Differences in Renal Tumor Size Measurements for Computed Tomography Versus Magnetic Resonance Imaging: Implications...

To evaluate and compare the accuracy of computed tomography (CT) and magnetic resonance imaging (MRI) in predicting the final pathologic tumor size of partial nephrectomy specimens.

We analyzed a multi-institutional database of 807 patients who underwent robotic partial nephrectomy for a cT1a renal mass from 2006 to 2016. Patients who had a solitary tumor with complete data on the baseline imaging modality and the tumor size (baseline and pathologic) (n = 349) were included for analysis. Baseline tumor size evaluated by both imaging modalities, in addition to the difference between the measurements and final pathologic tumor size (cm) measurements, was compared between patients who received a baseline CT (n = 276, 79.1%) and those who received an MRI (n = 73, 20.9%).

There were no statistically significant differences between any baseline characteristics and receipt of a CT versus MRI. In multivariable analysis adjusting for confounders, there was no significant difference in the baseline tumor size between patients receiving an MRI and those receiving a CT (2.3 versus 2.6 cm; β = -0.13; 95% confidence interval [CI] = -0.33 to 0.07; P = .208). Tumor size on imaging was smaller from final pathology by 0.43 cm on average (P = .002). Measurement error for the measured baseline versus actual pathologic tumor size did not significantly differ for patients receiving an MRI versus those receiving a CT (0.38 versus 0.44 cm; β = -0.06; 95% CI = -0.16 to 0.04; P = .232).

Baseline renal tumor size measurements were not significantly different for CT scan and MRI. Choice of imaging modality can be based on doctor and patient preference, including cost and exposure to radiation.