胃癌调强放疗后胰腺亚临床功能损伤评估与保护

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...

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

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 37.6cm³,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.