CUOS 2019: Biopsy of the Small Renal Mass - Still Controversial?

Toronto, Ontario ( Dr. Tony Finelli presented on the topic of biopsy of small renal masses. There are common arguments against the routine use of renal tumor biopsy, made by physicians and patients alike.  Dr. Finelli addressed each one of these comments during his talk. The first argument is that many physicians state that they know it is a kidney tumor and there is no point in biopsying it. First, it is important to recognize that many times lesions that are “in keeping with renal cell carcinoma (RCC)” are in fact benign on final pathology. Kidney cancer is a very heterogeneous disease (figure 1), and up to 25% of all small renal masses are benign.1 Additionally, Oncocytomas appear similar to clear cell RCC2, and papillary tumors are less contrast-enhancing tumors than clear cell RCC, but this is not 100% predictive.

Figure 1 - Kidney Cancer is a Heterogenous Disease:
UroToday CUOS19 Kidney Cancer is a Heterogenous Disease
The second argument is that renal tumor biopsy isn’t safe. In a systematic review and meta-analyses of the diagnostic accuracy of percutaneous renal tumor biopsy, it was shown that major complications occur in <0.1% of cases, transfusion rates are prevalent in less than 0.1% of cases, and seeding has occurred in previous cases, but this is extremely rare.3 The overall complication rate in the meta-analysis was 8.1%, but only 3 Clavien grade 2 complications were noted, while the rest were grade 1. Hematomas were reported in 4.3% of cases. Only one case of pneumothorax was reported, and only one case of seeding was demonstrated. Seeding is truly rare and is not a real concern that should deter us from performing a biopsy.

The next argument discussed is that small renal mass biopsy isn’t accurate. According to the meta-analysis mentioned earlier3, the diagnostic rate of the biopsy is 90%.3 If repeat biopsies are attempted, their diagnostic rate is even higher (+90%).4 A total of 57 studies were included in this review3, with over 5000 patients. The sensitivity and specificity of diagnostic core biopsies and fine needle aspiration were 99.1% and 99.7%, and 93.2% and 89.8%, respectively.3 Overall, 14 studies reported the concordant tumor histotype between renal tumor biopsy and final surgical pathology. The median concordance rate was 90.3%. In a paper by Richard et al., 496 renal tumor biopsies were described, with more than 26% of them were benign, with 61% of the benign tumors being oncocytomas, and 27.5% - fat poor angiomyolipoma.5 The initial biopsy was diagnostic in 90% of cases. Following renal tumor biopsy, among the malignant lesions, there was an excellent agreement between biopsy and surgical histology subtypes (Kapp 0.88, 95% CI 0.81-95). For clear cell RCC, there was also good agreement between disease grades when pooled in low and high grades (kappa 0.8, 95% CI 0.48-0.92).

The next argument discussed, was that the biopsy wouldn’t change the expected treatment. This is however not true, as most benign diseases do not require treatment, and a diagnosis of biopsy could help avoid unneeded surgery. There is also emerging evidence of variation in malignant potential of histologic subtypes. Lastly, all treatments can potentially carry morbidity. Recently, a study was published comparing 30-day readmission rate in patients who underwent open partial nephrectomy, minimally invasive partial nephrectomy, and minimally invasive radical nephrectomy. More than 5000 patients were analyzed. The 30-day readmission rate was 5.9% for open partial nephrectomy, 4.5% for minimally invasive partial nephrectomy and 6.1% for minimally invasive radical nephrectomy. These are not insignificant numbers and should be considered. If we can avoid unnecessary surgery, we can prevent morbidity.

Recently, a retrospective multicenter study of patients who underwent partial or radical nephrectomy was published.6 In this study, all patients had contrast-enhancing lesions <4 cm. A logistic regression model was used to examine whether the odds ratio of obtaining a benign tumor following surgery differed between centers that routine favor renal tumor biopsy and centers where a selective renal tumor biopsy approach is used. A total of 542 small renal masses in 516 patients were included in this study, and the rate of the benign tumor was 11%. This was significantly lower at centers that routinely favor renal tumor biopsy than at centers where a selective renal tumor biopsy approach is used (5% vs. 16%, p<0.001). Compared to centers that routinely favor routine renal tumor biopsy, the odds of finding a benign tumor after surgery was four times more likely at centers where a selective renal tumor biopsy approach is used (OR 4.1 95% CI 1.9-8.3). In as of yet unpublished probabilistic sensitivity analysis, the number needed to biopsy to avoid one nephrectomy was found to be 9.9, with 0.0005 false positive diagnoses (benign tumors), and 0.13 false negative diagnoses (malignant disease).

In summary, a renal tumor biopsy is accurate, safe, impacts management, avoids over-treatment and enables personalized care for each patient. Its utilization and incorporation as the standard of care should become a reality according to Dr. Finelli.

Presented by: Tony Finelli, MD, MSc, FRCSC, Chief of Urology, University Health Network, GU Site Lead, Princess Margaret Cancer Center, Associate Professor, University of Toronto, Ontario, Canada

Written by: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre, Twitter: @GoldbergHanan at the CUOS – Canadian Uro-Oncology Summit 2019, #CUOS19 January 10-12, 2019 Westin Harbour Castle, Toronto, Ontario, Canada

1. Frank et al. J Urol 2013
2. Miller et al. Roentgenolog 2011
3. Marconi L et al. Eur Urol 2015
4. Leveridge et al. Eur Urol 2013
5. Richard et al. Eur Urol 2015
6. Richard PO et al. J Urol 2018,