Feasibility study of volumetric modulated arc therapy for the treatment of retroperitoneal sarcomas

Abstract

BackgroundRadiotherapy for retroperitoneal sarcomas remains controversial and a technical challenge considering the threshold of contiguous critical organs tolerance. We performed consecutive RapidArc dosimetric plans in preoperative or postoperative setting.MethodsA dosimetric study was carried out from six preoperative (group A) and four postoperative (group B) CT-scans, performed in 7 patients.Prescribed dose was 45 and 50 Gy for groups A and B, respectively. The planning target volume (PTV) was defined as the clinical target volume (CTV) plus 5 mm. The CTV encompassed the gross tumor volume (GTV) plus 10 mm or the tumoral bed. The dosimetric plans were optimized on a RapidArc Eclipse console using the progressive resolution algorithm, PRO version 8.8. Normalization method allowed the coverage of 99% of the PTV by 95% of the dose.ResultsMean PTV were 2318.5 ± 2223.9 cc [range 348-6198 cc] and 698.3 ± 216.6 cc [range 463 -933 cc] for groups A and B, respectively. Plans were optimized for single arcs in group B and for single or two arcs in group A. The contralateral kidney volume receiving 5 Gy (V5Gy) was 21.5 ± 23.3% [range 0-55%] and 3.1 ± 2.6% [range 0-7.3%] for groups A and B, respectively. The mean dose received by 1% of the kidney (D1%) was 5.6 ± 2.4 Gy [range 3.6 -7.6 Gy] for group A and 5.4 ± 0.7 Gy [range 4.3-6 Gy] for group B. The volume of small bowel excluding the PTV (small bowel-PTV) that received 40 Gy and 30 Gy (V40Gy and V30Gy) in group A were 7.5 ± 4.4% [range 5.4-14.1%] and 18.5 ± 7.1% [range 10-30.4%], respectively.In group B, small bowel-PTV V40Gy and V30Gy were 4.7 ± 3.3% [range 3.3-8%] and 21.6 ± 7.5% [range 9.4-30%] respectively. In a second step, we treated two patients in the postoperative group. Treatment time delivery with one arc was 74 seconds. No severe acute toxicity was observed.ConclusionRapidArc technology for retroperitoneal sarcomas showed acceptable dosimetric results in preoperative or postoperative clinical situation. From the first treated patients, acute tolerability was good to excellent.

Volumetric‐modulated arc therapy versus intensity‐modulated radiotherapy for large volume retroperitoneal sarcomas: A comparative analysis of dosimetric and treatment delivery parameters

“…The homogeneity index ( was 0.068 and 0.066 for VMAT and IMRT, respectively. This is comparable to earlier reported RPS studies (D5%–D95%) . .…”

“…VMAT is an improved and more efficient method of delivering IMRT as demonstrated for other tumor sites . A single feasibility study investigating the use of VMAT for treatment of RPS is reported; however, they did not perform a direct comparison of VMAT to IMRT as it has been done for other tumor sites. Therefore, it is important to conduct and report dosimetric comparison studies of VMAT and IMRT in RPS, such that evidence can guide adoption of this technique in clinical practice.…”

“…One potential solution to overcome these issues is to use volumetric‐modulated arc therapy (VMAT) . Llacer‐Moscardo et al reported on feasibility of VMAT in seven preoperative and three postoperative RPS cases and implied it is superior than IMRT‐based plans . However, a direct comparison study of VMAT versus IMRT treatment planning within the same cohort of patients has not been reported.…”

Volumetric modulated arc therapy: a review of current literature and clinical use in practice

“…VMAT plans achieved better conformity and OAR sparing (left kidney, liver, stomach, small bowel and duodenum) compared with fixed field IMRT (SW). Llacer-Moscardo et al [150] performed a dosimetric feasibility study of VMAT in retroperitoneal sarcoma and found acceptable target volume coverage and OAR sparing. Benthuysen et al [151] evaluated VMAT in distal oesophageal cancers and found comparable PTV coverage and OAR sparing to fixed field IMRT with a 42-67% reduction in MU, but greater low dose radiation to the body (V5 Gy 18% greater for VMAT plans).…”

Critical appraisal of volumetric-modulated arc therapy compared with electrons for the radiotherapy of cutaneous Kaposi’s sarcoma of lower extremities with bone sparing

“…Many indications can benefit from the RA technology, and, regarding sarcomas, little has been published to date. LlacerMoscardo et al [11] investigated the potential of this VMAT approach for huge retroperitoneal sarcoma, this being the seminal study for the application of the new treatment technique to this class of tumours. A more recent study [12] assessed the positive role of RA in the case of soft-tissue sarcoma in the legs with the possibility of significantly sparing the femurs.…”