磁共振扩散加权成像表观扩散系数值与局部进展期胃癌新辅助化疗预后的关系

Correlation of diffusion weighted MR imaging with the prognosis of local advanced gastric carcinoma after neoadjuvant chemotherapy

目的：探讨局部进展期胃癌新辅助化疗后磁共振扩散加权成像（DWI）表观扩散系数值（ADC值）的变化及其与长期预后的关系。方法前瞻性纳入2010年11月至2011年9月在北京大学肿瘤医院行新辅助化疗的24例局部进展期胃癌患者，分别于新辅助化疗前后行磁共振检查。 T2加权序列测量癌肿胃壁厚度，DWI序列测量胃癌ADC值，分别以边缘勾勒和类圆形感兴趣区获得反映病灶整体的ADCentire值和高活性区域的ADCmin值。根据3年生存情况将全部病例分为长期生存组（14例）和预后不良组（10例），比较两组间定量参数基线值及治疗后变化率的差异，评估上述定量参数预测长期生存的效能。结果长期生存组和预后不良组治疗前ADCmin值[（1．17±0．23）×10－3 mm2／s比（1．23±0．27）×10－3 mm2／s]及ADCentire值[（1．43±0．20）×10－3 mm2／s比（1．50±0．24）×10－3 mm2／s]的差异均无统计学意义（均P＞0．05）。新辅助化疗后，长期生存组较预后不良组ADCmin值升高率（中位数：21％比5％）及ADCentire值升高率（中位数：23％比1％）增高（P＝0．06，P＝0．02）。治疗前肿瘤厚度、ADCmin值及ADCentire值评估长期生存的曲线下面积分别为0．693、0．543和0．600；治疗后厚度值、ADCmin值及 ADCentire值变化率预测长期生存的曲线下面积分别为0．532、0．729和0．779。取ADC值升高率大于或等于15％预测长期生存，ADCmin值的阳性预测值为81．8％（9／11）， ADCentire值的阳性预测值为83．3％（10／12）；取ADC值升高率小于或等于10％预测预后不良，ADCmin值的阳性预测值为63．6％（7／11），ADCentire值的阳性预测值为70．0％（7／10）。结论胃癌新辅助化疗后ADC值的变化率与患者预后存在相关性，ADC值升高明显的患者长期生存比例较高；反映肿瘤整体特性的ADCentire值预测效能优于反映肿瘤高活性部分的ADCmin值。

Objective To investigate the correlation of the apparent diffusion coefficient （ADC） on diffusion-weighted MRI （DWI） with the prognosis of locally advanced gastric carcinoma after neoadjuvant chemotherapy （NACT）. Methods Patients with locally advanced gastric carcinoma undergoing NACT in our hospital from November 2010 to September 2011 were enrolled in this prospective study. MRI examinations were performed before and after NACT. ADCs of the whole lesion （ADCentire） and high signal area on DWI （ADCmin） were calculated, and the cancer thickness on T2-weighted images was measured. All the patients were divided into long-term survival group and poor prognosis group, according to the 3-year survival status. The pre-therapy baseline values and early percentage changes （%△） of the above parameters were compared between the two groups. Receiver operating characteristics （ROC） curves were employed to compare the performance of the above parameters in the discrimination of different prognosis groups. Results A total of 24 patients were enrolled in the study. There were 14 patients of long-term survival group and 10 patients of poor prognosis group. No statistical difference in baseline ADCmin and ADCentire was shown between long-term survival group and poor prognosis group [ADCmin： （1.17±0.23）×10-3 mm2/s vs. （1.23±0.27） ×10-3 mm2/s, P〉0.05; ADCentire： （1.43±0.20）×10-3 mm2/s vs. （1.50±0.24）×10-3 mm2/s, P〉0.05]. The %△ADCmin and %△ADCentire were both higher in long-term survival group than those in poor prognosis group （%△ADCmin： 21% vs. 5%, P=0.06; %△ADCentire： 23% vs. 1%, P=0.02）. Through ROC curves, the AUCs for pre-therapy cancer thickness, ADCmin and ADCentire were 0.693, 0.543 and 0.600 respectively, and AUCs for %△thickness, %△ADCmin and %△ADCentire were 0.532, 0.729 and 0.779 respectively, in the differentiation of prognosis. Using %△ADC≥15% to predict long-term survival, the positive predictive value （PPV） for %△ADCmin was 81.8% and %△ADCentire was 83.3%. Using %△ADC≤10% to predict poor prognosis, the PPV for %△ADCmin was 63.6% and%△ADCentire was 70.0%. Conclusions The change of ADC after NACT of gastric carcinoma is correlated with long-term prognosis. The significantly increased ADC is prone to signify long-term survival. ADCentire is better than ADCmin in the prognosis prediction.