RENAL HISTOPATHOLOGY IN CANCER PATIENTS: RESULTS OF A MULTICENTER STUDY

Abstract Background and Aims Some decades ago, patients with cancer were not submitted to invasive procedures because of their short life expectancy. This is one of the main reasons why data about kidney histology in oncological patients with kidney impairment is very scarce: kidney biopsies were not performed in this population. However, renal biopsy is an especially useful diagnostic and prognostic tool in these patients when they develop kidney injury. The aim of our study is to study clinical and histological characteristics of patients with active solid organ malignancy that underwent kidney biopsy in a multicenter cohort. Method We performed a multicenter collaborative retrospective study. Clinical, demographical, and histological data from patients with an active neoplasia or in active cancer treatment who underwent kidney biopsy were collected. Statistics: Quantitative variables are expressed as mean+/-SD (normal distribution) or median (IQ 25-75) (non-normal distribution).Qualitative variables are expressed as percentage. Actuarial survival curves were performed using Kaplan-Meier. Results 94 patients with cancer who underwent a kidney biopsy during the study period, from 9 hospitals were included.63.8% men, 36.2% woman and mean age 66 (SD +/- 10,95) years old. The indications for biopsy were acute renal failure (63.8%), proteinuria (17%), and exacerbation of chronic kidney disease (11.7%). At the time of the renal biopsy, 27.7% patients presented diabetes, 60.6% high blood pressure, 10.6% were on non-steroidal anti-inflammatory drugs treatment, and 74.5% were receiving renin angiotensin system blockers. Malignances were lung (31.9%), intestinal (13.8%) and prostate (8.5%), with 43.6% metastatic cancer. As oncospecific treatment, 33% received chemotherapy, 30.8% immunotherapy (of which 37.93% received more than 1 checkpoint inhibitor (CPI) and 24.13% had immune-related adverse events), 22.4 % specific therapies, 17 % surgery, and 3.2% conservative treatment. Previously to kidney injury, 51.06% presented Cr> 1 mg / dL. At the time of kidney biopsy, median creatinine was 2,63mg/dL [1,75-3,9 (IQ 25-75)], median urine protein/creatinine ratio 795 mg/g [221-3182(IQ 25-75)]; 51.1% presented haematuria and 22.3% nephrotic range proteinuria; 8.5% eosinophiluria and 7.44% hemolytic anemia and /or low platelet. At the time of renal biopsy, 8.5% presented ANCA and 5.31% decrease in C3 / C4 serum levels. The renal biopsy diagnosis was: 40.4% acute interstitial nephritis, followed by acute tubular necrosis (9.6%), thrombotic microangiopathy (6.4%), membranous nephropathy (5.3%) and IgA nephropathy (6.4%). 62.8% received corticosteroids (28.81% pulses) for an average of 5.8 months [3.7-9.1(IQ 25-75)]. 12.8% required kidney replacement therapy. 43.6% showed complete recovery of kidney function at the end of follow-up. Average follow-up 22.59 months. 40.2% of patients died at the end of follow-up and 72.34 % presented chronic kidney disease. As expected, and maybe related to the heterogeneous cancer disease studied, the only factor associated with mortality was the presence of the metastasis at the moment of kidney biopsy (p=0.028). Conclusion Histological kidney diagnosis in patients with active cancer involves various renal disorders, such as acute interstitial nephritis, thrombotic microangiopathy, membranous nephropathy and IgA nephropathy. Renal biopsy in this group of patients provides valuable diagnostic and prognostic information. More studies are needed to expand the consensus in the diagnosis and treatment of oncological patients with renal injury.