AUA 2023: Panel Discussion: Small Renal Mass Management

(UroToday.com) The first day of the American Urological Association had a panel about the management of small renal masses (i.e., renal cancer with < 4 cm, also known as T1a). The session was moderated by Dr. Stuart Wolf, also had Dr. Antonio Finelli discussing active surveillance, Dr. Jodi K. Maranchie discussing ablation, and Dr. Monish Aron discussing partial nephrectomy.

The presentation by Dr. Antonio Finelli brought the evidence regarding Active Surveillance for small renal masses. Initially, he presented the meta-analysis by Chawla et al., published in The Journal of Urology in 2006, in which the natural history of renal tumors was growing 3mm in average yearly. Starting with this information is very important, as it allows for a safe imaging follow-up, and the whole rationale behind active surveillance for small renal masses.

He then presented many studies with long-term data regarding the safety of active surveillance. A multi-center study had a 1% metastasis rate; one study with 497 patients had a five-year cancer-specific survival of 100% in the active surveillance group. Another study showed that the median growth rate was 1.9mm/year for patients with localized renal masses in active surveillance. Dr. Finelli presented a good amount of long-term evidence to show the safety of active surveillance, which is the basis for the AUA, NCCN and EAU guidelines including active surveillance as an option for small renal masses.

The second point of his presentation was regarding active surveillance for complex renal cysts. A study by Alrumayyan et al. published this year showed that active surveillance is feasible for cysts classified as Bosniak III and IV. Another study with 336 patients with a median follow-up of 67 months had only one cancer-specific death (a patient that refused treatment), which represented 0.3% of the sample in a population in which only 30% of Bosniak III and 62% of Bosniak IV underwent (ablative or surgical) intervention.

The third point of his talk was regarding the role of renal mass biopsy. There is a good amount of evidence regarding the benefits of small renal masses, demonstrating a diagnostic rate of over 90% with >99% sensitivity and specificity. But someone might be asking what is the role of renal biopsy? Dr. Finelli explained very simply: to avoid treatment. I would like to point out this fact: over treatment of small renal mass is a significant problem, as upward of 20% of pathological specimens of nephrectomy for T1a tumors have benign histopathology. Dr. Finelli was very precise and meticulous in presenting the importance and the benefits that a renal mass biopsy brings in the decision-making.

The fourth point was regarding the histopathology of benign lesions. Angiomyolipoma were operated in 5.6% in the cases, but Dr. Finelli suggested initial surveillance for “all" asymptomatic cases. Renal neoplasms with oncocytic features are also safe to observe. Also, the histopathology is directly associated with small renal mass growth, as clear cell carcinoma has a significantly higher growth rate compared to chromophore and papillary tumors. All those information came from their experience with biopsy, which, accordingly to him, avoided many un-needed surgeries.

The fifth point of his presentation as regarding the possible risks of active surveillance, in which he responded what is would be: metastasis. However, he showed a meta-analysis by Smaldone published in 2012 including 880 patients with 936 masses in which there were 18 metastases. Factors associated with metastasis were increased age, initial tumor diameter and linear growth rate. Two important factors in this are that in this meta-analysis, the initial tumor diameter which was associated with metastasis was 4.1cm vs. 2.3cm for patients who did not metastasize. However, a 4.1cm is not a small renal mass anymore! Also, very importantly, patients who metastasize had a linear growth rate of 0.8cm/year compared to 0.3cm/year in those who didn't metastasize; therefore, the linear growth is an important factor for following those patients.

Very importantly - he showed his principles on how to conduct active surveillance. He recommended a follow-up every 4 months in the first year, then every 6 months up until 5 years of follow-up, based not only on ultrasound, and associated with axial and chest imaging. Regarding management, he recommended to assess factors regarding the host (comorbidities, renal function, anatomy), the tumor (location, size) and surgeon reasons.

He ended the presentation showing the guidelines that support active surveillance. Accordingly, to him, active surveillance should be recommended for cystic lesions (even most Bosniak IV), for angiomyolipoma, and for all SMR under 2cm. Renal mass biopsy can direct care for small renal masses between 2-4cm. “If you only have a hammer, you tend to see every problem as a nail”.

Dr. Maranchie presentation for ablation therapy for small renal mass was very interesting. She showed the types of ablation, but focused on either radiofrequency or cryoablation, which are the two most commonly used. She presented a summary of the AUA guidelines recommend ablation practices, with prior biopsy, done percutaneously, either with radiofrequency or cryoablation, only for mass with < 3 cm. One might be asking: why is the guideline recommending 3cm as a cutoff for ablation if the definition of small renal mass is 4cm? Well, Dr. Maranchie showed in her presentation the difference between outcomes depending on the site, with a 99% success in single ablation for tumors <2.5cm, an 88% success for tumors 2.5 - 2.9cm (which increased to 96% with two ablations), and a significantly lower success for tumors with >3cm (73% and 78% for single or repeated ablation).

She presented the evidence regarding the potential benefits and complications of ablation therapy. The potential benefit would be a better renal function (compared to partial nephrectomy). However, she then showed a meta-analysis by Patel (2017) with showed no statistical significance difference in renal function when comparing partial nephrectomy or ablation. For complications, she presented a paper by Atwell et al. (2016) in which they had a major complication rate of 7.7% for cryoablation (mostly related to hemorrhage) and 4.7% for radiofrequency (mostly related to urothelial injury).

Going accordingly to the presentation by Dr. Finelli, she also presented the benefits of renal mass biopsy: the 5-year disease free-survival for papillary tumors that underwent ablation was 100% compared to 90% for clear cell carcinoma.

Lastly, she presented the main risk of ablation: recurrence, metastasis and death. A paper by Johnson showed a 81.5% disease-free rate and 94% cancer-specific survival for radiofrequency in a 10-year follow-up. However, she also pointed out that nothing is without drawbacks. However, and very importantly, even defending ablation, she brought all the evidence, even when it was possibly negative: a SEER database showed a 2-fold increased risk of cancer-specific mortality for thermal ablation compared to partial nephrectomy.

Her conclusions were that ablation is feasible, with a low risk of major complications and that most recurrences can be salvaged with repeated treatment. She pointed out that there is indeed a size limit for ablation, which must be respected to achieve equivalent efficacy as other modalities of treatment. However, she pointed out that there is indeed a small increased risk of cancer-specific mortality when patient undergo ablation therapy. 

Partial Nephrectomy - Dr. Monish Aron

The last panelist to speak was Dr. Monish Aron, defending the most commonly performed procedure for small renal mass: partial nephrectomy (71% in 2015). He, however, in the beginning addressed that both active surveillance and ablation have indeed their role on small renal mass management; however, in his opinion, partial nephrectomy is the one treatment which is suitable for most patients, being versatile and broadly applicable.

He then proceeded to bring his principles for a good partial nephrectomy. His main focus is a complete and clean tumor excision, as either can significantly impact the patient outcome, with either local recurrence or metastasis. Secondly, the importance of meticulous hemostasis. His mantra is “I don’t want to see any red blood cell after a partial nephrectomy”.

Then, he presented many technical differences regarding ischemia, resection, reconstruction, approaches, ports, etc. He performs mostly partial nephrectomy with warm ischemia, doing an enucleo-resection, with precision suturing and a cortical renorrhaphy. He used both the transperitoneal and retroperitoneal approach, depending on the location of the tumor - specifically for postern-medial tumors, he prefers to do them retroperitoneally. A high-quality, multiphase CT scan is always performed before surgery, but he emphasizes the benefits of always performing a intraoperative ultrasound also, as some tumors can be missed. He performs arterial clamps for most tumors, sometimes with the help of indocyanine, while also using combined arterial and vein campling for deep tumors with large contact area. Also, the exposure must be maximum to allow for a good resection and reconstruction: “don’t work in a hole”. The placing of sutures must be parallel to the interlobar arteries, with “judicious depth” (i.e. not too deep, in order not to compromise the blood supply, not too shallow, to be effective).

Then, he finalized his presentation showing why he prefers partial nephrectomy for most patients with T1a: the best oncological outcome with the best renal function and similar overall complications.

Conclusions:

• Renal mass biopsy should be performed for most, if not all, small renal masses.
• Active surveillance is safe, especially with the additional information of the biopsy. Even Bosniak IV cysts can be observed.
• Thermal ablation has its role for the management for renal masses with less than 3cm; however, there is indeed a higher risk of cancer-specific mortality which must be discussed with patients.
• Partial nephrectomy is the main intervention (when the patient has an aggressive malignant histopathology in the biopsy), as it has the best oncological outcome without any additional risks.

• Antonio Finelli, MD, University of Toronto
• Jodi K. Maranchie, MD, University of Pittsburgh School of Medicine
• Monish Aron, MD, Keck School of Medicine of USC