Mahmood Faisal, Johannesen Helle H, Geertsen Poul, Hansen Rasmus H
Radiotherapy Research Unit (RRU), Department of Oncology, University of Copenhagen, Herlev and Gentofte Hospital, Herlev, Denmark.
Phys Med Biol. 2017 Apr 21;62(8):2990-3002. doi: 10.1088/1361-6560/aa5249. Epub 2017 Mar 17.
An imaging biomarker for early prediction of treatment response potentially provides a non-invasive tool for better prognostics and individualized management of the disease. Radiotherapy (RT) response is generally related to changes in gross tumor volume manifesting months later. In this prospective study we investigated the apparent diffusion coefficient (ADC), perfusion fraction and pseudo diffusion coefficient derived from diffusion weighted MRI as potential early biomarkers for radiotherapy response of brain metastases. It was a particular aim to assess the optimal time point for acquiring the DW-MRI scan during the course of treatment, since to our knowledge this important question has not been addressed directly in previous studies. Twenty-nine metastases (N = 29) from twenty-one patients, treated with whole-brain fractionated external beam RT were analyzed. Patients were scanned with a 1 T MRI system to acquire DW-, T2W-, T2W- and T1W scans, before start of RT, at each fraction and at follow up two to three months after RT. The DW-MRI parameters were derived using regions of interest based on high b-value images (b = 800 s mm). Both volumetric and RECIST criteria were applied for response evaluation. It was found that in non-responding metastases the mean ADC decreased and in responding metastases it increased. The volume based response proved to be far more consistently predictable by the ADC change found at fraction number 7 and later, compared to the linear response (RECIST). The perfusion fraction and pseudo diffusion coefficient did not show sufficient prognostic value with either response assessment criteria. In conclusion this study shows that the ADC derived using high b-values may be a reliable biomarker for early assessment of radiotherapy response for brain metastases patients. The earliest response stratification can be achieved using two DW-MRI scans, one pre-treatment and one at treatment day 7-9 (equivalent to 21 Gy).
一种用于早期预测治疗反应的成像生物标志物可能为疾病的更好预后和个体化管理提供一种非侵入性工具。放射治疗（RT）反应通常与数月后出现的肿瘤总体积变化有关。在这项前瞻性研究中，我们研究了扩散加权MRI得出的表观扩散系数（ADC）、灌注分数和伪扩散系数，作为脑转移瘤放射治疗反应的潜在早期生物标志物。特别目的是评估在治疗过程中获取DW-MRI扫描的最佳时间点，因为据我们所知，这个重要问题在以前的研究中尚未直接解决。分析了21例接受全脑分割外照射放疗的患者的29个转移瘤（N = 29）。在放疗开始前、每个分次放疗时以及放疗后两到三个月的随访期间，使用1T MRI系统对患者进行扫描，以获取DW、T2W、T2W和T1W扫描。基于高b值图像（b = 800 s/mm²）使用感兴趣区域得出DW-MRI参数。体积标准和RECIST标准均用于反应评估。结果发现，在无反应的转移瘤中，平均ADC降低，而在有反应的转移瘤中，平均ADC升高。与线性反应（RECIST）相比，基于体积的反应通过第7次及以后分次放疗时发现的ADC变化更一致地被预测。灌注分数和伪扩散系数在任何一种反应评估标准下均未显示出足够的预后价值。总之，本研究表明，使用高b值得出的ADC可能是脑转移瘤患者放射治疗反应早期评估的可靠生物标志物。最早的反应分层可以通过两次DW-MRI扫描实现，一次在治疗前，一次在治疗第7 - 9天（相当于21 Gy）。
