Comparison of the dose escalation potential for two hypofractionated radiotherapy regimens for locally advanced pancreatic cancer. (May 2019)

• Record Type: Journal Article
• Authors: Bertholet, Jenny; Hunt, Arabella; Dunlop, Alex; Bird, Thomas; Mitchell, Robert A.; Oelfke, Uwe; Nill, Simeon; Aitken, Katharine
• Is Part Of: Clinical and translational radiation oncology. Volume 16(2019)
• Page Start: 21
• Page End: 27
• Publication Date: 2019-05
• Subjects: Pancreatic cancer -- SBRT -- Hypofractionation -- Dose escalation -- Treatment planning; Cancer -- Radiotherapy -- Periodicals; Oncology -- Periodicals; Cancer -- Radiotherapy; Oncology; Radiation Oncology; Neoplasms -- radiotherapy; Translational Medical Research; Periodicals; Electronic journals; Periodicals; 616.9940642
• DOI: 10.1016/j.ctro.2019.03.001
• Languages: English
• ISSNs: 2405-6308

Abstract

Highlights: The dose for hypofractionated RT for LAPC is limited by the proximity of OAR. Uniform target coverage by a BED of 54 Gy is easier in 15 than in 5 fractions. But the dose escalation potential to a BED of 100 Gy is similar in 5 or 15 fractions. Larger tumour sub-volumes may receive a high dose on days with favourable anatomy. Abstract: Objectives: To determine the potential for dose escalation to a biological equivalent dose BED10 ≅ 100 Gy in hypofractionated radiotherapy for locally advanced pancreatic cancer (LAPC). Materials and methods: Ten unselected LAPC patients were retrospectively included in the study. Two fractionation regimens were compared (5 and 15 fractions). The aim was to cover 95% of the Planning Target Volume (PTV) with a BED10 = 54 Gy (base dose = 33 Gy in 5 fractions, 42.5 Gy in 15 fractions) whilst respecting organs-at-risk (OAR) constraints. Once the highest PTV coverage was achieved dose escalation to a BED10 ≅ 100 Gy (escalated dose = 50 Gy in 5 fractions, 67.5 Gy in 15 fractions) was attempted, limiting the PTV maximum dose to 130% of the escalated dose. Results: In 5 fractions, 95% PTV coverage by both base and escalated doses could be achieved for one patient with PTV more than 1 cm away from OAR. 95% and 90% PTV coverage by the base dose was achieved in one and two patients respectively. In all other patients, coverage even by the base dose had to be compromised to comply with OAR constraints. In 15 fractions, 95% PTV coverage by the base dose was feasible for all patients except one. Dose escalation allowed improvement in target coverage by the base dose in both fractionation regimen whilst covering a sub-volume of the PTV with a BED10 ≅ 100 Gy. Both fractionation schemes were equivalent in terms of dose escalation potential. Conclusion: LAPC patients with OAR close to the PTV are generally not eligible for hypofractionation with dose escalation. However, this planning study shows that it is possible to cover PTV sub-volumes with a BED10 ≅ 100 Gy in addition to delivering a BED10 = 54 Gy to 90–95% of the PTV as commonly prescribed to this population. Combined with an adaptive approach, this may maximize PTV coverage by a high BED on days with favourable anatomy.