Volumetric modulated arc therapy with simultaneous integrated boost for locally advanced rectal cancer.

To report the feasibility of volumetric modulated arc therapy (VMAT) for neoadjuvant radiotherapy in locally advanced rectal cancer in a dose-escalation protocol and simultaneous integrated boost (SIB) approach. Moreover, the VMAT technique was compared with three-dimensional conformal radiotherapy (3D-CRT) and fixed-field intensity modulated radiotherapy (IMRT), in terms of target coverage and irradiation of organs at risk. Eight patients with locally advanced rectal cancer were treated with the SIB-VMAT technique. The VMAT plans were compared with 3D-CRT and IMRT techniques in terms of several clinically dosimetric parameters. The number of monitor units and the delivery time were analysed to score the treatment efficiency. All plans were verified in a dedicated solid water phantom using a two-dimensional array of ionisation chambers. All techniques meet the prescription goal for planning target volume coverage, with VMAT showing the highest level of conformality. VMAT is associated with 40, 53 and 58% reduction in the percentage of volume of small bowel irradiated to 30, 40 and 50Gy, compared with 3D-CRT. No significant differences were found with respect to SIB-IMRT. VMAT plans showed a significant reduction of monitor units by nearly 20% with respect to IMRT and reduced treatment time from 14 to 5min for a single fraction. SIB-VMAT plans can be planned and carried out with high quality and efficiency for rectal cancer, providing similar sparing of organs at risk to SIB-IMRT and resulting in the most efficient treatment option. SIB-VMAT is currently our standard approach for radiotherapy of locally advanced rectal cancer.

Cilla S ，Caravatta L ，Picardi V ，Sabatino D ，Macchia G ，Digesù C ，Deodato F ，Massaccesi M ，De Spirito M ，Piermattei A ，Morganti AG ... -  《-》

Applicator-guided volumetric-modulated arc therapy for low-risk endometrial cancer.

The aim of this study was to report the feasibility of volumetric-modulated arc therapy (VMAT) in the postoperative irradiation of the vaginal vault. Moreover, the VMAT technique was compared with 3D conformal radiotherapy (3D-CRT) and fixed-field intensity-modulated radiotherapy (IMRT), in terms of target coverage and organs at risk sparing. The number of monitor units and the delivery time were analyzed to score the treatment efficiency. All plans were verified in a dedicated solid water phantom using a 2D array of ionization chambers. Twelve patients with endometrial carcinoma who underwent radical hystero-adenexectomy and fixed-field IMRT treatments were retrospectively included in this analysis; for each patient, plans were compared in terms of dose-volume histograms, homogeneity index, and conformity indexes. All techniques met the prescription goal for planning target volume coverage, with VMAT showing the highest level of conformity at all dose levels. VMAT resulted in significant reduction of rectal and bladder volumes irradiated at all dose levels compared with 3D-CRT. No significant differences were found with respect to IMRT. Moreover, a significant improvement of the dose conformity was reached by VMAT technique not only at the 95% dose level (0.74 vs. 0.67 and 0.62) but also at 50% and 75% levels of dose prescription. In addition, VMAT plans showed a significant reduction of monitor units by nearly 28% with respect to IMRT, and reduced treatment time from 11 to <3 minutes for a single 6-Gy fraction. In conclusion, VMAT plans can be planned and carried out with high quality and efficiency for the irradiation of vaginal vault alone, providing similar or better sparing of organs at risk to fixed-field IMRT and resulting in the most efficient treatment option. VMAT is currently our standard approach for radiotherapy of low-risk endometrial cancer.

Cilla S ，Macchia G ，Sabatino D ，Digesù C ，Deodato F ，Piermattei A ，De Spirito M ，Morganti AG ... -  《-》

Assessing the feasibility of volumetric-modulated arc therapy using simultaneous integrated boost (SIB-VMAT): An analysis for complex head-neck, high-risk prostate and rectal cancer cases.

Intensity-modulated radiotherapy (IMRT) allowed the simultaneous delivery of different doses to different target volumes within a single fraction, an approach called simultaneous integrated boost (SIB). As consequence, the fraction dose to the boost volume can be increased while keeping low doses to the elective volumes, and the number of fractions and overall treatment time will be reduced, translating into better radiobiological effectiveness. In recent years, volumetric-modulated arc therapy (VMAT) has been shown to provide similar plan quality with respect to fixed-field IMRT but with large reduction in treatment time and monitor units (MUs) number. However, the feasibility of VMAT when used with SIB strategy has few investigations to date. We explored the potential of VMAT in a SIB strategy for complex cancer sites. A total of 15 patients were selected, including 5 head-and-neck, 5 high-risk prostate, and 5 rectal cancer cases. Both a double-arc VMAT and a 7-field IMRT plan were generated for each case using Oncentra MasterPlan treatment planning system for an Elekta Precise linac. Dosimetric indexes for targets and organs at risk (OARs) were compared based on dose-volume histograms. Conformity index, homogeneity index, and dose-contrast index were used for target analyses. The equivalent uniform doses and the normal tissue complication probabilities were calculated for main OARs. MUs number and treatment time were analyzed to score treatment efficiency. Pretreatment dosimetry was performed using 2-dimensional (2D)-array dosimeter. SIB-VMAT plans showed a high level of fluence modulation needed for SIB treatments, high conformal dose distribution, similar target coverage, and a tendency to improve OARs sparing compared with the benchmark SIB-IMRT plans. The median treatment times reduced from 13 to 20 minutes to approximately 5 minutes for all cases with SIB-VMAT, with a MUs reduction up to 22.5%. The 2D-array ion-chambers' measurements reported an agreement of more than 95% for a criterion of 3% to 3mm. SIB-VMAT was able to combine the advantages of conventional SIB-IMRT with its highly conformal dose distribution and OARs sparing and the advantages of 3D-conformal radiotherapy with its fast delivery.

Cilla S ，Deodato F ，Digesù C ，Macchia G ，Picardi V ，Ferro M ，Sallustio G ，De Spirito M ，Piermattei A ，Morganti AG ... -  《-》

Optimising the dosimetric quality and efficiency of post-prostatectomy radiotherapy: a planning study comparing the performance of volumetric-modulated arc therapy (VMAT) with an optimised seven-field intensity-modulated radiotherapy (IMRT) technique.

The purpose of this study was to compare and evaluate radiotherapy treatment plans using volumetric modulated arc therapy (VMAT) and intensity modulated radiotherapy (IMRT) for post-prostatectomy radiotherapy. The quality of radiotherapy plans for 10 patients planned and treated with a seven-field IMRT technique for biochemical failure post-prostatectomy were subsequently compared with 10 prospectively planned single-arc VMAT plans using the same computed tomography data set and treatment planning software. Plans were analysed using parameters to assess for target volume coverage, dose to organs at risk (OAR), biological outcomes, dose conformity and homogeneity, as well as the total monitor units (MU), planning and treatment efficiency. The mean results for the study population are reported for the purpose of comparison. For IMRT, the median dose to the planning target volume, V(95%) and D(95%) was 71.1 Gy, 98.9% and 68.3 Gy compared with 71.2 Gy, 99.2% and 68.6 Gy for VMAT. There was no significant difference in the conformity index or homogeneity index. The VMAT plans achieved better sparing of the rectum and the left and right femora with a reduction in the median dose by 7.9, 6.3 and 3.6 Gy, respectively. The total number of monitor units (MU) was reduced by 24% and treatment delivery time by an estimated 3 min per fraction without a significant increase in planning requirements. VMAT can achieve post-prostatectomy radiotherapy plans of comparable quality to IMRT with the potential to reduce dose to OAR and improve the efficiency of treatment delivery.

Nguyen BT ，Hornby C ，Kron T ，Cramb J ，Rolfo A ，Pham D ，Haworth A ，Tai KH ，Foroudi F ... -  《-》

Volumetric modulated arc therapy vs. IMRT for the treatment of distal esophageal cancer.

Several studies have demonstrated that volumetric modulated arc therapy (VMAT) has the ability to reduce monitor units and treatment time when compared with intensity-modulated radiation therapy (IMRT). This study aims to demonstrate that VMAT is able to provide adequate organs at risk (OAR) sparing and planning target volume (PTV) coverage for adenocarcinoma of the distal esophagus while reducing monitor units and treatment time. Fourteen patients having been treated previously for esophageal cancer were planned using both VMAT and IMRT techniques. Dosimetric quality was evaluated based on doses to several OARs, as well as coverage of the PTV. Treatment times were assessed by recording the number of monitor units required for dose delivery. Body V(5) was also recorded to evaluate the increased volume of healthy tissue irradiated to low doses. Dosimetric differences in OAR sparing between VMAT and IMRT were comparable. PTV coverage was similar for the 2 techniques but it was found that IMRT was capable of delivering a slightly more homogenous dose distribution. Of the 14 patients, 12 were treated with a single arc and 2 were treated with a double arc. Single-arc plans reduced monitor units by 42% when compared with the IMRT plans. Double-arc plans reduced monitor units by 67% when compared with IMRT. The V(5) for the body was found to be 18% greater for VMAT than for IMRT. VMAT has the capability to decrease treatment times over IMRT while still providing similar OAR sparing and PTV coverage. Although there will be a smaller risk of patient movement during VMAT treatments, this advantage comes at the cost of delivering small doses to a greater volume of the patient.

Van Benthuysen L ，Hales L ，Podgorsak MB 《-》