Dr Croll on Radiographic Size Change vs irRVT After Neoadjuvant Therapy in RCC

“We [found] that, with this updated pathologic response system, using radiology as a surrogate to predict outcomes is insufficient.”

Benjamin Croll, MD, a urologic oncology fellow at Fox Chase Cancer Center, discussed findings from a study presented during the 2026 American Urological Association (AUA) Annual Meeting evaluating the correlation between radiographic response and pathologic response in renal cell carcinoma (RCC) using immune-related residual viable tumor (irRVT).

Croll highlighted that irRVT provides greater granularity than traditional pathologic reporting by characterizing what occurs at the tumor level as a consequence of treatment, rather than simply quantifying residual disease. Unlike conventional pathologic systems, irRVT captures the immune-mediated changes within the tumor microenvironment, offering a more comprehensive picture of treatment effect, he noted.

Prior studies have established that traditional pathologic reporting does not reliably correlate with radiographic size change, but that this relationship had not been previously examined through the lens of irRVT, Croll explained. In a cohort of 35 patients, the overall correlation between radiographic response and irRVT was poor, he added. Although partial radiographic response was more commonly observed among patients with favorable pathologic outcomes, the association was not consistent across the full cohort, he said.

Croll emphasized the clinical implications of this discordance, noting that 4 patients in the cohort achieved a major pathologic response, yet demonstrated no change on radiographic imaging, he explained. Therefore, relying solely on CT scan–based assessment would have incorrectly suggested treatment failure in these patients, he said.

Radiologic imaging was found to be an insufficient surrogate for pathologic outcomes via irRVT, underscoring the importance of incorporating tissue-based assessments to more accurately capture treatment response and guide subsequent therapeutic decision-making in this patient population, Croll concluded.