Image-guided high precision proton irradiation of pancreatic adenocarcinoma using a gold fiducial marker


Image-guided high precision proton irradiation of pancreatic adenocarcinoma using a gold fiducial marker

Stefanowicz, S.; Thiele, J.; Hoffmann, A.; Troost, E.

Introduction
The inter- and intra-fractional position variability of the target volume and the abdominal organs and their poor visibility on currently used imaging modalities for proton beam irradiation, make high-precision radiation therapy of pancreatic cancer challenging. Moreover, due to the specific physical properties of protons, an accurate patient positioning is mandatory. This can be accomplished by image-guided setup, possibly aided by implanted fiducial markers. Here we present our first experience treating a pancreatic adenocarcinoma patient using gold fiducial markers and passive scattered proton therapy (PSPT).

Material and Methods
A patient with a primary irresectable adenocarcinoma of the pancreatic head (cT4N1M0) underwent neoadjuvant radiochemotherapy (50.4 Gy(RBE) in 28 fractions, weekly gemcitabine). Prior to treatment planning, three radiopaque fiducial markers (Gold AnchorTM, Naslund Medical AB, Sweden) were endoscopically implanted in the proximity of the tumour. The radiation treatment plan was generated in XiO (Elekta, Sweden) using two ventro-dorsally opposing double-scattered proton beams such that 95% of the prescribed dose covered the clinical target volume (CTV). Orthogonal X-rays were acquired for daily positioning, and on a weekly basis, target volume coverage and potential anatomical changes were assessed using an in-room dual-energy/4D-CT (Somatom Definition AS, Siemens Healthineers, Germany). In order to estimate the inter- and intra-fractional motion of the markers and to recalculate the delivered dose, the per-treatment CTs were rigidly fused to the planning CT using Raystation 4.7 (RaySearch Laboratories AB, Sweden), and the CTV and the organs at risk were copied and if necessary adapted.

Results
The patient completed radiochemotherapy with grade 1 nausea only. The markers did not migrate into surrounding tissues and inter- as well as intra-fractional baseline shifts of < 1 cm in all spatial directions (LR, AP, CC) were measured. In all recalculated plans the dose specification for the CTV and the organ at risks were achieved. However, the mean value of all average doses to the kidneys was increased by 25% (right, range of 17% - 37%) and 33% (left, range of -0.6% - 51%) in comparison to the initial treatment plan, but was within the dose constraints (< 15 Gy).

Conclusion
There was no significant difference between the prescribed and the delivered dose based on the recalculation. The gold fiducial markers remained stable and baseline shifts were limited [1]. Fiducial markers enable accurate positioning of the pancreas, however, markers with minor perturbation behaviour for proton therapy may be preferred.

References
[1] Wysocka, B. et al.: Interfraction and Respiratory Organ Motion During Conformal Radiotherapy in Gastric Cancer, Int. J. Radiation Oncology Biol. Phys., 2010, 77 (1), pp. 53 – 59.

  • Lecture (Conference)
    4D Workshop 2016, 08.-09.12.2016, Groningen, Niederlande

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Publ.-Id: 24295