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Comparative Study
. 2009 Jul;92(1):118-24.
doi: 10.1016/j.radonc.2008.12.020. Epub 2009 Jan 30.

Volumetric-modulated arc radiotherapy for carcinomas of the anal canal: A treatment planning comparison with fixed field IMRT

Alessandro Clivio  1 , Antonella Fogliata, Alessandra Franzetti-Pellanda, Giorgia Nicolini, Eugenio Vanetti, Rolf Wyttenbach, Luca Cozzi
Affiliations
Comparative Study

Volumetric-modulated arc radiotherapy for carcinomas of the anal canal: A treatment planning comparison with fixed field IMRT

Alessandro Clivio et al. Radiother Oncol. 2009 Jul.

Abstract

Purpose: A treatment planning study was performed to compare volumetric-modulated arc radiotherapy against conventional fixed field IMRT.

Materials and methods: CT datasets of 10 patients affected by carcinoma of the anal canal were included and five plans were generated for each case: fixed beam IMRT, single (RA1)- and double (RA2)-modulated arcs with the RapidArc technique. Dose prescription was set according to a simultaneous integrated boost strategy to 59.4 Gy to the primary tumour PTVI (at 1.8 Gy/fraction) and to 49.5 Gy to risk area including inguinal nodes, PTVII. Planning objectives for PTV were minimum dose >95%, maximum dose<107%; for organs at risk (OARs): bladder (mean<45 Gy, D(2%)<56 Gy, D(30%)<35 Gy), femurs (D(2%)<47 Gy), small bowel (mean<30 Gy, D(2%)<56 Gy). MU and delivery time scored treatment efficiency.

Results: All techniques fulfilled objectives on maximum dose. Some deviations were observed on minimum dose for PTV. Uniformity (D(5)-D(95)) on PTVI resulted 6.6+/-1.4% for IMRT and ranged from 5.7+/-0.3% to 8.1+/-0.8% for RA plans (+/-1 standard deviation). Conformity index (CI(95%)) was 1.3+/-0.1 (IMRT) and 1.4+/-0.1 (all RA techniques). Bladder: all techniques resulted equivalent above 40 Gy; V(30 Gy) approximately 57% for the double arcs, approximately 61% for RA1 and approximately 65% for IMRT. Femurs: maximum dose was of the order of 41-42 Gy for all RA plans and approximately 45 Gy for IMRT. Small bowel: all techniques respected planning objectives. The number of computed MU/fraction was 1531+/-206 (IMRT), 468+/-95 (RA1), and 545+/-80 (RA2) leading to differences in treatment time: 9.4+/-1.7 min for IMRT vs. 1.1+/-0.0 min for RA1 and 2.6+/-0.0 min for double arcs.

Conclusion: RapidArc showed improvements in organs at risk and healthy tissue sparing with uncompromised target coverage when double arcs are applied. Optimal results were also achieved anyway with IMRT plans.

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