562 Biopsy of Localised Renal Masses Offers High Diagnostic Yield and Low Complication Rate in Patients with Suspicious Renal Masses

Aim Biopsy of localised renal masses is generally accurate at detecting benign or malignant histology but can cause complications. The aim of this study was to determine the detection rate and complication rate of renal mass biopsies. Method Patients undergoing a renal mass biopsy at a single tertiary centre between January 2015 and December 2019 were identified electronically using a prospective database. Details about their biopsies were recorded including tumour size, radiological guidance, number of cores, longest margin of biopsy, accuracy of biopsy, histology type, and complications. Results This study included 334 biopsies (Median age 68 years (IQR 60-72); 61.4% (n = 204) male). Median size of tumour was 30mm (IQR 25-50) and 79.9% (n = 267) were solid masses. The biopsies were done under ultrasound (78.4%) or computed tomography (21.6%) guidance. 91.9% had core biopsies (n = 307) with median biopsy margin of 14mm (IQR 9-21). Benign histology was observed in 18.9% (n = 63), malignant in 72.1% (n = 241) while biopsy was non-diagnostic in 9.0% (n = 30). 62.6% (n = 209) of the cases were renal cell carcinoma with clear cell subtype more commonly seen (72.2%, n = 151). Complications following biopsy included haematoma (n = 7, 2.1%), haemorrhage (n = 3, 0.9%), pneumothorax (n = 1, 0.3%) and vasovagal episode (n = 1, 0.3%), resulting in an overall complication rate of 3.6%. Conclusions Biopsy of localised renal masses in this study showed a detection rate of 91% and complication rate of 3.6%. This study suggests renal mass biopsies have high diagnostic yield and low complication rate.

66 Significance of Percutaneous Biopsy in the Clinical Management of Renal Masses

Aim Percutaneous renal mass biopsy is increasingly used in the management of renal masses. The objective of our study was to determine the significance of percutaneous renal mass biopsy and its impact on clinical management. Method Retrospective study of all patients who had image guided percutaneous renal mass biopsy health-board wide from April 2011 to April 2019. Renal mass biopsies were performed for either a localised or metastatic renal mass. Results of the renal biopsies were compared to final diagnosis to determine diagnostic accuracy measured by sensitivity, specificity, negative predictive value and positive predictive value. Results Out of 429 patients who had a renal biopsy, 91 patients- 55 males (61%) and 36 females (39%) were included in the final analysis. The mean age of the study population was 66 years (range 46-87). Renal mass biopsies were performed using coaxial 18-gauge core needle technique. We categorised patients into two groups (metastatic renal masses and localised renal mass). Sixty-eight patients had biopsies for metastatic disease and 23 patients had biopsies for a localised renal mass. In the localised disease group, the sensitivity was 100%, positive predictive value was 82% (95% CI, 48.2-97.7%) and the negative predictive value was 100% (95% CI, 66.4-100%) (Clopper Pearson Method). For patients with metastatic renal mass the positive predictive value was 83%. Conclusions Percutaneous renal mass biopsy may have a role for metastatic renal cancers that require targeted therapy and localised masses that require curative treatment.

Optimizing the management of patients with small renal masses in a Canadian context: A Markov decision-analysis model

Introduction: The management of patients with a small renal mass (SRM) varies significantly. The objective of this study was to determine which initial management strategy resulted in the greatest quality-adjusted life months (QALM) for an index patient with a SRM. Methods: A Markov decision analysis was used to determine the effect of 1) treating patients with a partial nephrectomy (PN); 2) active surveillance; and 3) renal mass biopsy on QALM over a 10-year horizon. All relevant health states were modelled. Biopsy sensitivity and specificity were modelled assuming an 80% prevalence of cancer using procedural pathology as the gold standard. Health state utilities were obtained from the Tufts Medical Centre Cost-Effective Analysis Registry. Deterministic sensitivity analyses were used to test key assumptions. Results: Over a 10-year time horizon for a 70-year-old male with a 2 cm SRM, the biopsy strategy resulted in 38.07 QALM, whereas treating all patients with PN resulted in 37.69 QALM and active surveillance in 36.25 QALM. The model was most sensitive to the probability that a patient would remain alive at baseline. Biopsy was the preferred strategy when sensitivity was greater than 77%. As the underlying probability of cancer increased, the threshold of renal mass biopsy sensitivity to still favor biopsy increased. Conclusions: Renal mass biopsy is the preferred initial management strategy for an index patient with a SRM to optimize QALM. When the probability of cancer is high, centers should aim for a sensitivity of at least 77% in order to consider a biopsy first strategy.