Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University, Baltimore, MD 21231-2410, USA.
Semin Radiat Oncol. 2012 Jul;22(3):220-32. doi: 10.1016/j.semradonc.2012.03.007.
Predicting radiotherapy (RT) treatment response and eventual locoregional disease control is an important component of the ongoing effort to improve the therapeutic ratio in the management of head and neck squamous cell carcinomas. The development of clinically useful predictive and prognostic imaging biomarkers has been limited by significant tumor heterogeneity in both the tumor and its microenvironment. Various advanced imaging techniques have been evaluated in the head and neck squamous cell carcinoma patient, which now offer a strategy to identify and quantify this heterogeneity, characterizing the tumor at baseline and its response to RT. The most promising of these techniques include dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), DCE computed tomography, diffusion-weighted MRI, and (18)F-fluoromisonidazole positron emission tomography (PET) all relying on the spatiotemporal quantification of a contrast agent within a region of interest that can be further analyzed by various pharmacokinetic models. Despite the small study populations, several consistent observations have been reported that warrant further validation. Features associated with a favorable RT response include tumors with an effective vasculature characterized by rapid and high influx rates of the contrast agent and its effective clearance with little or no regions of hypoxia. (18)F-deoxyglucose-PET imaging remains an active area of investigation with the metabolic tumor volume parameter appearing to offer potential predictive value. Characterizing changes during a course of RT may offer greater predictive value. Both DCE-MRI and diffusion-weighted MRI can identify physiological changes within the first 1-2 weeks of treatment that are correlated with long-term clinical outcome. Identifying persistent hypoxia with (18)F-fluoromisonidazole-PET during a course of RT suggests an increased risk of relapse. Whether this is due to an inability to favorably remodel the tumor's vasculature has not been clearly demonstrated to date. Future research goals include the need to further validate these promising imaging biomarkers especially in larger cohorts of patients, characterizing the optimal threshold cutoffs and to refine the predictive value by incorporating the assessments of early tumor responses to therapy that offer the potential for increased specificity because it reflects the biological stress responses.
预测放疗 (RT) 治疗反应和最终局部区域疾病控制是提高头颈部鳞状细胞癌治疗效果的重要组成部分。由于肿瘤及其微环境中存在显著的肿瘤异质性，临床上有用的预测和预后成像生物标志物的发展受到限制。各种先进的成像技术已经在头颈部鳞状细胞癌患者中进行了评估，这些技术现在提供了一种策略，可以识别和量化这种异质性，对头颈部鳞状细胞癌患者的肿瘤进行基线特征描述，并对其对 RT 的反应进行特征描述。这些技术中最有前途的包括动态对比增强磁共振成像 (DCE-MRI)、DCE 计算机断层扫描、扩散加权磁共振成像和 (18)F-氟代米索硝唑正电子发射断层扫描 (PET)，这些技术都依赖于对感兴趣区域内的造影剂进行时空定量，这些造影剂可以通过各种药代动力学模型进一步分析。尽管研究人群较小，但已经报告了一些一致的观察结果，这些结果需要进一步验证。与 RT 反应良好相关的特征包括具有快速和高流入率的有效血管生成的肿瘤，以及造影剂及其有效清除的特征，很少或没有缺氧区域。(18)F-脱氧葡萄糖-PET 成像仍然是一个活跃的研究领域，代谢肿瘤体积参数似乎具有潜在的预测价值。在 RT 过程中描述变化可能具有更大的预测价值。DCE-MRI 和扩散加权 MRI 都可以在治疗的前 1-2 周内识别出与长期临床结果相关的生理变化。在 RT 过程中用 (18)F-氟代米索硝唑-PET 识别持续缺氧表明复发风险增加。这是否是由于肿瘤血管无法有利地重塑还没有得到明确证明。未来的研究目标包括需要进一步验证这些有前途的成像生物标志物，特别是在更大的患者队列中，描述最佳阈值截止值，并通过纳入对早期肿瘤对治疗的反应评估来提高预测价值，这可能提高特异性，因为它反映了生物学应激反应。
