TY - JOUR
T1 - External Validation of Early Regression Index (ERITCP) as Predictor of Pathologic Complete Response in Rectal Cancer Using Magnetic Resonance-Guided Radiation Therapy
AU - Cusumano, Davide
AU - Boldrini, Luca
AU - Yadav, Poonam
AU - Yu, Gao
AU - Musurunu, Bindu
AU - Chiloiro, Giuditta
AU - Piras, Antonio
AU - Lenkowicz, Jacopo
AU - Placidi, Lorenzo
AU - Broggi, Sara
AU - Romano, Angela
AU - Mori, Martina
AU - Barbaro, Brunella
AU - Azario, Luigi
AU - Gambacorta, Maria Antonietta
AU - De Spirito, Marco
AU - Bassetti, Michael F.
AU - Yang, Yingli
AU - Fiorino, Claudio
AU - Valentini, Vincenzo
N1 - Funding Information:
Disclosures: D.C. and L.B. have received speaker honoraria and travel reimbursement from ViewRay Inc. V.V. has a research agreement with ViewRay Inc. A.R. and L.P. report personal fees from ViewRay Inc. M.M. is supported by an AIRC grant (IG18965).
Publisher Copyright:
© 2020 Elsevier Inc.
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2020/12/1
Y1 - 2020/12/1
N2 - Purpose: Tumor control probability (TCP)-based early regression index (ERITCP) is a radiobiological parameter that showed promising results in predicting pathologic complete response (pCR) on T2-weighted 1.5 T magnetic resonance (MR) images of patients with locally advanced rectal cancer. This study aims to validate the ERITCP in the context of low-tesla MR-guided radiation therapy, using images acquired with different magnetic field strength (0.35 T) and image contrast (T2/T1). Furthermore, the optimal timing for pCR prediction was estimated, calculating the ERI index at different biologically effective dose (BED) levels. Methods and Materials: Fifty-two patients with locally advanced rectal cancer treated with neoadjuvant chemoradiation therapy were enrolled in this multi-institutional retrospective study. For each patient, a 0.35 T T2/T1-weighted MR image was acquired during simulation and on each treatment day. Gross tumor volume was contoured according to International Commission on Radiation Units Report 83 guidelines. According to the original definition, ERITCP was calculated considering the residual tumor volume at BED = 25 Gy. ERI was also calculated in correspondence with several BED levels: 13, 21, 32, 40, 46, 54, 59, and 67. The predictive performance of the different ERI indices were evaluated in terms of receiver operating characteristic curve. The robustness of ERITCP with respect to the interobserver variability was also evaluated considering 2 operators and calculating the intraclass correlation index. Results: Fourteen patients showed pCR. ERITCP correctly 47 of 52 cases (accuracy = 90%), showing good results in terms of sensitivity (86%), specificity (92%), negative predictive value (95%), and positive predictive value (80%). The analysis at different BED levels shows that the best predictive performance is obtained when this parameter is calculated at BED = 25 Gy (area under the curve = 0.93). ERITCP results are robust with respect to interobserver variability (intraclass correlation index = 0.99). Conclusions: This study confirmed the validity and the robustness of ERITCP as a pCR predictor in the context of low-tesla MR-guided radiation therapy and indicate 25 Gy as the best BED level to perform predictions.
AB - Purpose: Tumor control probability (TCP)-based early regression index (ERITCP) is a radiobiological parameter that showed promising results in predicting pathologic complete response (pCR) on T2-weighted 1.5 T magnetic resonance (MR) images of patients with locally advanced rectal cancer. This study aims to validate the ERITCP in the context of low-tesla MR-guided radiation therapy, using images acquired with different magnetic field strength (0.35 T) and image contrast (T2/T1). Furthermore, the optimal timing for pCR prediction was estimated, calculating the ERI index at different biologically effective dose (BED) levels. Methods and Materials: Fifty-two patients with locally advanced rectal cancer treated with neoadjuvant chemoradiation therapy were enrolled in this multi-institutional retrospective study. For each patient, a 0.35 T T2/T1-weighted MR image was acquired during simulation and on each treatment day. Gross tumor volume was contoured according to International Commission on Radiation Units Report 83 guidelines. According to the original definition, ERITCP was calculated considering the residual tumor volume at BED = 25 Gy. ERI was also calculated in correspondence with several BED levels: 13, 21, 32, 40, 46, 54, 59, and 67. The predictive performance of the different ERI indices were evaluated in terms of receiver operating characteristic curve. The robustness of ERITCP with respect to the interobserver variability was also evaluated considering 2 operators and calculating the intraclass correlation index. Results: Fourteen patients showed pCR. ERITCP correctly 47 of 52 cases (accuracy = 90%), showing good results in terms of sensitivity (86%), specificity (92%), negative predictive value (95%), and positive predictive value (80%). The analysis at different BED levels shows that the best predictive performance is obtained when this parameter is calculated at BED = 25 Gy (area under the curve = 0.93). ERITCP results are robust with respect to interobserver variability (intraclass correlation index = 0.99). Conclusions: This study confirmed the validity and the robustness of ERITCP as a pCR predictor in the context of low-tesla MR-guided radiation therapy and indicate 25 Gy as the best BED level to perform predictions.
UR - http://www.scopus.com/inward/record.url?scp=85090309263&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85090309263&partnerID=8YFLogxK
U2 - 10.1016/j.ijrobp.2020.07.2323
DO - 10.1016/j.ijrobp.2020.07.2323
M3 - Article
C2 - 32758641
AN - SCOPUS:85090309263
VL - 108
SP - 1347
EP - 1356
JO - International Journal of Radiation Oncology Biology Physics
JF - International Journal of Radiation Oncology Biology Physics
SN - 0360-3016
IS - 5
ER -