Accepted anatomic concepts that lend to tumor enucleation:
1. A tumor pseudocapsule separates most tumors from renal parenchyma
2. A perfectly executed tumor enucleation should have no renal parenchyma and an intact capsule
3. The volume of tissue submitted for tumor enucleation (TE) will be less than traditional partial nephrectomy (TPN).
However, the terms for TE are varied – and therefore suggest variations in how the procedure is done! This may account for differences in outcomes. But, standardized methods for reporting TE are emerging – and may help address this issue (ie. Renal tumor capsule invasion score, SSA, etc.).
Multiple studies have now demonstrated that TE:
1. Has lower operative time and blood loss than TPN
2. No loss of renal units
3. No difference in major medical and surgical outcomes
4. Low urine leak and bleed rates
These suggest that TE is safe – and may even widen the indication for nephron sparing surgery to more complex renal masses.
In terms of oncologic outcomes:
1. There was no difference in 5 and 10-year progression-free survival regardless of technique
2. There was no difference in CSS or local recurrence rates between groups in multiple studies
3. Margin rates – Dr. Boris argued that while margin rates were higher for TE (17% vs. 0% TPN), positive margins in TE cases are fundamentally different – they are margins at the edge of the tumor rather than margins at the edge of normal tissue. So while margin rates were higher, they don’t translate to worse oncologic outcomes. He considers TE to be a “microscopic margin” technique. He feels that they are less likely to have macroscopic margins than TPN.
However, there is no RCT yet supporting TE over TPN. But there isn’t for any other established urologic procedures either – robotic prostatectomy, laparoscopic radical nephrectomy, etc. Yet, these are now the standards!
His conclusions:
CON: E. Jason Abel, MD, argued against TE, primarily based on oncologic merit.
It has been established on systematic review to have more positive surgical margins (Cao et al. 2017). This is high-quality data demonstrating higher PSM rates. Yet, when translating that to recurrence, there is little high quality data on which to make any strong statements – so saying that high PSM doesn’t translate to high recurrence rates is inappropriate.
He cited Halstedian principles of complete tumor resection as a basic tenet of oncologic management – and that TE fails in that regard.
Ultimately, oncologic outcomes trump ease of procedure, nephron sparing, etc.
He also spent some time on the concept of pseudocapsule. Azhar et al. (JU 2015) noted that 22-49% of tumors had pseudocapsule invasion – so it is not a clear endpoint to tumors. Complete invasion in 22% of tumors was associated with higher T-stage tumors and higher grade tumors – so higher risk tumors are potentially being left behind as positive surgical margins.
Additionally, many of the papers that were cited regarding low recurrence rates after TE had a very short follow-up. Insufficient for oncologic outcomes. As such, the right oncologic procedure is a traditional partial nephrectomy with a rim of normal renal parenchyma.
Debaters:
Pro: Ronald Boris, MD, Indiana University
Con: E. Jason Abel, MD, FACS, University of Wisconsin
Read the First Debate: Active Surveillance for Large Renal Masses is Appropriate
Read the Third Debate: Adjuvant Therapy for High Risk RCC Should Be Used
Read the Fourth Debate:10 years of Big Data Have Changed Renal Cell Carcinoma Management
Written by: Thenappan Chandrasekar, MD, Clinical Fellow, University of Toronto, | twitter: @tchandra_uromd at the 2018 AUA Annual Meeting - May 18 - 21, 2018 – San Francisco, CA USA