Individualized threshold for tumor segmentation in 18F-FDG PET/CT imaging: the key for response evaluation of neoadjuvant chemoradiation therapy in patients with rectal cancer?

• Autor(a) principal: Theara C.fagundes
• Data de Publicação: 2017
• Outros Autores: Marcelo Mamede, Arnoldo Mafra, Rodrigo g. Silva, Ana c. g. Castro, Luciana c. Silva, Priscilla t. Aguiar, Josiane a. Silva, Eduardo Paulino Júnior, Alexei m. Machado
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UFMG
• Texto Completo: https://doi.org/10.1590/1806-9282.64.02.119; http://hdl.handle.net/1843/55178; https://orcid.org/0000-0001-6157-6511
• topic: Rectal Neoplasms; Neoadjuvant Therapy; 18F-FDG; PET/CT; Neoplasias Retais; Terapia Neoadjuvante; Fluordesoxiglucose F18; Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada

Introduction: The standard treatment for locally advanced rectal cancer (RC) consists of neoadjuvant chemoradiation followed by radical surgery. Regardless the extensive use of SUV max in 18F-FDG PET tumor uptake as representation of tumor glycolytic consumption, there is a trend to apply metabolic volume instead. Thus, the aim of the present study was to evaluate a noninvasive method for tumor segmentation using the 18F-FDG PET imaging in order to predict response to neoadjuvant chemoradiation therapy in patients with rectal cancer. Method: The sample consisted of stage II and III rectal cancer patients undergoing 18F-FDG PET/CT examination before and eight weeks after neoadjuvant therapy. An individualized tumor segmentation methodology was applied to generate tumor volumes (SUV2SD) and compare with standard SUVmax and fixed threshold (SUV40%, SUV50% and SUV60%) pre- and post-therapy. Therapeutic response was assessed in the resected specimens using Dworak’s protocol recommendations. Several variables were generated and compared with the histopathological results. Results: Seventeen (17) patients were included and analyzed. Significant differences were observed between responders (Dworak 3 and 4) and non-responders for SUVmax-2 (p<0.01), SUV2SD-2 (p<0.05), SUV40%-2 (p<0.05), SUV50%-2 (p<0.05) and SUV60%-2 (p<0.05). ROC analyses showed significant areas under the curve (p<0.01) for the proposed methodology with sensitivity and specificity varying from 60% to 83% and 73% to 82%, respectively. Conclusion: The present study confirmed the predictive power of the variables using a noninvasive individualized methodology for tumor segmentation based on 18F-FDG PET/CT imaging for response evaluation in patients with rectal cancer after neoadjuvant chemoradiation therapy.