The analysis of absorbed dose by pancreas during gastric cancer radiotherapy

Introduction: The toxicity of radiotherapy is a very important issue in the everyday work of radiation oncologist. The tolerance to certain doses of radiotherapy in organs at risk determines the safety of radiotherapy. Despite the increasing number of publications concerning the injury of the pancreas after radiotherapy, this organ does not have common directives. We decided to reanalyse our previously published data in terms of the dose of radiation absorbed by the pancreas to determine a dose-effect relationship with the use of radiation-induced hypoamylasaemia and hypolipasaemia. Materials and methods: We reanalysed a group of 127 gastric cancer patients after preoperative or postoperative chemoradiotherapy who were treated with a total dose of 45 Gy administered in 25 fractions. To identify the absorbed doses, the pancreas was contoured based on the CT scans used for radiotherapy planning and divided into anatomical parts: the head, the body and the tail. Results: We found that 80% of the whole pancreatic volume absorbed at least 44.5 Gy. The body, tail and head absorbed 100%, 90% and 70% of the abovementioned dose, respectively. The mean dose absorbed by the whole pancreas ranged from 32 to 48 Gy, with a mean of 44 Gy. A total dose of 45 Gy administered to gastric cancer patients can lead to subclinical insufficiency of the pancreas (hypolipasaemia and hypoamylasaemia). This dose is not able to cause symptomatic damage to the pancreas.