeding] biopsy needles have changed and there is much more confidence on that front,” he explained. “With regards to accuracy, we now have specialist interventional radiologists who are increasing our confidence in the procedure. We also now have specialist pathologists who are getting more accurate and reliable answers to what the mass might be, and this is all leading to the urologist who is dealing with the patient being more confident about the intervention they decide on.”
Dr. Barber questioned whether the accuracy of biopsy diagnosis really matters. Knowing whether the tumor is grade 1, 2, 3, or 4 is not that important. Knowing whether it is low grade or high grade is more important in managing the patient.
Seeding has always been a concern, but Dr. Barber pointed out that since 2001 there have only ever been six cases of reported seeding and no more cases since then. “So we can really put that one to bed.”
So, what are the predictive factors for which tumors are good for biopsy. “One thing is size. The bigger the tumor, the greater the accuracy,” he said, “the smaller the tumor the greater the chance there may be some error on that biopsy.” With regard to solid tumors versus cystic tumors, studies favor solid tumors for biopsy.
Tumor location is also a factor. “The anterior upper pole lesions are more difficult to biopsy than lower pole posterior lesions,” he stated.
As for patient characteristics, patients should be able to lie still long enough to obtain a CT scan. Obesity also is a concern because it could hinder access to the tumor.