Dosimetric benefit of an adaptive treatment by means of plan selection for rectal cancer patients in both short and long course radiation therapy

• Published in: Radiation oncology (London, England) Vol. 15; no. 1; p. 13
• Main Authors: de Jong, R, Visser, J, Crama, K F, van Wieringen, N, Wiersma, J, Geijsen, E D, Bel, A
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 13-01-2020; BioMed Central; BMC
• Subjects: Adaptive radiotherapy; Adaptive treatment; Bladder; Cancer; Cancer patients; Cancer therapies; Care and treatment; CAT scans; Colorectal cancer; Computed tomography; Development and progression; Diagnostic imaging; Dosage; Dose-response relationship; Ethics; Health care facilities; Library of plans; Lymphatic system; Medical ethics; Medical imaging; Medical research; Methods; Organs; Parameters; Patient outcomes; Patients; Plan of the day; Plan selection; Planning; Radiation; Radiation (Physics); Radiation therapy; Radiotherapy; Rectal cancer; Rectum; Schedules; Small intestine; Netherlands; Adaptive treatment; Plan of the day; Rectal cancer; Plan selection; Library of plans; Normal tissue sparing; Adaptive radiotherapy
• ISSN: 1748-717X; 1748-717X
• DOI: 10.1186/s13014-020-1461-3

To compare target coverage and dose to the organs at risk in two approaches to rectal cancer: a clinically implemented adaptive radiotherapy (ART) strategy using plan selection, and a non-adaptive (non-ART) strategy.
The inclusion of the first 20 patients receiving adaptive radiotherapy produced 10 patients with a long treatment schedule (25x2Gy) and 10 patients with a short schedule (5X5Gy). We prepared a library of three plans with different anterior PTV margins to the upper mesorectum, and selected the most appropriate plan on daily Conebeam CT scans (CBCT). We also created a non-adaptive treatment plan with a 20 mm margin. Bowel bag, bladder and target volume were delineated on CBCT. Daily DHVs were calculated based on the dose distribution of the selected and non-adaptive plans. Coverage of the target volume was compared per fraction between the ART and non-ART plans, as was the dose to the bladder and small bowel, assessing the following dose levels: V15Gy, V30Gy, V40Gy, V15Gy and V95% for long treatment schedules, and V15Gy and V95% for short ones.
Target volume coverage was maintained from 98.3% (non-ART) to 99.0% (ART)(p = 0.878). In the small bowel, ART appeared to have produced significant reductions in the long treatment schedule at V15Gy, V40Gy, V45Gy and V95% (p <  0.05), but with small absolute differences. The DVH parameters tested for the short treatment schedule did not differ significantly. In the bladder, all DVH parameters in both schedules showed significant reductions (p <  0.05), also with small absolute differences.
The adaptive treatment maintained target coverage and reduced dose to the organs at risk.
Medical Research Involving Human Subjects Act (WMO) does not apply to this study and was retrospectively approved by the Medical Ethics review Committee of the Academic Medical Center, W19_194 # 19.233.