IMPORTANCE
Early detection of small asymptomatic kidney tumors presages better patient outcome. Incidental discovery of asymptomatic renal tumors by abdominal imaging is expensive and cannot reliably distinguish benign from malignant tumors.
OBJECTIVE
This investigation evaluated the clinical utility, sensitivity and specificity of urine aquaporin-1 (AQP1) and perilipin-2 (PLIN2) concentrations as unique noninvasive biomarkers to diagnose malignant clear cell or papillary renal cell carcinoma (RCC) in a screening paradigm.
DESIGN, SETTING, AND PARTICIPANTS
Urine samples were obtained from 720 patients undergoing routine abdominal CT (screening population), 80 healthy controls and 19 patients with pathologically confirmed RCC. Urine AQP1 and PLIN2 concentrations were measured by sensitive and specific ELISA and Western blot procedures, respectively.
MAIN OUTCOMES AND MEASURES
AQP1 and PLIN2 were measured prospectively in a screening paradigm in an otherwise asymptomatic population. The absence or presence of a renal mass and of RCC, were verified by abdominal computed tomography (CT) and by post-nephrectomy pathologic diagnosis, respectively.
RESULTS
Median urine AQP1 and PLIN2 concentrations in patients with known RCC were more than 12-fold higher (P<0.0001 each) than controls and the screening population. The area under the receiver operating characteristic curve for urine AQP1 and PLIN2 concentrations individually or in combination was ≥0.92, with ≥85% sensitivity and ≥87% specificity compared with control or screening patients. Three of the 720 screening patients had biomarker concentrations suggestive of RCC and were found to have an imaged renal mass by CT. Two patients, evaluated further, had RCC.
CONCLUSIONS AND RELEVANCE
These results demonstrate the clinical utility, specificity and sensitivity of urine AQP1 and PLIN2 to diagnose RCC. These novel tumor-specific proteins have high clinical validity and substantial potential as specific diagnostic and screening biomarkers for clear cell and papillary RCC, and in the differential diagnosis of imaged renal masses.