Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2018 May;91(1085):20170654.
doi: 10.1259/bjr.20170654. Epub 2018 Mar 6.

Target volume motion during anal cancer image guided radiotherapy using cone-beam computed tomography

Corrinne J Brooks  1 , Laurence Bernier  2 , Vibeke N Hansen  1 , Diana M Tait  2
Affiliations

Target volume motion during anal cancer image guided radiotherapy using cone-beam computed tomography

Corrinne J Brooks et al. Br J Radiol. 2018 May.

Abstract

Objective: Literature regarding image-guidance and interfractional motion of the anal canal (AC) during anal cancer radiotherapy is sparse. This study investigates interfractional AC motion during anal cancer radiotherapy.

Methods: Bone matched cone beam CT (CBCT) images were acquired for 20 patients receiving anal cancer radiotherapy allowing population systematic and random error calculations. 12 were selected to investigate interfractional AC motion. Primary anal gross tumour volume and clinical target volume (CTVa) were contoured on each CBCT. CBCT CTVa volumes were compared to planning CTVa. CBCT CTVa volumes were combined into a CBCT-CTVa envelope for each patient. Maximum distortion between each orthogonal border of the planning CTVa and CBCT-CTVa envelope was measured. Frequency, volume and location of CBCT-CTVa envelope beyond the planning target volume (PTVa) was analysed.

Results: Population systematic and random errors were 1 and 3 mm respectively. 112 CBCTs were analysed in the interfractional motion study. CTVa varied between each imaging session particularly T location patients of anorectal origin. CTVa border expansions ≥ 1 cm were seen inferiorly, anteriorly, posteriorly and left direction. The CBCT-CTVa envelope fell beyond the PTVa ≥ 50% imaging sessions (n = 5). Of these CBCT CTVa distortions beyond PTVa, 44% and 32% were in the upper and lower thirds of PTVa respectively.

Conclusion: The AC is susceptible to volume changes and shape deformations. Care must be taken when calculating or considering reducing the PTV margin to the anus. Advances in knowledge: Within a limited field of research, this study provides further knowledge of how the AC deforms during anal cancer radiotherapy.

PubMed Disclaimer

Figures

Figure 1.
Figure 1.
Diagram (a, b) describe the maximum distortion between the borders of the CBCT CTVa envelope (red contour) and the planning CTVa (blue contour). The corresponding CT contours are shown in (c, d). Planning CTVa (light green contour), CBCT CTVa envelope (orange contour) and planning PTV (pink contour) are presented. CBCT, cone beam CT; CTV, clinical target volume; PTV, planning target volume.
Figure 2.
Figure 2.
Observed change in CBCT CTVa volume compared to the planning CTVa for each patient for each fraction. Difference is shown as a percentage. CBCT, cone beam CT; CTV, clinical target volume.
Figure 3.
Figure 3.
Images (a, b) show the planning CT with the planning CTVa (red) and CBCT CTVa (blue). Images (c,d) show the corresponding CBCT for the derived CBCT CTVa (blue). N.B These images were matched on bone. CBCT, cone beam CT; CTV, clinical target volume.
Figure 4.
Figure 4.
Frequency (%) of CBCT CTVa outside of planning PTVa in one or more directions for individual cases. CBCT, cone beam CT; CTV, clinical target volume; PTV, clinical planning target volume.
See this image and copyright information in PMC

References

    1. James RD, Glynne-Jones R, Meadows HM, Cunningham D, Myint AS, Saunders MP, et al. . Mitomycin or cisplatin chemoradiation with or without maintenance chemotherapy for treatment of squamous-cell carcinoma of the anus (ACT II): a randomised, phase 3, open-label, 2 × 2 factorial trial. Lancet Oncol 2013; 14: 516–24. doi: 10.1016/S1470-2045(13)70086-X - DOI - PubMed
    1. Muirhead R, Drinkwater K, O’Cathail SM, Adams R, Glynne-Jones R, Harrison M, et al. . Initial results from the royal college of radiologists’ UK national audit of anal cancer radiotherapy 2015. Clin Oncol 2017; 29: 188–97. doi: 10.1016/j.clon.2016.10.005 - DOI - PMC - PubMed
    1. Gilbert DC, Drinkwater K, O’Cathail SM, Adams R, Glynne-Jones R, Harrison M, et al. . Stepwise multicenter introduction of intensity modulated radiation therapy for anal cancer in the United Kingdom: from consensus guidance to large-scale prospective audit, prior to future clinical trials. Int J Radiat Oncol Biol Phys 2016; 96: S105–S106. doi: 10.1016/j.ijrobp.2016.06.260 - DOI
    1. Kachnic LA, Winter K, Myerson RJ, Goodyear MD, Willins J, Esthappan J, et al. . RTOG 0529: a phase 2 evaluation of dose-painted intensity modulated radiation therapy in combination with 5-fluorouracil and mitomycin-C for the reduction of acute morbidity in carcinoma of the anal canal. Int J Radiat Oncol Biol Phys 2013; 86: 27–33. doi: 10.1016/j.ijrobp.2012.09.023 - DOI - PMC - PubMed
    1. International Commission on Radiation Units and Measurements. Prescribing, recording and reporting beam therapy Report No.: 50. 1993. doi: 10.1118/1.597396 - DOI