#6294 UTILITY OF KIDNEY BIOPSY AND SPECTRUM OF BIOPSY PROVEN KIDNEY DISEASES IN PATIENTS WITH MALIGNANCY: A RETROSPECTIVE SINGLE-CENTER EXPERIENCE
Authors: Tan Hui Zhuan , Ho Pin Hui , Loh Alwin Hwai Liang , Mok Irene , Lim Cynthia , Ahmed Syed Salahuddin , Chng Tze Wei , Chin Yok Mooi , Teng Esther Wl , Choo Jason 
Published: June 2023

Abstract

Background and Aims
Kidney biopsy may improve diagnostic accuracy and aid in the management of cancer patients with kidney diseases. However, literature on the utility of kidney biopsy in cancer patients and survivors is lacking. We aimed to evaluate the clinical characteristics of cancer patients who underwent kidney biopsy, as well as the histological spectrum of biopsy proven kidney diseases in this cohort.

Method
This was a single-center retrospective study of all patients who had native kidney biopsies at the Singapore General Hospital between 1st October 2015 to 31st December 2022. Demographic, clinical, laboratory and histological data were retrieved from electronic medical records to identify patients with solid-organ or hematological malignancies who underwent kidney biopsy.

Results
Out of 1208 patients who underwent kidney biopsy between 1st October 2015 to 31st December 2022, 116 (9.6%) patients had diagnoses of solid-organ or hematological malignancies. Approximately two-thirds (79/116; 68.1%) had solid-organ malignancies, of which 21.5% had metastatic disease at time of biopsy. Approximately one-third (36/116; 31.0%) had hematological malignancies, of which 10 (8.6%) had a hematological stem-cell transplant (HSCT). One (0.9%) patient had both solid-organ and hematological malignancies. Sixty-eight (58.6%) patients were in remission at time of biopsy, comprising of 52 (44.8%) and 16 (13.8%) patients with solid -organ and hematological malignancies, respectively. Median age at biopsy was 65.7 years (IQR 56.5, 71.4) and majority was female (61/116; 52.6%). Comorbidities of hypertension, type 2 diabetes mellitus, autoimmunity, and liver transplant were found in 36.2% (42/116), 23.3% (27/116), 8.6% (10/116) and 1.7% (2/116) patients respectively. Median serum creatinine at time of biopsy was 152.0μmol/L (IQR 101.8, 220.5). Micro-hematuria was present in approximately two-thirds (68.1%) of patients. Nephrotic range proteinuria and nephrotic syndrome were observed in one-quarter (25.9%) and one-third (31.0%) of the patients, respectively. Approximately half (49.1%) of the patients had acute kidney injury at time of biopsy, while one-fifth (19.8%) had progressive chronic kidney disease. A wide spectrum of histological diagnoses was observed. Glomerulonephritides, tubulointerstitial inflammation and/or glomerular endothelial injuries were diagnosed in 60.8% (48/79) of solid-organ and 80.6% (29/37) of hematological malignancies. Amongst patients with active solid-organ malignancies (n = 20), acute tubulointerstitial nephritis (ATIN) (5/20, 25.0%), IgA nephropathy (3/20; 15.0%) and lupus nephritis (3/20; 15.0%) were the most common primary diagnoses. Amongst patients with active hematological malignancies (n = 17), dysproteinemic kidney disease and/or leukemic infiltration was most frequently diagnosed (6/17; 35.9%). Compared to remission status, active malignancy was not associated with an increased likelihood of an overall diagnosis of glomerulonephritides, tubulointerstitial inflammation and/or glomerular endothelial injuries (p = 0.16). Specifically, the incidence of membranous nephropathy was similar in patients with active malignancy and those in remission (p = 0.42). Amongst patients with HSCT, thrombotic microangiopathy (40.0%) was observed most frequently. Overall, onco-therapeutics-related kidney injuries were present in 13 (11.2%) patients, of which ATIN (38.4%) was most commonly encountered, followed by glomerular endothelial injury (30.7%).

Conclusion
Kidney biopsy provides valuable diagnostic information amongst cancer patients. While a broad spectrum of histological diagnoses can be observed, glomerular diseases and onco-therapeutics-related kidney injuries remain the most common.