Evaluation of pancreatic subclinical dysfunction and sparing of pancreas after intensity-modulated radiation therapy for gastric cancer / 中华放射肿瘤学杂志

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 45 Gy 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 37.6 cm 3, and 89.0% of them were involved in PTV. D mean of the pancreas was 45.92 Gy, and 46.45 Gy, 46.46 Gy and 45.80 Gy 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<45.01 Gy. 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<45.01 Gy 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.