Journal of Medical Physics
ORIGINAL ARTICLE
Year
: 2015  |  Volume : 40  |  Issue : 1  |  Page : 18--23

What benefit could be derived from on-line adaptive prostate radiotherapy using rectal diameter as a predictor of motion?


Richard Oates1, Suki Gill2, Farshad Foroudi3, Michael Lim Joon2, Michal Schneider5, Mathias Bressel4, Tomas Kron5 
1 Radiation Therapy Services, Peter MacCallum Cancer Centre, Bendigo; Medical Imaging and Radiation Sciences, Monash University, Melbourne, Australia
2 Radiation Oncology, Peter MacCallum Cancer Centre, Melbourne, Australia
3 Radiation Oncology, Peter MacCallum Cancer Centre, Melbourne; Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, Australia
4 Biostatistics and Clinical Trials, Peter MacCallum Cancer Centre, Melbourne, Australia
5 Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville; Physical Sciences, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia

Correspondence Address:
Richard Oates
PO Box 126, Bendigo 3552, Victoria
Australia

This study investigated a relationship between rectum diameter and prostate motion during treatment with a view to reducing planning target volume (PTV) margins for an adaptive protocol. One hundred and ninety-four cone-beam computed tomography (CBCT) images of 10 patients were used to relate rectum diameter on CBCT to prostate intrafraction displacement. A threshold rectum diameter was used to model the impact of an adaptive PTV margin on rectum and bladder dose. Potential dose escalation with a 6 mm uniform margin adaptive protocol was compared to a PTV margin of 10 mm expansion of the clinical target volume (CTV) except 6 mm posterior. Of 194 fractions, 104 had a maximum rectal diameter of ≤3.5 cm. The prostate displaced ≤4 mm in 102 of those fractions. Changing from a standard to an adaptive PTV margin reduced the volume of rectum receiving 25, 50, 60, and 70 Gy by around 12, 9, 10, and 16%, respectively and bladder by approximately 21, 27, 29, and 35%, respectively. An average dose escalation of 4.2 Gy may be possible with an adaptive prostate radiotherapy protocol. In conclusion, a relationship between the prostate motion and the diameter of the rectum on CBCT potentially could enable daily adaptive radiotherapy which can be implemented from the first fraction.


How to cite this article:
Oates R, Gill S, Foroudi F, Joon ML, Schneider M, Bressel M, Kron T. What benefit could be derived from on-line adaptive prostate radiotherapy using rectal diameter as a predictor of motion?.J Med Phys 2015;40:18-23


How to cite this URL:
Oates R, Gill S, Foroudi F, Joon ML, Schneider M, Bressel M, Kron T. What benefit could be derived from on-line adaptive prostate radiotherapy using rectal diameter as a predictor of motion?. J Med Phys [serial online] 2015 [cited 2020 Oct 19 ];40:18-23
Available from: https://www.jmp.org.in/article.asp?issn=0971-6203;year=2015;volume=40;issue=1;spage=18;epage=23;aulast=Oates;type=0