胃癌调强放疗后胰腺亚临床功能损伤评估与保护

Evaluation of pancreatic subclinical dysfunction and sparing of pancreas after intensity-modulated radiation therapy for gastric cancer

目的通过相关生化指标和胰腺体积改变来评估胃癌调强放疗(IMRT)后胰腺亚临床功能损伤,并探讨通过剂量学预测以及剂量限制来降低胰腺剂量。方法回顾性选择接受45 Gy术后辅助放化疗且无胰腺基础疾病的胃癌患者30例,勾画胰腺并评估剂量及与计划靶体积(PTV)解剖位置关系。分析放疗前后患者空腹血糖、血清脂肪酶和血清淀粉酶以及胰腺体积值变化。应用Pearson分析上述生化指标和体积值变化与胰腺剂量相关性,应用受试者工作特征(ROC)曲线分析相关剂量学预测阈值。探讨IMRT中剂量限制可行性。结果30例患者胰腺体积为37.6 cm^(3),其中89%包在PTV内。胰腺D_(mean)为45.92 Gy,其中胰头、胰体、胰尾D_(mean)分别为46.45、46.46、45.80 Gy。患者空腹血糖值变化不明显。放疗后6、12个月血清脂肪酶分别较放疗前下降66%、77%(P<0.001),血清淀粉酶分别下降24%、38%(P<0.001)。22例胰腺体积在放疗后18个月内下降了47%。ROC曲线分析得出胰腺V_(45Gy)对放疗后6个月脂肪酶、淀粉酶以及12个月淀粉酶下降1/3具有最佳预测价值,切点值为V_(45Gy)<85%;胰腺D_(mean)对放疗后12个月血清脂肪酶下降2/3具有最佳预测价值,切点值为D_(mean)<45.01 Gy。按"整个胰腺"和"PTV外胰腺"限量后胰腺V_(45Gy)分别下降11%和7%、胰腺D_(mean)分别下降2%和2%、胰尾D_(mean)各下降3%。结论血清脂肪酶和血清淀粉酶在胃癌术后辅助放疗后6、12个月出现明显下降,胰腺体积在放疗后18个月内出现了明显缩小。胰腺V_(45Gy)<85%和D_(mean)<45.01 Gy是血清脂肪酶和淀粉酶下降的剂量预测值,相应剂量学限制可以一定程度降低其剂量。

Objective To evaluate the pancreatic subclinical dysfunction after intensity-modulated radiation therapy(IMRT)for gastric cancer by analyzing biochemical indexes and pancreatic volume changes,and to reduce the dose of pancreas by dosimetric prediction and dose limitation.Methods 30 patients with gastric cancer who received 45Gy postoperative adjuvant radiotherapy were retrospectively selected.The pancreas was delineated and its dose and anatomical relationship with planning target volume(PTV)were evaluated.Fasting blood glucose,serum lipase and amylase,and pancreatic volume changes before and after radiotherapy were analyzed.The correlation between the changes of biochemical indexes and volume and pancreatic dose was evaluated by Pearson analysis.The threshold of the dosimetric prediction was obtained by receiver operating characteristic(ROC)curve.Finally,the feasibility of dosimetric limitation in IMRT was assessed.Results The pancreatic volume of 30 patients was 37.6cm^(3),and 89.0% of them were involved in PTV.D_(mean) of the pancreas was 45.92Gy,and 46.45Gy,46.46Gy and 45.80Gy for the pancreatic head,body and tail,respectively.The fasting blood glucose level did not significantly change.The serum lipase levels were significantly decreased by 66% and 77%(both P<0.001),and the serum amylase levels were significantly declined by 24% and 38%(both P<0.001)at 6 and 12 months after radiotherapy.Pancreatic volumes of 22 patients was decreased by 47%within 18 months after radiotherapy.ROC curve analysis showed that pancreatic V_(45Gy) had the optimal predictive value for the decrease by 1/3 of serum lipase and amylase levels at 6 months and serum amylase level at 12 months after radiotherapy,and the cut-off value was V_(45Gy)<85%.Pancreatic D_(mean) yielded the optimal predictive value for the decrease by 2/3 of serum lipase level at 12 months after radiotherapy,and the cut-off value was D_(mean)<45.01Gy.After"whole pancreas"and"outside PTV pancreas"dose limit,V_(45Gy) of the pancreas was decreased by 11% and 7%,D_(mean) of the pancreas was declined by 2% and 2%,and D_(mean) of the pancreatic tail was decreased by 3%,respectively.Conclusions Serum lipase and amylase levels significantly decline at 6 and 12 months after adjuvant radiotherapy for gastric cancer,and pancreatic volume is decreased significantly within 18 months after radiotherapy.Pancreatic V_(45Gy)<85% and D_(mean)<45.01Gy are the dose prediction values for the decrease of serum lipase and amylase levels.The dose can be reduced to certain extent by dosimetric restriction.