**5.3. Managing complications**

or indeterminate pathology [15]. Performing RTBs prior to ablative techniques can also be used to stratify patients—where those with unfavorable histology can be triaged to surgery

In order to facilitate the shift in managing SRMs (be it in AS, RFA or systemic treatment), it is important for us to address these barriers in adopting RTBs. We will now assess the reliability

RTBs are performed percutaneously under local anesthesia. It can be with needle core biopsy

Core needle biopsies yield a higher diagnostic rate and a more accurate histological examination over FNA. This was exemplified by a systematic review performed by Marconi et al. [17] (57 studies recruiting 5228 patients)—showing superior sensitivities and specificities over diagnostic FNAs. A coaxial technique allows multiple biopsies to be taken through a coaxial canula, avoiding potential tumor seeding. Comparing needle sizes used, 18-gauge needles are preferred over 14- and 20-gauge needles—showing safer and more accurate histological

With regard to imaging modalities, US and CT possess their own merits. CT has the advantage of a better resolution that is ideal to locate lesions that are in proximity to critical structures. US has the advantage of lower radiation and lower cost. More importantly it allows real-time

In spite of acknowledging preferred techniques of RTBs, there are other technical factors that affect their success: amount of adipose tissue in the patient, echogenicity and location of lesion. The challenge of performing a successful biopsy can thus vary from lesion to lesion. Effective communication between the interventional radiologist and urologist is necessary to

Recent literature lends support to the diagnostic accuracies of RTBs, challenging the notions some urologists believe. The meta-analysis performed by Marconi et al. [17] showed that initial RTBs yielded a diagnosis in >90% of cases. Core biopsies showed a high sensitivity and specificity of 99.1 and 99.7%, respectively. In cases where both a RTB and surgical pathology were available, good concordance (k = 0.683) for tumor histotype and fair concordance

A systematic review by Patel et al. [21] (including 20 studies with 2979 patients) showed a high diagnostic accuracy of RTB with a sensitivity of 97.5% and a specificity of 96.2%. There

instead.

**5. Addressing barriers**

114 Evolving Trends in Kidney Cancer

and improvements of RTBs.

results [18, 19].

**5.2. Improvements in accuracy**

(k = 0.34) for tumor grade were shown.

**5.1. Improved techniques for biopsy**

or fine needle aspiration (FNA) with US or CT guidance.

needle placement that is suited for nonfocal renal lesions [20].

ensure that a RTB would be reliable in managing a specific SRM.

Reported concerns regarding the safety of RTBs stem from the risks of bleeding, pneumothorax and tumor seeding [7]. Rising literature appraising the choice of gauge needles, imaging modality and preference for core biopsies over FNA have improved the safety of RTBs.

In Patel's et al. study [21], complication rates observed were quite low. The rate of haematomas was 4.9%, while the occurrence of any clinically significant pain was 1.2%. Pneumothorax was only detected in 0.6% of cases, and no study reported any cases of tumor seeding. In Marconi's et al. study [17], the median complication rate was 8.1% with only three Clavien grade ≥2 complications to be reported.

Tumor seeding along the needle tract is anecdotal and very rare. As per the EAU reported guidelines, to avoid any such complication, coaxial sheaths should be used. This allows multiple passes through the renal mass with only one through surrounding tissue.

#### **5.4. Discerning tumour heterogeneity**

Despite the high concordance rates in identifying tumor subtypes (as mentioned above), the heterogeneous nature of RCC in itself is an identified barrier in adopting RTB. It is essential for clinicians to identify the challenges in discerning between specific tumor subtypes in order to have a comprehensive grasp on the reliability of a RTB.

The four main subtypes of RCC include clear cell RCC (**ccRCC**), papillary RCC (**pRCC**), chromophobe RCC (**chRCC**) and collecting duct carcinoma (**CDC**). There are over 10 such subtypes with many inherited syndromes [23]. Each subtype is associated with its own prognostic factors from clinically indolent (pRCC type 1, chRCC) to highly metastatic (pRCC type 2 or ccRCC). Thus, it is valuable for a subtype to be distinguished from benign lesions and also to be reliably identified for a more tailored management.

Another systematic review by Patel et al. [24] investigated the success of identifying oncocytomas. Of the 48 lesions that were diagnostic of oncocytoma on RTB, 64.6% was in concordance with analysis following surgical treatment. Meta-analysis determined the PPV of oncocytoma on RTB to be 67% with a notable proportion to be identified as chRCC. Histologically, they are hard to distinguish as both have an eosinophilic cytoplasm. Clinical diagnostic dilemmas between chRCC and oncocytomas still remain. Clinicians should factor this in tailoring an altered AS for oncocytomas.
