Online

ESTRO 2020

Session Item

Clinical track: Lower GI (colon, rectum, anus)
9306
Poster
Clinical
23:00 - 23:00
Response prediction by daily fractional MRI during neoadjuvant radiochemotherapy in rectal cancer
PO-1099

Abstract

Response prediction by daily fractional MRI during neoadjuvant radiochemotherapy in rectal cancer
Authors: Bostel|, Tilman(1,2)*[tilman.b@gmx.net];Dreher|, Constantin(3,4);Wollschläger|, Daniel(5);Mayer|, Arnulf(1);Bickelhaupt|, Sebastian(6);Schlemmer|, Heinz-Peter(4);Huber|, Peter(2,7);Sterzing|, Florian(8);Debus|, Jürgen(2,7);Nicolay|, Nils(2,9);
(1)University Medical Center Mainz, Radiation Oncology, Mainz, Germany;(2)German Cancer Research Center DKFZ, Clinical Cooperation Unit Radiation Oncology, Heidelberg, Germany;(3)Mannheim University Hospital, Radiation Oncology, Mannheim, Germany;(4)German Cancer Research Center DKFZ, Division of Radiology, Heidelberg, Germany;(5)University Medical Center Mainz, Institute of Medical Biostatistics- Epidemiology and Informatics IMBEI, Mainz, Germany;(6)German Cancer Research Center DKFZ, Division of Medical Imaging and Radiology – Cancer Prevention, Heidelberg, Germany;(7)Heidelberg University Hospital, Radiation Oncology, Heidelberg, Germany;(8)Kempten Clinic, Radiation Oncology, Kempten, Germany;(9)Medical Center - University of Freiburg, Radiation Oncology-, Freiburg, Germany;
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Purpose or Objective

Only few data are available on MR imaging during neoadjuvant treatment of rectal carcinomas, that may help to devise adaptive radiotherapy (RT) concepts. This study aimed at prospectively evaluating daily fractional MRI during neoadjuvant radiochemotherapy (RCT) to analyze the predictive value of MR biomarkers for treatment response.

Material and Methods

Locally advanced rectal cancer patients were examined with daily MRI during neoadjuvant RCT. Tumor delineation was performed on each MRI scan based on T2 and DWI sequences. The daily apparent-diffusion coefficient (ADC) was calculated. Volumetric and functional tumor changes during RCT were analyzed and correlated with the pathological response after surgical resection.

Results

A total of 171 MRI scans in eight patients were performed with regard to morphological and functional changes of the tumor tissue during RCT. In four patients, there was a complete pathological remission (pCR), while the other four patients achieved a partial remission (pPR) after neoadjuvant RCT and surgical resection. Volumetry based on T2- and diffusion-weighted imaging was statistically significant in terms of treatment response, and volumetric thresholds at week two and week four during RCT were defined for the prediction of pCR. In contrast, the average tumor ADC values widely overlapped between both response groups during neoadjuvant RCT and appeared inadequate to predict treatment response in this cohort.

Conclusion

This prospective study supports the hypothesis that some MR biomarkers can predict a pCR of rectal cancer during neoadjuvant RCT. Our data provide a useful template to tailor future MR-guided adaptive treatment concepts.