Evaluation of pancreatic subclinical dysfunction and sparing of pancreas after intensity-modulated radiation therapy for gastric cancer
Sun Guanyu, Ma Yifu, Ma Jiayan, Guo Qiuchen, Zhou Chengliang, Chen Li, Yang Yongqiang, Qian Jianjun, Zhang Liyuan, Tian Ye
Department of Radiation Oncology,Second Affiliated Hospital of Soochow University;Institute of Radiotherapy& Oncology, Soochow University;Suzhou Key Laboratory for Radiation Oncology, Suzhou 215004, China
Abstract：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. Dmean 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 V45Gy 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 V45Gy<85%. Pancreatic Dmean 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 Dmean<45.01Gy. After"whole pancreas" and"outside PTV pancreas" dose limit, V45Gy of the pancreas was decreased by 11% and 7%, Dmean of the pancreas was declined by 2% and 2%, and Dmean 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 V45Gy<85% and Dmean<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.
Sun Guanyu,Ma Yifu,Ma Jiayan et al. Evaluation of pancreatic subclinical dysfunction and sparing of pancreas after intensity-modulated radiation therapy for gastric cancer[J]. Chinese Journal of Radiation Oncology, 2022, 31(2): 153-159.
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