Imaging demonstrates that preclinical and human tumors are heterogeneous, i.e. a single tumor can exhibit multiple regions that behave differently during both normal development and also in response to treatment. The large variations observed in control group tumors can obscure detection of significant therapeutic effects due to the ambiguity in attributing causes of change. This can hinder development of effective therapies due to limitations in experimental design, rather than due to therapeutic failure. An improved method to model biological variation and heterogeneity in imaging signals is described. Specifically, Linear Poisson modelling (LPM) evaluates changes in apparent diffusion co-efficient (ADC) before and 72 hours after radiotherapy, in two xenograft models of colorectal cancer. The statistical significance of measured changes are compared to those attainable using a conventional t-test analysis on basic ADC distribution parameters. When LPMs were applied to treated tumors, the LPMs detected highly significant changes. The analyses were significant for all tumors, equating to a gain in power of 4 fold (i.e. equivelent to having a sample size 16 times larger), compared with the conventional approach. In contrast, highly significant changes are only detected at a cohort level using t-tests, restricting their potential use within personalised medicine and increasing the number of animals required during testing. Furthermore, LPM enabled the relative volumes of responding and non-responding tissue to be estimated for each xenograft model. Leave-one-out analysis of the treated xenografts provided quality control and identified potential outliers, raising confidence in LPM data at clinically relevant sample sizes.
翻译:图像显示,临床前肿瘤和人类肿瘤是多种多样的,即单一肿瘤在正常发育期间和在治疗反应期间都表现出不同的行为方式。在控制组肿瘤中观察到的巨大变异会掩盖对重大治疗效应的检测,因为对变化原因的归属模糊不清。这可能会由于实验设计的限制而不是治疗失败而阻碍有效治疗的发展。描述的是模型生物变异和成像信号异性的改进方法。具体地说,线性Poisson模型(LPM)评估了在正常发育期间和放射治疗后72小时的明显共效(ADC)变化,在两种染色癌的Xeograft模型中观察到的显著变化。测量变化的统计意义与使用基本ADC分布参数的常规测试值分析结果的可实现效果相比较。当LPM应用于治疗肿瘤时,LPM检测到了非常显著的变化。对所有肿瘤的分析意义重大,相当于4倍的体积能量(即精度为Xx移植治疗的样本大小,在放射治疗后72小时,在两个色素切癌症的样本中,测测测测测测测得的数值值值值值值值分析中,在每组内测测测测测测测测测得其机值值值值值值值值值值值值值值值值值值中,仅测值中测值中测算的值值值值值值值值值值值值值值值值值值值值值值值值值值值值值值值的值值值值值值值值值值值值的值的值值值值值值值值值值值值值值值值值值值值值值值值值值值值值值值值。