[Predictive value of diffusion-weighted magnetic resonance imaging in patients with esophageal carcinoma treated with radiotherapy: an animal trial].

Abstract

Objective: To explore the value of diffusion-weighted magnetic resonance imaging (MR-DWI) technique in predicting the efficacy of radiotherapy in patients with esophageal cancer, using experimental animal models. Methods: BALB/c nude mice were subcutaneously injected with Eca-109 cell lines and then tumor formed. The experimental group (16 cases) received a single dose of 15 Gy (6 MV X-rays) delivered by a medical linear accelerator, while the control group (24 cases) did not receive any treatment. The two groups were scanned every other day, started one day before the radiotherapy. The scanning sequences included T1-weight imaging, T2-weight imaging, and DWI. The observation time was 1 month. According to the changes of the tumor volume and apparent diffusion coefficient (ADC) value of the two groups, 7 key time points were selected to observe the difference of cell density and tissue necrosis ratio between the two groups (6 cases in each group). Results: From day 7 after radiotherapy, the experimental group had statistically smaller volume of transplanted tumors than the control group, namely (1.729±0.906) cm(3) vs (2.671±0.915) cm(3)(P<0.05). From day 3 after radiotherapy, the experimental group had statistically higher ADC values [(1.017±0.255)×10(-6) vs (0.833±0.142)×10(-6) mm(2)/s, P<0.05], lower cell density of transplanted tumor (25.56±1.40 vs 33.48±4.18%, P<0.05), and less proportion of tissue necrosis [(32.19±1.21) % vs (29.16±2.16)%, P<0.05], respectively. The ADC value was negatively correlated with cell density (r=-0.703, P<0.001) and positively correlated with tissue necrosis ratio (r=0.658, P=0.003). Conclusions: Single dose of large fraction radiotherapy could inhibit the growth of xenograft. ADC values may change at the early stage prior to morphological changes of tumor. The change of cell density and necrosis ratio of transplanted tumor are in line with the change of ADC value. MR-DWI has the value of early prediction of esophageal cancer radiotherapy efficacy.