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Radiation Oncology

, 4:48

First Online: 25 October 2009Received: 15 July 2009Accepted: 25 October 2009


Background-PurposeRadiotherapy RT volumes for anal cancer are large and of moderate complexity when organs at risk OAR such as testis, small bowel and bladder are at least partially to be shielded. Volumetric intensity modulated arc therapy VMAT might provide OAR-shielding comparable to step-and-shoot intensity modulated radiotherapy IMRT for this tumor entity with better treatment efficiency.

Materials and methodsBased on treatment planning CTs of 8 patients, we compared dose distributions, comformality index CI, homogeneity index HI, number of monitor units MU and treatment time TTT for plans generated for VMAT, 3D-CRT and step-and-shoot-IMRT optimized based on Pencil Beam PB or Monte Carlo MC dose calculation for typical anal cancer planning target volumes PTV including inguinal lymph nodes as usually treated during the first phase 0-36 Gy of a shrinking field regimen.

ResultsWith values of 1.33 ± 0.21-1.26 ± 0.05-1.3 ± 0.02 and 1.39 ± 0.09, the CI-s for IMRT PB-Corvus-PB-Hyperion-MC-Hyperion and VMAT are better than for 3D-CRT with 2.00 ± 0.16. The HI-s for the prescribed dose HI36 for 3D-CRT were 1.06 ± 0.01 and 1.11 ± 0.02 for VMAT, respectively and 1.15 ± 0.02-1.10 ± 0.02-1.11 ± 0.08 for IMRT PB-Corvus-PB-Hyperion-MC-Hyperion. Mean TTT and MU-s for 3D-CRT is 220s-225 ± 11MU and for IMRT PB-Corvus-PB-Hyperion-MC-Hyperion is 575s-1260 ± 172MU, 570s-477 ± 84MU and 610s748 ± 193MU while TTT and MU for two-arc-VMAT is 290s-268 ± 19MU.

ConclusionVMAT provides treatment plans with high conformity and homogeneity equivalent to step-and-shoot-IMRT for this mono-concave treatment volume. Short treatment delivery time and low primary MU are the most important advantages.

Electronic supplementary materialThe online version of this article doi:10.1186-1748-717X-4-48 contains supplementary material, which is available to authorized users.

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Autor: Florian Stieler - Dirk Wolff - Frank Lohr - Volker Steil - Yasser Abo-Madyan - Friedlieb Lorenz - Frederik Wenz - Sabine M

Fuente: https://link.springer.com/

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