Feasibility of using CT volume as a predictor of specimen weight in a subgroup of patients with low risk Wilms tumors registered on COG Study AREN03B2: Implications for central venous catheter placement

ObjectivePatients with stage I Wilms tumor, age ≤2 years, tumor ≤550 g may not require therapy beyond nephrectomy. This study's aims were to determine: (1) if a linear relationship exists between tumor weight and computed tomography (CT) estimated volume; (2) describe the accuracy of a slope–intercept equation in estimating weight; and (3) determine the potential impact of weight estimation on port placement decisions.Materials and methodsTumor weight and port placement information were abstracted from 105 patients, age ≤2 years, with tumors ±550 g, enrolled in COG AREN03B2. One radiologist estimated tumor size from CT scan. Prolate ellipse volume (PEV) was calculated, linear regression performed, slope–intercept equation calculated, equation estimated weight determined, and potential impact of the on port placement evaluated.ResultsA strong relationship exists between PEV and weight (R2 = 0.87). The slope–intercept equation for weight was: weight = 1.04(PEV) + 58.75. Overall median relative error for the equation was 0.9%, and −3% in tumors weighing 350–750 g. Fifty-five ports were placed, 29 in patients with tumor weight ≤550 g, and six not placed in patients with tumor weight >550 g.ConclusionsThe relationship between PEV and weight produced a reliable weight prediction equation. Preoperative consideration of specimen weight may diminish the number of ports placed in this population.