Renal Mass Biopsy: When Is it Justified and What do the Guidelines Say?

Tim McClure, MD, presented on renal mass biopsy this year at the Symposium on Clinical Interventional Oncology (CIO) in Miami, Florida. Dr. McClure is Assistant Professor of Urology and Radiology at Weill Cornell Medical College in New York City, and his CIO presentation discussed biopsy and ablation staging, circumstances in which renal mass biopsy is necessary, and recommendations from guidelines.

Which renal masses should undergo biopsy?

Smaller renal masses (less than 4 cm) are often benign, and most tumors that we ablate are less than 4 cm. A recent study in JAMA  looked at patients undergoing partial nephrectomy, which is different than ablation but generally still involves smaller tumors, and the authors found that approximately 30% of patients had benign tumors.¹ This suggests that 30% of patients are being taken to the operating room for benign tumors. It is surprising to think that almost 1/3 of patients are being taken to the operating room for a benign tumor- this should be avoided.  I think it is important that any small tumor should undergo biopsy, because the prevalence of benign tumors is so high.

Is it better to do a biopsy first and then an ablation?

The timing of biopsy and ablation is somewhat of a gray zone. Ideally, I would prefer to do a biopsy first, followed by an ablation. However, most patients do not like that approach. They tend to view the mass as abnormal and want to treat it immediately. There is no increased morbidity to doing the ablation and biopsy at the same time and the only limitation is that there is a slightly higher risk of a non-diagnostic biopsy.  One study showed doing a biopsy at the same time of ablation brought the diagnostic rate from 98.6% to 84.3%.  Shared decision making is key.  If a patient is willing to take an increased risk of having a non-diagnostic biopsy with ablation and biopsy at the same time, then go for it. The AUA and ASCO guidelines recommend biopsy prior or at the same time of ablation.   

What are some important points to remember from the most recently released guidelines?

The AUA’s and ASCO’s recommendation for biopsy is if the diagnosis will help guide management and should be done prior to or at the same time as thermal ablation.  The AUA also states that biopsy is not necessary in unhealthy patients or in healthy patients in whom management will be surveillance only. 

Do the guidelines most agree, or are there any significant areas of difference?

The AUA and ASCO state that biopsy should be done when biopsy will change clinical management. There is a belief that biopsy is unlikely to change management because many clinicians think that all renal masses should be excised. However, I personally think there should be more of a role for biopsy due to the high prevalence of benign, small tumors that do change clinical management.

Do patients have any objections or fears about biopsy?

Patients sometimes fear that doing a biopsy will spread the tumor, but that has not been reported in recent literature. Patients are also concerned about diagnostic accuracy. There is a perception that diagnostic accuracy is low, but the most recent studies show that accuracy approaches 90% to  95%.

Are there any complications or risks that occur with biopsy?

The biggest concern is having bleeding after the biopsy. However, the risk of bleeding is very low, particularly with image-guided biopsy. There is also the risk of having a non-diagnostic biopsy, but this is low, around 5% to 15%.

What is the role of imaging in performing biopsy?

Classic imaging findings of a renal mass containing fat are diagnostic of an angiolipoma and do not need a biopsy. There are some papers that suggest that it is possible to make an image-based diagnosis of renal cell cancer subtype. However, those studies are of poor quality. Imaging should not be used to make a differentiation between different types of cancer because there is significant overlap in tumor imaging characteristics. It is fine for imaging to make suggestions, but it is not right to use imaging to make a diagnosis. There probably will be a role for imaging in the future, but we are currently not at that point. We might be putting the cart before the horse with regard to making pathologic diagnosis with images.  

What are some other important tips for colleagues?

Biopsy is especially important for patients with bigger tumors for which ablation is not an option, or for patients who are very sick and are not candidates for surgery due to high risk of complications. With these patients, if we find a benign tumor, we can hold off on performing a surgery. I have treated patients who have previously been seen at outside institutions and were recommended to have surgery. After we performed biopsies, some of these patients were treated with ablation or embo-ablation, and others did not need treatment at all. These patients avoided nephrectomies as a result of having a biopsy first.

What are the main takeaways from your presentation?

I want to be sure that everyone understands that the guidelines support the role of biopsy in the management of small renal masses. There is sometimes a lack of understanding from our colleagues in urology regarding the value of small renal mass biopsy, so we have an important role to play in educating them about that value. We can also share our insights into the value of biopsy, and we could potentially help up to a third of patients avoid going to the operating room for unnecessary surgery. From the interventional radiologist perspective, we should ensure that we are ideally performing ablations and biopsies at the same time, or staging the intervention with a biopsy first, followed by an ablation. 

Reference

Kim JH, Li S, Khandwala Y, Chung KJ, Park HK, Chung BI. Association of Prevalence of Benign Pathologic Findings After Partial Nephrectomy With Preoperative Imaging Patterns in the United States From 2007 to 2014. JAMA Surg. 2019;154(3):225–231. doi:10.1001/jamasurg.2018.4602.