A new delineation method research of the clinical target volume for pancreatic cancer adjuvant radiotherapy

Abstract

PurposeThe purpose of this work was to establish a map model of the local recurrence location after pancreatic cancer resection and to generate a new delineation method of clinical target volume, with the aim to effectively improve the adjuvant radiotherapeutic gain ratio. Methods and materialsThe clinical and imaging data of 48 patients with resected pancreatic head cancer and pancreatic body cancer with local recurrences were collected. Local recurrences were all plotted with reference to the geometric centre of the local recurrent foci. Based on the coordinates of the local recurrences with respect to the celiac artery or the superior mesenteric artery, a three-dimensional local recurrence map model was established on the computed tomography image. The adjuvant radiation clinical target volumes encompassing 90% of all local failures and encompassing 90% of postoperative pancreatic head cancer local failures were created respectively. This new delineation method and RTOG 0848 protocol were applied in five simulated cases, then corresponding types of target volumes and plans were generated for comparison. ResultsThe clinical target volume encompassing 90% of all local failures was generated by expanding the combined celiac artery and superior mesenteric artery contour by 1.4cm superior, 1.9cm inferior, 2.6cm left-lateral, 3.1cm right-lateral, 1.9cm anterior and 1.6cm posterior. The corresponding expansions of clinical target volume encompassing 90% of postoperative pancreatic head cancer local failures were 1.4cm, 1.4cm, 2.1cm, 3.1cm, 1.6cm and 2.0cm. The volumes of “new” target PTV-90_edited, PTV-90_H_edited, and the standard target PTV_edited were 217.64±58.67 cm3, 207.78±50.94 cm3 and 320.72±50.94 cm3 in simulated cases. Comparison showed that the “new” target volumes were much smaller than the standard volumes per RTOG 0848 protocol, and the dose received by organs at risk was also lower in the “new” plans. ConclusionsA majority of postoperative local recurrences in patients with pancreatic head and body cancer are contained within a smaller region surrounding the celiac artery and superior mesenteric artery. The “new” volumes targeting high risk local failures may allow dose escalation and enhanced local control while minimizing radiation-related toxicity.