Volumetric Intensity-Modulated Arc Therapy Vs. Conventional IMRT in Head-and-Neck Cancer: A Comparative Planning and Dosimetric Study

The purpose of this study was to investigate the potential benefits of using triple‐arc volumetric‐intensity modulated arc radiotherapy (RapidArc (RA)) for the treatment of early‐stage nasopharyngeal carcinoma (NPC). A comprehensive evaluation was performed including plan quality, integral doses, and peripheral doses. Twenty cases of stage I or II NPC were selected for this study. Nine‐field sliding window IMRT, double‐arc, and triple‐arc RA treatment plans were compared with respect to target coverage, dose conformity, critical organ sparing, and integral doses. Measurement of peripheral doses was performed using thermoluminescent dosimeters in an anthropomorphic phantom. While similar conformity and target coverage were achieved by the three types of plans, triple‐arc RA produced better sparing of parotid glands and spinal cord than double‐arc RA or IMRT. Double‐arc RA plans produced slightly inferior parotid sparing and dose homogeneity than the other two delivery methods. The monitor units (MU) required for triple‐arc were about 50% less than those of IMRT plans, while there was no significant difference in the required MUs between triple‐arc and double‐arc RA plans. The peripheral dose in triple‐arc RA was found to be 50% less compared to IMRT near abdominal and pelvic region. Triple‐arc RA improves both the plan quality and treatment efficiency compared with IMRT for the treatment of early stage NPC. It has become the preferred choice of treatment delivery method for early stage NPC at our center.PACS numbers: 87.53.Bn, 87.55.D, 87.55.de, 87.55.dk, 87.56.ng

Section: Discussionmentioning

confidence: 99%

A comprehensive dosimetric evaluation of using RapidArc volumetric‐modulated arc therapy for the treatment of early‐stage nasopharyngeal carcinoma

Kan

Wong²,

Leung³

et al. 2012

“…With the availability of automated gantry and couch movements, the treatment efficiency possibly could be further enhanced to an extent where this technique potentially can be used as a standard for HNC IMRT. The total beam on time with MI4 π ‐VMAT appears to be similar to that of conventional SF‐IMRT for HNC, which also ranges from 8–12 min 3, 4…”

Section: Discussionmentioning

confidence: 77%

“…Since VMAT has shown improved treatment efficiency with lesser monitor units compared to SF‐IMRT, we have attempted a multi‐isocentric noncoplanar VMAT using approximately 880–1350 degrees of freedom 2, 3. Our approach fundamentally differs from theirs in terms of use of volumetric arcs (instead of vvSF‐IMRT) in noncoplanar workspace using multiple isocenters creating multiple spheres of dose clouds.…”

Section: Discussionmentioning

confidence: 99%

“…Since its introduction in 2008, volumetric‐modulated arc therapy (VMAT) has been extensively evaluated for treating HNC 2, 3, 4, 5, 6, 7, 8. The literature suggests that both treatment efficiency and sparing of organs at risk (OAR) are superior with VMAT compared to conventional static field IMRT (SF‐IMRT), although questioned by some authors 2, 3. Early clinical outcome reports showed comparable toxicity and local control with respect to IMRT 4, 5, 6.…”

Section: Introductionmentioning

confidence: 99%

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Multi‐isocentric 4π volumetric‐modulated arc therapy approach for head and neck cancer

Subramanian

Subramani

Chilukuri

et al. 2017

ObjectivesTo explore the feasibility of multi‐isocentric 4π volumetric‐modulated arc therapy (MI4π‐VMAT) for the complex targets of head and neck cancers.MethodsTwenty‐five previously treated patients of HNC underwent re‐planning to improve the dose distributions with either coplanar VMAT technique (CP‐VMAT) or noncoplanar MI4π‐VMAT plans. The latter, involving 3–6 noncoplanar arcs and 2–3 isocenters were re‐optimized using the same priorities and objectives. Dosimetric comparison on standard metrics from dose‐volume histograms was performed to appraise relative merits of the two techniques. Pretreatment quality assurance was performed with IMRT phantoms to assess deliverability and accuracy of the MI4π‐VMAT plans. The gamma agreement index (GAI) analysis with criteria of 3 mm distance to agreement (DTA) and 3% dose difference (DD) was applied.Results CP‐VMAT and MI4π‐VMAT plans achieved the same degree of coverage for all target volumes related to near‐to‐minimum and near‐to‐maximum doses. MI4π‐VΜΑΤ plans resulted in an improved sparing of organs at risk. The average mean dose reduction to the parotids, larynx, oral cavity, and pharyngeal muscles were 3 Gy, 4 Gy, 5 Gy, and 4.3 Gy, respectively. The average maximum dose reduction to the brain stem, spinal cord, and oral cavity was 6.0 Gy, 3.8 Gy, and 2.4 Gy. Pretreatment QA results showed that plans can be reliably delivered with mean gamma agreement index of 97.0 ± 1.1%.Conclusions MI4π‐VMAT plans allowed to decrease the dose‐volume‐metrics for relevant OAR and results are reliable from a dosimetric standpoint. Early clinical experience has begun and future studies will report treatment outcome.

“…The use of VMAT in head and neck treatments may offer a combination of reduced treatment time, better organ‐at‐risk (OAR) sparing, or increased target dose conformality compared to other treatment types 2 , 3 , 4 , 5 . Many head and neck treatment plans include regional lymph nodes in the supraclavicular area.…”

Section: Introductionmentioning

confidence: 99%

Effect of interfractional shoulder motion on low neck nodal targets for patients treated using volumetric‐modulated arc therapy (VMAT)

Casey

Wong

Tung

2015

VMAT is an important tool in the treatment of head and neck cancers, many of which also require treatment to the supraclavicular lymph nodes. However, full VMAT arcs treating this nodal region necessarily cause entrance beam to pass through patients' shoulders. Thus, interfractional variations in shoulder position may cause unwanted dose perturbations. To assess this possibility, six patients undergoing treatment at our institution for head and neck cancers with associated supraclavicular lymph node treatment were imaged with in‐room CT‐on‐rails during the course of their treatments. This allowed for the establishment of a true record of the actual shoulder position during selected treatment fractions. Then, a full VMAT plan and a plan with VMAT arcs superior to the shoulder and a static anteroposterior field inferiorly were copied onto the patients' weekly image sets. The average one‐dimensional shoulder motion was generally within 10 mm of the simulated position, with some notable exceptions. The standard deviation in week‐to‐week shoulder position relative to simulation was 4.3 mm and 4.2 mm in the SI and AP dimensions, respectively. The average nodal target mean dose across all fractions sampled was within 5% of planned for all patients and both plans. Similarly, the average D95 for the nodal target was within 5% of planned across all fractions sampled, with the single exception of the full VMAT plan for one patient. In most cases, the standard deviation in both target mean dose and D95 was smaller with the VMAT+static AP field plan than it was with the full VMAT plan.PACS number: 87.55.‐x