Accurate Prediction of Pathological Rectal Tumor Response after Two Weeks of Preoperative Radiochemotherapy Using {sup 18}F-Fluorodeoxyglucose-Positron Emission Tomography-Computed Tomography Imaging

Journal Article · Tue Jun 01 00:00:00 EDT 2010 · International Journal of Radiation Oncology, Biology and Physics

DOI:https://doi.org/10.1016/j.ijrobp.2009.04.030· OSTI ID:21372285

Ollers, Michel C ^[1]; Riedl, Robert G ^[2]; Buijsen, Jeroen; Lambin, Philippe; Lammering, Guido ^[1]

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1. Department of Radiation Oncology (MAASTRO), GROW Research Institute, University Medical Centre Maastricht, Maastricht (Netherlands)
2. Department of Pathology, University Medical Centre Maastricht, Maastricht (Netherlands)

Purpose: To determine the optimal time point for repeated {sup 18}F-fluorodeoxyglucose-positron emission tomography (PET)-CT imaging during preoperative radiochemotherapy (RCT) and the best predictive factor for the prediction of pathological treatment response in patients with locally advanced rectal cancer. Methods and Materials: A total of 30 patients referred for preoperative RCT treatment were included in this prospective study. All patients underwent sequential PET-CT imaging at four time points: prior to therapy, at day 8 and 15 during RCT, and shortly before surgery. Tumor metabolic treatment responses were correlated with the pathological responses by evaluation of the tumor regression grade (TRG) and the pathological TN (ypT) stage of the resected specimen. Results: Based on their TRG evaluations, 13 patients were classified as pathological responders, whereas 17 patients were classified as pathological nonresponders. The response index (RI) for the maximum standardized uptake value (SUV{sub max}) on day 15 of RCT was found to be the best predictive factor for the pathological response (area under the curve [AUC] = 0.87) compared to the RI on day 8 (AUC = 0.78) or the RI of presurgical PET imaging (AUC = 0.66). A cutoff value of 43% for the reduction of SUV{sub max} resulted in a sensitivity of 77% and a specificity of 93%. Conclusions: The SUV{sub max}-based RI calculated after the first 2 weeks of RCT provided the best predictor of pathological treatment response, reaching AUCs of 0.87 and 0.84 for the TRG and the ypT stage, respectively. However, a few patients presented with peritumoral inflammatory reactions, which led to mispredictions. Exclusion of these patients further enhanced the predictive accuracy of PET imaging to AUCs of 0.97 and 0.89 for TRG and ypT, respectively.

• OSTI ID: 21372285
• Journal Information: International Journal of Radiation Oncology, Biology and Physics, Vol. 77, Issue 2; Other Information: DOI: 10.1016/j.ijrobp.2009.04.030; PII: S0360-3016(09)00598-7; Copyright (c) 2010 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0360-3016
• Country of Publication: United States
• Language: English

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