He began his talk with some important basic data on SRMs (Figure 1). Data have shown that less than 1 cm, the probability of cancer is probably 50%, with bigger masses being more likely malignant, as can be seen in table 1.1
Figure 1 – Typical small renal mass:
Table 1 – Small renal mass sizes and correlation to malignancy:
Next, the role of SRM biopsy was discussed. Traditionally, biopsy was not performed due to several reasons: a) 80% of masses were considered malignant, b) Indeterminate results of the biopsy were common (up to 30%), c) False negative rate was shown in 20-30% of cases, d) It was difficult to distinguish between certain tumors, e) Fear of tract seeding. However, nowadays, we know that treating all SRMs result in 20-30% overtreatment rate (due to benign lesions). Furthermore, 25% of patients with SRMs have preexisting chronic kidney disease (CKD). All these lead to the assumption that incorporating a biopsy can reduce overtreatment. More recently, the technical failure rate of the biopsy has shown to be significantly reduced to 14%.2 The diagnostic accuracy has been demonstrated to be quite high, with 97% sensitivity, 96% specificity, and a false positive rate of 4%. Also, track seeding is exceptionally rare. The current AUA guidelines state that a biopsy for SRM should be performed in anybody whom it would alter management, patients with metastatic disease, lymphoma, or inflammatory or infectious mass. Also, a biopsy should be performed before thermal ablation, and in post thermal ablation tumor recurrence. Core biopsy is always preferred over fine needle aspiration.3 Dr. Clark added that he believes that a biopsy should also be performed in patients considering active surveillance, and in those at a high risk for intervention (solitary kidney, and significant CKD).
Next, Dr. Clark discussed the various treatment options, basically boiling down to surveillance, ablation or surgery. Surveillance was the first option discussed. The mean growth rate of SRMs was originally thought to be almost 0.3 cm/year, with no difference in growth based on the tumor size, with a trend toward faster growth in cancer vs. benign lesions. More recently, the mean growth rate has been shown to be closer to 0.09+/-1.51 cm per year,4 with the growth rate decreasing with time, as shown in figure 2. Importantly, the metastasis rate of SRMs is approximately 0-2%.
Figure 2 – Small renal masses growth rate over time:
The next topic discussed was the option of thermal ablation. Generally, there are two options – radiofrequency ablation (heat up to at least 70 degrees Celsius), and cryoablation (cool to less than – 40 degrees Celsius). There are also two fundamental approaches – laparoscopic and percutaneous. Thermal ablation is minimally invasive, requiring an overnight stay, at most, with low morbidity, and it can be repeated several times. Its biggest advantage is the low complication rate compared to partial nephrectomy.5 Its disadvantages include lower local recurrence-free survival compared to surgery (88-92% vs. 98%), and the long-term efficacy data is available for 3-5 years only, compared to 20 years for surgery.
Next, Dr. Clark discussed the option of surgery (Partial nephrectomy vs. Radical nephrectomy). Historically, every SRM was removed with radical nephrectomy, but in recent years, partial nephrectomy has been the standard of care, either by open, laparoscopic or robotic approach. Similar cancer control and survival rates have been shown in partial and radical nephrectomy.6 However, partial nephrectomy has shown lower rates of postoperative CKD stage 3 when compared to radical nephrectomy.7
Dr. Clark concluded his talk stating that for SRMs renal biopsy is playing an increasing role in select patients. There are several treatment options for SRMs: active surveillance, percutaneous thermal ablation, or surgical removal (preferably partial nephrectomy). Lastly, patient selection and tumor characteristics should drive decision making.
Presented by: Peter Clark, MD, Atrium Health and Levine Cancer Institute
Written by: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre @GoldbergHanan at the American Urological Association's 2019 Annual Meeting (AUA 2019), May 3 – 6, 2019 in Chicago, Illinois
- Frank, Igor, et al. “Solid Renal Tumors: An Analysis of Pathological Features Related to Tumor Size.” The Journal of Urology, www.auajournals.org/article/S0022-5347(05)62810-8/pdf..
- Patel et all. “Subtyping the Risk of Intermediate Risk Prostate Cancer for Active Surveillance Based on Adverse Pathology at Radical Prostatectomy.” The Journal of Urology, www.auajournals.org/article/S0022-5347(18)42985-0/abstract.
- Campbell et al. “Renal Mass and Localized Renal Cancer: AUA Guideline.” The Journal of Urology, www.auajournals.org/article/S0022-5347(17)59870-5/fulltext.
- Uzosike et al. "Growth Kinetics of Small Renal Masses on Active Surveillance: Variability and Results from the DISSRM Registry," The Journal of Urology, 2018 March, doi: 10.1016/j.juro.2017.09.087
- Rivero JR, De La Cerda J 3rd, Wang H, Liss MA, Farrell AM, Rodriguez R, Suri R, Kaushik D. “Partial Nephrectomy versus Thermal Ablation for Clinical Stage T1 Renal Masses: Systematic Review and Meta-Analysis of More than 3,900 Patients,” J Vasc Interv Radiol. 29, 1 (Jan 2018):18-29. doi: 10.1016/j.jvir.2017.08.013.
- Van Poppel H. et al. "A Prospective, Randomised EORTC Intergroup Phase 3 Study Comparing the Oncologic Outcome of Elective Nephron-Sparing Surgery and Radical Nephrectomy for Low-Stage Renal Cell Carcinoma," European Urology, April 2011, https://doi.org/10.1016/j.eururo.2010.12.013
- Campbell et al. "Renal Mass and Localized Renal Cancer: AUA Guideline," The Journal of Urology, 2017 Sept, doi: 10.1016/j.juro.2017.04.100