Individually optimized stereotactic radiotherapy for pancreatic head tumors: A planning feasibility study

Abstract

Aim

Aim of this study was to perform a planning feasibility analysis of a 3-level dose prescription using an IMRT-SIB technique.

Background

Radiation therapy of locally advanced pancreatic cancer should administer a minimum dose to the duodenum and a very high dose to the vascular infiltration areas to improve the possibility of a radical resection.

Materials and methods

Fifteen patients with pancreatic head adenocarcinoma and vascular involvement were included. The duodenal PTV (PTVd) was defined as the GTV overlapping the duodenal PRV. Vascular CTV (CTVv) was defined as the surface of contact or infiltration between the tumor and vessel plus a 5[[ce:hsp sp="0.25"/]]mm margin. Vascular PTV (PTVv) was considered as the CTVv plus an anisotropic margin. The tumor PTV (PTVt) was defined as the GTV plus a margin including the PTVv and excluding the PTVd. The following doses were prescribed: 30[[ce:hsp sp="0.25"/]]Gy (6[[ce:hsp sp="0.25"/]]Gy/fraction) to PTVd, 37.5[[ce:hsp sp="0.25"/]]Gy (7.5[[ce:hsp sp="0.25"/]]Gy/fraction) to PTVt, and 45[[ce:hsp sp="0.25"/]]Gy (9[[ce:hsp sp="0.25"/]]Gy/fraction) to PTVv, respectively. Treatment was planned with an IMRT technique.

Results

The primary end-point (PTVv D_mean[[ce:hsp sp="0.25"/]]>[[ce:hsp sp="0.25"/]]90%) was achieved in all patients. PTVv D_98%[[ce:hsp sp="0.25"/]]>[[ce:hsp sp="0.25"/]]90% was achieved in 6 patients (40%). OARs constraints were achieved in all patients.

Conclusions

Although the PTVv D_95%[[ce:hsp sp="0.25"/]]>[[ce:hsp sp="0.25"/]]95% objective was achieved only in 40% of patients, the study showed that in 100% of patients it was possible to administer a strongly differentiated mean/median dose. Prospective trials based on clinical application of this strategy seem to be justified in selected patients without overlap between PTVd and PTVv.