Diagnostic accuracy and inter-reader agreement of the nacVI-RADS for bladder cancer treated with neoadjuvant chemotherapy: a prospective validation study

Objective: The primary aim was to determine the performance of neoadjuvant chemotherapy VI-RADS (nacVI-RADS) in predicting response to systemic therapy in patients with MIBC and to evaluate its inter-reader agreement. Materials and methods: Prospective study, including patients with non-metastatic muscle-invasive bladder cancer (MIBC) who underwent neoadjuvant chemotherapy before radical cystectomy (RC). Patients underwent pre- and post-treatment MRI. Radiological response was evaluated by two experienced radiologists using nacVI-RADS scoring system. Reference standard was defined using histopathological findings. Sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), and accuracy were calculated to assess nacVI-RADS performance for each reader. Inter-reader agreement was determined with Cohen’s k statistics. Results: Fifty-five patients with non-metastatic MIBC, 46 males (84%) and 9 females (16%) with a median age of 69 (interquartile range (IQR) 66–72 years) were enrolled. Diagnostic performance of nacVI-RADS in detecting complete response to neoadjuvant chemotherapy showed a sensitivity of 76.5–85.3% and specificity of 76.2–81%. The area under the curve was 0.93 (95% CI: 0.86–0.99) for detecting any residual tissue, for the more experienced reader. Inter-reader agreement was optimal with a K of 0.85. In the multivariable logistic regression model, the variables showing independent correlation with response prediction to neoadjuvant therapy were nacVI-RADS score (p = 0.01 for the more experienced reader) and tumor regression grade (TRG; p < 0.001). Conclusion: NacVI-RADS scoring system offers a reliable and reproducible approach, employing a well-structured and easily interpretable method, to assess the response to systemic therapy in patients with MIBC. Key Points: Question There is a lack of a standardized approach to distinguish between responders and non-responders to neoadjuvant chemotherapy for muscle-invasive bladder cancer. Findings The neoadjuvant chemotherapy VI-RADS (nacVI-RADS) score diagnostic performance for detecting complete response to neoadjuvant chemotherapy showed 85.3% sensitivity, 81% specificity, and an AUC of 0.93. Clinical relevance NacVI-RADS score represents a valid predictor of response to neoadjuvant systemic therapy, impacting therapeutic decision-making and improving overall patients’ management.