Value of percent change in tumoral volume measured at T2-weighted and diffusion-weighted MRI to identify responders after neoadjuvant chemoradiation therapy in patients with locally advanced rectal carcinoma

Abstract

Purpose: To evaluate the percent change in tumoral volume measured at T2-weighted magnetic resonance imaging (T2WMRI) and diffusion-weighted (DWI) as a method to identify responders after chemo- and radiation therapy (CRT) in patients with locally advanced rectal carcinoma. Materials and Methods: Forty-five consecutive patients (mean age ± SD: 72 years ± 9.7; male/female = 24/21) with locally advanced rectal carcinoma underwent CRT followed by surgery. Each patient underwent T2WMRI and DWI at 1.5T before and 6 weeks after the completion of CRT. The percent change in tumoral volume before and 6 weeks after CRT was compared in patients classified as responders and nonresponders according to rectal cancer regression grade. Results: Twenty-five patients were classified as responders with either partial (n = 20) or complete response (n = 5), while 20 patients were classified as nonresponders due to stable disease (n = 18) or disease progression (n = 2). Responders vs. nonresponders differed in the percent change of tumoral volume at T2WMRI (−67% ± 26% vs. −29% ± 26%; P < 0.05) and DWI images (−72% ± 24% vs. −33% ± 28%; P < 0.05) with a cutoff ≤ −70% for T2WMRI (sensitivity = 69%, 95% confidence interval [CI]: 48−85%; specificity = 100%, 95% CI 81–100%) and ≤66% for DWI (sensitivity = 73%, 95% CI: 52–88%; specificity = 100%, 95% CI 81–100%). Conclusion: The percent change in tumoral volume at T2WMRI and DWI images can differentiate responders from nonresponders in patients with locally advanced rectal carcinoma after neoadjuvant CRT. J. Magn. Reson. Imaging 2016;44:1415–1424.