Can Conformity-Based Volumetric Modulated Arc Therapy Improve Dosimetry and Speed of Delivery in Radiation Therapy to Lumbosacral Spine Compared with Conventional Techniques?

Joanna Javor; Meagan Robbins; Tara Rosewall; Tim Craig; Conrad Joseph Villafuerte; Bernard Cummings; Laura Dawson

doi:10.1016/j.jmir.2020.04.003

Can Conformity-Based Volumetric Modulated Arc Therapy Improve Dosimetry and Speed of Delivery in Radiation Therapy to Lumbosacral Spine Compared with Conventional Techniques?

J Med Imaging Radiat Sci. 2020 Sep;51(3):404-410. doi: 10.1016/j.jmir.2020.04.003. Epub 2020 May 18.

Authors

Joanna Javor¹, Meagan Robbins², Tara Rosewall³, Tim Craig³, Conrad Joseph Villafuerte⁴, Bernard Cummings³, Laura Dawson³

Affiliations

¹ Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada. Electronic address: Joanna.javor@rmp.uhn.ca.
² Eastern Health, Newfoundland and Labrador, St. John's, Canada.
³ Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada.
⁴ Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada.

PMID: 32439283
DOI: 10.1016/j.jmir.2020.04.003

Abstract

Purpose: Volumetric modulated arc therapy (VMAT) has generally been perceived as too time and resource intensive for palliative radiation therapy mainly because of the need for extensive organs at risk contouring. Dose-limiting conformity-based objectives can be automatically generated and are commonly used to conform isodoses closely around the target volumes during inverse planning. The aim of this study was to determine if conformity-based objectives can be used to create VMAT plans for lumbosacral spine palliative radiation therapy without organs at risk contours, which will improve conformity, dose homogeneity, and speed of delivery compared with standard forward planning approaches.

Methods: A total of 25 patients were retrospectively replanned using three different planning techniques: (1) anterior-posterior parallel opposed pair (POP); (2) single isocenter anterior-posterior half-beam block junctioned to three fields, posterior and two laterals (JUNC); and (3) VMAT single arc. Treatment volume included L1-S5 vertebrae prescribed to 20 Gy in five fractions. Conformality index, homogeneity index, contour, planning, and treatment time were compared for each technique.

Results: Planning target volume V95 ≥95% was maintained for all 75 replans. VMAT was superior to POP and JUNC in terms of conformality (POP 2.0 vs. JUNC 1.8 vs. VMAT 1.2; P < .01) and homogeneity (POP 1.1 vs. JUNC 1.1 vs. VMAT 1.0; P < .01). Planning times for POP were the lowest (3.2 minutes). VMAT and POP had similar delivery times (1.5 minutes), which were approximately half the JUNC delivery time (3.2 minutes).

Conclusions: Conformity-based VMAT was dosimetrically superior to conventional field-based planning and reduced delivery time. This reduction in normal tissue dose as well as reduced time spent on the treatment couch can potentially improve the quality of life in palliative patients receiving radiotherapy to the lumbosacral spine.

Keywords: Palliative radiotherapy; quality of life; volumetric modulated arc therapy.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Bone Neoplasms / radiotherapy*
Bone Neoplasms / secondary
Humans
Lumbar Vertebrae
Organs at Risk
Palliative Care
Quality of Life
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted / methods*
Radiotherapy, Intensity-Modulated / methods*
Retrospective Studies
Sacrum