Incremental value of MRI for preoperative penile cancer staging

Purpose: To evaluate the incremental value of magnetic resonance imaging (MRI), compared to clinical examination, for penile cancer (PC) local staging. Materials and Methods: Twenty-five consecutive patients with histologically proven PC were evaluated prospectively. MRI staging was performed on 1.5 and 3.0T scanners using high-resolution T₂-weighted and postcontrast T₁-weighted images. Two blinded observers interpreted MR images. Clinical local staging was performed by experienced urologists. The pathology report was used as the standard of reference. Results: The interobserver agreement for MRI staging, using a kappa test for T-staging was moderate, 0.52 (95% confidence interval [CI] = 0.24–0.78), P = 0.001, although a high correlation for N-staging, 0.72 (95% CI = 0.42–1.00), P = 0.001, was detected. Clinical staging was correct in 52.0% (13/25) of patients. After pathological staging, five (20.0%) lesions were upstaged and seven (28.0%) lesions were downstaged compared to clinical examination. MRI accurately defined T-staging in 18/25 lesions (72.0%). After pathologic staging, five (20.0%) were upstaged and two downstaged (8.0%), compared to MRI. Fifteen patients were submitted to inguinal and pelvic lymphadenectomy and considered for comparison of accuracy of nodal staging by physical examination and MRI. Clinical staging accurately staged 7/15 patients (46.7%). After histopathologic analysis, six cases had nodal staging upgraded and two cases were downgraded. MRI correctly staged 13/15 (86.7%). Using a chi-square for comparison, differences in proportion of corrected staging between clinical examination and MRI were not significant for T-staging (P = 0.14), but were significant for nodal staging (P = 0.02). Conclusion: According to our results, MRI improves local staging of PC patients, particularly for those with limited physical examination. Level of Evidence: 1. J. Magn. Reson. Imaging 2017;45:118–124.