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The Use of RapidArc™ in the Treatment of Prostate Cancer
and Antonella Richetti
1. Head, Research in Medical Physics; 2. Head, Medical Physics Service; 3. Consultant; 4. Head, Department of Radiation Oncology,
Oncology Institute of Southern Switzerland
RapidArc™ is a radiation therapy planning and delivery approach based on a volumetric intensity-modulated arc technique that has recently
been introduced into clinical practice for a variety of cancer types. RapidArc is based on the theory that fast volumetric treatments with
modulated arcs can significantly improve the quality of delivery of radiation doses, with a direct influence on conformal avoidance of treatments
(reduction of toxicity and increase of local control). The Oncology Institute of southern Switzerland pioneered this technique, and men with
prostate cancer represent the largest group treated to date. Although the preliminary clinical results are based on a short follow-up, the findings
are encouraging. Single-arc plans are delivered in time slots of 10 minutes, thus increasing clinical capability; comparison with standard
alternative techniques provided superior dosimetric results, and image guidance during treatment has been implemented as a mandatory
quality assurance procedure.
Prostate cancer, RapidArc™, intensity-modulated volumetric arc therapy, image-guided radiation therapy
Disclosure: Luca Cozzi is a Scientific Advisor to Varian Medical Systems AG, Zug, Switzerland. The remaining authors have no conflicts of interest to declare.
Received: 9 June 2009 Accepted: 11 July 2009
Correspondence: Luca Cozzi, IOSI, Medical Physics Unit, Oncology Institute of Southern Switzerland, 6504 Bellinzona, Switzerland. E: firstname.lastname@example.org
A Novel Technology and prescription ranged from 70Gy (20Gy for boost with RapidArc only) to
Its Role in Radiation Oncology 78Gy in 2Gy fractions, i.e. no acceleration or hypofractionation
RapidArc™ is a radiation therapy planning and treatment approach schemes have been implemented until now. Target mass included
based on a volumetric intensity-modulated single arc that falls into either the prostate alone or was expanded to include the seminal
the more general category of intensity modulation therapy (IMRT) with vesicles and lymphatic stations. The total number of fractions delivered
arcs. It is based on an original investigation by Otto.
Among the with RapidArc ranged from 10 (boost only) to 39 (entire treatment).
pioneers in the late 1990s, Yu’s group clarified the benefit of using
multiple, coplanar or non-coplanar modulated arcs for most complex All patients were treated with daily fractions using a photon beam of
The research group at UZ Gent in Belgium applied multiple 6MV nominal energy generated by a linear accelerator (Clinac
non-coplanar modulated arcs to pelvic treatments (rectum and whole Varian Medical Systems) equipped with an MLC (Millennium™ MLC-
proving that intensity-modulated arcs 120) and a radio-transparent treatment couch. All patients were
offered equivalent or superior target coverage and highly improved treated with a single-arc approach. Each arc was delivered in 74±1
sparing of organs at risk compared with conventional treatments. seconds, with a total number of monitor units (MU) ranging from 291
RapidArc aims to achieve several objectives at once: improve OARs to 655, corresponding to 0.7–1.8MU per degree of beam rotation.
and healthy tissue sparing compared with other IMRT solutions; Preliminary dosimetric data suggest that the treatment was delivered
maintain or improve the same degree of target coverage; and with a very high degree of conformal avoidance, i.e. with the
significantly reduce the treatment time (beam on time) per fraction. capability of properly irradiating the prostatic target mass while
simultaneously minimising irradiation of organs at risk, primarily the
At the current stage of implementation, RapidArc allows for bladder and rectum.
optimisation of single or multiple, coplanar or non-coplanar arcs with
single or multiple isocentre selection. With RapidArc, intensity Figure 1 shows the dose distribution that can be achieved in a typical
modulation is achieved by means of concomitant optimisation of patient with a RapidArc plan in axial, coronal and sagittal views. A
multileaf collimator (MLC) shapes, dose rate and gantry speed. statistical summary of the 3D dose distribution provided by the dose–
volume histogram is provided in Figure 2. Here the red line corresponds
Potential of RapidArc for Prostate Cancer to the target mass, brown and yellow lines represent the rectum and
Between its clinical introduction in September 2008 and May 2009, bladder, respectively, and the remaining lines refer to the femoral heads.
about 110 patients were treated with RapidArc at the Oncology
Institute of Southern Switzerland (IOSI). Of these, 50 patients As a summary of the main parameters, Table 1 provides a direct
weretreated at IOSI for prostatic carcinoma, in various stages. Dose comparison between RapidArc treatments and the planning
24 © TOUCH BRIEFINGS 2009