Page 2 - Role of renal mass biopsy in the management of kidney cancer: KCRNC

Lavallée et al

risk of progression), and approximately 20% are benign. 8-10 mass biopsy for small renal masses, more patients were sub-
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Common management options include surgical removal mitted to the risks of biopsy. Because both upfront treat-
(partial or radical nephrectomy), thermal ablation, active ment of small renal masses and renal mass biopsy expose
surveillance, and watchful waiting. 11-14 The choice of man- patients to risks, it is important to consider in which patients
agement should be tailored to the patient based on medical renal mass biopsy will influence management.
factors, mass characteristics, and the patient’s values and
preferences. Renal mass biopsy as a diagnostic test
Renal masses >4 cm have a higher probability of being
malignant. 10,15,16 The options for management are fewer com- 2. Renal mass biopsy should include at least 2–3 core
pared to small masses, and most patients with non-metastatic biopsies to sample the mass. Fine-needle aspiration is
disease who are suitable for intervention are counselled to not sufficient.
proceed with surgical removal of the mass. Biopsy of a local- 3. The diagnostic accuracy of renal mass biopsy varies by
ized large (>4 cm) renal mass is not routinely recommended hospital, mass size, mass location, and patient factors.
unless there is clinical suspicion of a non-renal cell carcin- The utility of renal mass biopsy depends on its ability
oma (RCC) mass or abscess. 5,16 to provide a diagnosis of malignant vs. benign histology.
Importantly, renal mass biopsy should include multiple core
Renal mass biopsy to guide clinical decision-making tissue samples (at least 2‒3) using a large bore needle (16‒18
12
gauge) through a coaxial sheath. Core needle biopsies are
1. Renal mass biopsy should be offered to patients with superior in diagnostic ability when compared to fine-needle
a renal mass when the result of the biopsy will alter aspiration of a mass and should be considered standard of
their management. care for renal mass biopsy. 23
Renal mass biopsy is a diagnostic test. Therefore, like Numerous series of renal mass biopsy for small renal
any diagnostic test, it should be performed if the result will masses performed at experienced centers have been pub-
influence management. Historically, almost all medically fit lished, including several with Canadian data. A recent
5-7
patients with a solid enhancing renal mass suspicious for systematic review and meta-analysis including 57 studies
RCC were recommended for surgical treatment to avoid any and 5228 patients reported on the diagnostic characteristics
risk of metastatic spread. It is now known that 20% of small of renal mass biopsy. The overall diagnostic rate was 92%
renal masses are benign and most of the malignant masses (interquartile range [IQR] 81‒97%) and the non-diagnostic
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have low metastatic potential. 9,10,17 In recent years, greater biopsy rate ranged from 0‒23%. Diagnostic rate indicates
understanding of the natural history of small renal masses the percentage of renal mass biopsies that the pathologist
has led to increased use of active surveillance to avoid was able to provide a diagnosis of malignant or benign path-
complications of treatment. 18,19 While surgery for a small ology based on the tissue sampled. A non-diagnostic biopsy
renal mass is usually curative, based on a recent systematic indicates that only normal renal tissue was sampled (i.e., the
review and meta-analysis, complications of surgery occur biopsy missed the mass) or the pathologist was unable to
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in 21% of patients, with 7% of patients having a severe differentiate benign vs. malignant pathology of the mass. A
(Clavien grade 3‒5) complication. A diagnostic test, such true positive biopsy result indicates that the biopsy pathol-
20
as renal mass biopsy, that may safely allow some patients ogy was concordant with the surgical pathology (e.g., both
with benign masses to avoid treatment, is useful. Current showed RCC). A true negative biopsy would indicate that
rates of renal mass biopsy in Canada are not known. 21 there is no malignancy in the mass if the biopsy is benign.
Many studies report rates of biopsy in patients who received Since most series do not remove masses with benign find-
treatment (e.g., surgery), however, these do not account ings on biopsy, the true negative rate is frequently unknown,
for patients who may have received biopsy and avoided and calculation of sensitivity and specificity is limited.
surgery. A Canadian study reported that at centers where The largest Canadian series on renal mass biopsy recently
renal mass biopsy is more frequently performed for patients reported a diagnostic rate of 90% (n=476) for patients with
with small renal masses, there are fewer benign masses a small renal mass. In this series, for patients with a non-
6
surgically excised. In this study, at centers where the renal diagnostic first renal mass biopsy who then underwent a
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mass biopsy rate was 63%, the rate of benign pathology for second biopsy (n=24), 83% had a diagnostic second renal
6
surgically excised masses was 5%. Comparatively, centers mass biopsy. The true positive rate for renal mass biopsy
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with a biopsy rate of 12% had an 11% benign pathology has been reported between 74% and 100%. However, the
7

rate for surgically excised masses. It is, however, unknown concordance between tumor (mass) grade on biopsy and
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if any of the renal masses spared from surgery after biopsy grade on surgical pathology is 62.5% (IQR 52.1‒72.1%). 7
progressed and caused symptoms or were false negative A team of physicians with experience performing and
biopsies. Also, at centers that have higher rates of renal analyzing the results of renal mass biopsies is important.
378 CUAJ • December 2019 • Volume 13, Issue 12