Clinical Cooperation Unit Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120, Heidelberg, Germany.
Department of Radiation Oncology, University Medical Center Mainz, Langenbeckstrasse 1, 55131, Mainz, Germany.
Radiat Oncol. 2020 Jul 11;15(1):171. doi: 10.1186/s13014-020-01613-4.
To date, only limited magnetic resonance imaging (MRI) data are available concerning tumor regression during neoadjuvant radiochemotherapy (RCT) of rectal cancer patients, which is a prerequisite for adaptive radiotherapy (RT) concepts. This exploratory study prospectively evaluated daily fractional MRI during neoadjuvant treatment to analyze the predictive value of MR biomarkers for treatment response.
Locally advanced rectal cancer patients were examined with daily MRI during neoadjuvant RCT. Contouring of the tumor volume was performed for each MRI scan by using T2- and diffusion-weighted-imaging (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.
In total, 171 MRI scans of eight patients were analyzed regarding anatomical and functional dynamics during RCT. Pathological complete response (pCR) could be achieved in four patients, and four patients had a pathological partial response (pPR) following neoadjuvant treatment. T2- and DWI-based volumetry proved to be statistically significant in terms of therapeutic 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 RCT and appeared inadequate to predict treatment response in our patient cohort.
This prospective exploratory study supports the hypothesis that MRI may be able to predict pCR of rectal cancers early during neoadjuvant RCT. Our data therefore provide a useful template to tailor future MR-guided adaptive treatment concepts.
迄今为止，关于直肠癌患者新辅助放化疗期间肿瘤退缩的磁共振成像（MRI）数据有限，这是自适应放疗（RT）概念的前提。本前瞻性研究旨在通过新辅助治疗期间的每日分次 MRI 评估来分析 MR 生物标志物对治疗反应的预测价值。
局部晚期直肠癌患者在新辅助 RCT 期间接受每日 MRI 检查。通过 T2 加权和弥散加权成像（DWI）序列对每个 MRI 扫描进行肿瘤体积轮廓勾画。计算每日表观弥散系数（ADC）。分析 RCT 期间肿瘤的容积和功能变化，并与手术切除后的病理反应相关联。
共分析了 8 例患者的 171 次 MRI 扫描，以评估 RCT 期间的解剖和功能动态。4 例患者达到病理完全缓解（pCR），4 例患者新辅助治疗后出现病理部分缓解（pPR）。基于 T2 和 DWI 的体积测量在治疗反应方面具有统计学意义，并且在 RCT 的第二周和第四周定义了体积阈值，以预测 pCR。相比之下，在 RCT 期间，两组的平均肿瘤 ADC 值广泛重叠，在我们的患者队列中，似乎不足以预测治疗反应。
这项前瞻性探索性研究支持 MRI 可能能够在新辅助 RCT 早期预测直肠癌 pCR 的假说。因此，我们的数据为定制未来基于 MR 的自适应治疗概念提供了有用的模板。
