11.30 PDT Wednesday: I'm off to LA X this afternoon to catch the red eye back to London, which means this is the last Main Event post from the LA Convention Center. I'll wrap up the show blog when I get back to the office with a selection of the best physics papers from the scientific sessions and a review of some of the most innovative new products featured at the exhibition.
October 2007 Archives
09.30 PDT Wednesday: I went along to a couple of neat product demonstrations in the exhibition hall yesterday. First up, David Brett of BrainLAB, the German IGRT vendor, took me for a test drive on the company's iPlan RT treatment-planning software - specifically, iPlan RT Automatic Prostate Segmentation.
Traditional treatment-planning methods require a manual analysis of multiple CT scans of the prostate and surrounding organs, a process which is labour-intensive, time-consuming and often prone to questionable reproducibility. The iPlan software features a granular anatomical atlas which, when used as a template, can visualize each patient's internal dimensions through a process called "elastic fusion".
According to Brett, the BrainLAB software offers two big advantages versus standard manual contouring procedures. First, the time saved in critical steps, such as contouring tumours for accurate treatment outlines, enables more patients to be treated in a given timeframe. Second, the software enables clinicians to visualize risk structures with a much higher degree of consistency.
"The automatic segmentation tool can greatly enhance the overall efficiency of the contouring process [and] this leads to a reduction in the time required for contouring from an average of 30 minutes to five minutes per patient," explains a clinical validation note from Charles Enke and colleagues in the department of radiation oncology at the University of Nebraska Medical Center (Omaha, NE).
Brett says more than 120 hospitals worldwide have purchased iPlan RT Automatic Segmentation software since it was originally launched at the ASTRO annual meeting in 2005.
Next I met with the folks at Xoft, the Fremont, CA manufacturer which is pioneering a miniaturized electronic brachytherapy technology. Xoft's Axxent System is based around a 2.25 mm diameter X-ray source that delivers localized and targeted radiation treatment.
Unlike radionuclide-based brachytherapy sources, the radiation can be switched on and off as required. The lower energies involved remove the need for expensive shielding, while the lack of radioactive material eliminates the complex logistics associated with handling isotopes. As a result, Axxent is easier to deploy from a clinical perspective versus conventional approaches, giving doctors and patients better access to brachytherapy treatments.
Axxent's first commercial application is accelerated partial-breast irradiation (APBI), for which Xoft received 510(k) clearance from the US FDA in December 2005. Currently, there are 10 clinical sites using the system in post-clearance to treat early-stage breast cancer.
"We've also got 510(k) pending for our next clinical indication - endometrial cancer - but I don't want to put a timeframe on it right now," noted Marga Ortigas-Wedekind, Xoft's vice-president of marketing and development.
In APBI, which was being showcased on the booth, the Axxent system provides a therapeutic dose of intracavity radiation directly to the tumour bed, following lumpectomy. The electronic brachytherapy source is tailored to mimic the penetration and dose-rate characteristics of 192Ir (the isotope generally used for high-dose-rate brachytherapy) within the targeted treatment area.
The source itself comprises a disposable, 2.25 mm X-ray tube, integrated into a flexible sheath (with a total assembly diameter of 5.4 mm) attached to a treatment control console (see photo). The assembly is placed into the treatment cavity within a disposable balloon applicator, which serves as a scaffolding or centring device for the radiation source.
In terms of system design, the emphasis is clearly on automation and ease of use, with barcodes and a barcode scanner streamlining the workflow management and an on/off capability to ensure radiation safety.
10.20 PDT Tuesday: The building-sized RapidArc ad across from the LA Convention Center makes it clear where the big marketing push lies at Varian Medical Systems (Palo Alto, CA) this week. "Don't take slow for an answer," says the catchline for RapidArc, a technology that Varian claims "will enable clinicians to program a Varian linear accelerator to deliver more precise forms of IMRT up to eight times faster than is possible with conventional or helical IMRT (tomotherapy)".
RapidArc exploits customized algorithms to deliver a complete IMRT treatment in a single rotation of the linac around the patient, a procedure also known as volumetric modulated arc therapy (VMAT). Modulation is achieved by delivering successive arcs. For each arc, the beam aperture (as defined by the multileaf collimator) changes with the gantry angle to match the shape of the tumour.
"At the moment, Varian does Dynamic Arc, which means the clinician can adjust the treatment field every two degrees using the multileaf collimator in the head of the treatment machine," Neil Madle, Varian's director of investor relations, Europe, told medicalphysicsweb. "Doing this, you look at the tumour from every angle and you shape the field to the tumour. Now, we have devised a way of combining this with 3D imaging to do VMAT."
In this way, says Varian, it is possible to outstrip more time-consuming IMRT treatment methods, which require machines to make several rotations around the patient or to make repeated stops and starts to set up beam angles. According to the press release, "by varying three parameters simultaneously - the speed of rotation, the beam-shaping aperture and the dose delivery rate - doctors can create finely shaped IMRT dose distributions that more closely match the size and shape of the tumour while sparing healthy tissues."
In a conference call with medicalphysicsweb before the ASTRO meeting, Dow Wilson, president of Varian's oncology systems business, explained to me the commercial and clinical thinking behind RapidArc: "This is where we are with RapidArc radiation therapy. What we'd like to do is in two minutes set the patient up, know exactly where the tumour is and be ready in an image-guided fashion to deliver dose to that tumour. And then in the next two minutes, we'd like to complete the delivery of the prescription and get the patient off the table."
He continued: "Depending on where you are today, I'd say most IMRT is [delivered] in around a 10-20 minute cycle - 10 minutes on some of the simple treatments; 20 minutes, maybe even longer for some of the more complex treatments. The other thing that we're seeing [with RapidArc] is a substantial reduction in dose to critical [non-tumour] tissues. Conformality is terrific."
Dave Mellenberg, a technical leader at Varian, put it another way: "We're taking advantage of a number of unique features of our C-arm linac. It's like we had this Porsche and we were running it on city streets; now we're running it on the track at full throttle."
Varian is aiming to make RapidArc available for radiation clinics in spring 2008. The product is pending FDA 510(k) clearance and is not yet available for sale.
08.30 PDT Tuesday: At 11am yesterday, upwards of 200 delegates gathered around the Accuray booth to find out what the Sunnyvale, CA manufacturer had been keeping under wraps since the ASTRO trade show opened its doors Sunday (see "Getting it together", 28 October). A slick opening pitch from president and CEO Euan Thomson gave way to a swirling soundtrack from British supergroup Coldplay (a dubious choice in this correspondent's opinion) and then up went the curtain to reveal the 2008 model of the CyberKnife Robotic Radiosurgery System. The only thing missing was the dry ice, but a neat bit of theatre all the same.
For those who don't know, the CyberKnife is a radiotherapy system developed primarily for radiosurgery applications and comprised of a compact linac incorporated into an ultraprecise, computer-driven robotic arm (sub-mm accuracy). Patients lie on a couch while the robot positions the linac around them, an arrangement that permits the delivery of many fields from a range of source positions and angles, with robotic arm trajectories and beam weighting optimized iteratively by dedicated software. On-the-fly image guidance technology automatically detects and corrects for tumour and patient movement, adjusting the robot trajectory in real-time throughout treatment.
Innovation being what it is, however, the 2008 model of the CyberKnife incorporates a range of enhanced functionality. Thomson highlighted four specific advances:
• the Iris variable aperture collimator, which can automatically alter the size of its opening to let radiation beams of 12 discrete sizes pass through;
• an 800 MU/min linac that's capable of delivering higher dose rates to a tumour, in turn reducing treatment times;
• the Sequential Optimization Planning Tool, which will be integrated into the MultiPlan Treatment Planning System to enable users "to optimize their treatment objectives based on each unique clinical situation using prioritized clinical objectives, instead of the traditional trial-and-error setting of various constraints to narrow in on an optimized treatment";
• the RoboCouch patient positioning system with a seated load feature that offers "easier loading and unloading capabilities and provides added comfort for wheelchair bound or disabled patients".
Watch out for a more detailed update on Accuray's CyberKnife technology on the main pages of medicalphysicsweb next week.
15.15 PDT Monday: A couple of leading-edge cancer studies stood out from the background noise here today and mapped perfectly against the conference theme of "treating cancer while preserving quality of life". First up, the use of 4D CT to standardize the reporting of radiation dose volumes can lead to a more accurate radiation dose to the lungs when treating lung cancers - lowering the risk of lung injury in the process. That's the conclusion of a paper presented at the plenary session this afternoon by Yixiu Kang, a radiation physicist at M D Anderson Cancer Center in Houston, TX.
Basically, 4D CT allows clinicians to measure how much a tumour moves when a patient breathes - and in turn to compensate for this motion. Trouble is, radiation doses are measured by the volume of a person's lungs and lung volumes change during each phase of the breathing cycle. As a result, there is a substantial difference in the reporting of the amount of normal lung tissue exposed to radiation during treatment.
Kang and colleagues therefore set out to a) investigate various lung-volume definitions and their inter-relationships; b) evaluate the impact on lung dose-volume histograms (DVHs); and c) propose a population-based model for converting one lung-volume definition to another for prospective or retrospective dose reporting.
The authors believe theirs is the first study to evaluate the degree of differences that 4D CT has on dose volumes and to propose a method to standardize them for more effective radiation treatment. "We believe standardized reporting can lead to better interpretation of existing data and more accurate reporting of future studies," noted lead author Kara Bucci, a radiation oncologist at M D Anderson. "This will lead to improved risk assessment in planning individualized patient care."
The retrospective study involved 40 stage III/IV non-small-cell lung-cancer patients who received a 4D CT and a fast, free-breathing helical CT scan. The authors conclude: "We found large variations in reported DVH values when different lung-volume definitions were used. However, population-based relationships among different lung volumes can be used to convert DVHs into a more standardized dose-volume definition."
Next up at the plenary session, Rene-Olivier Mirimanoff, a radiation oncologist at the Centre Hospitalier Universitaire Vaudois in Lausanne, Switzerland, answered his own question - "Is long-term survival in glioblastoma possible?" - in the affirmative.
In fact, Mirimanoff went on to explain that more than four times as many patients with a rapidly fatal type of brain cancer, glioblastoma multiforme (GBM), who are treated with a combination of the chemotherapy drug temozolomide (TMZ) and radiation therapy can live for four years after diagnosis, compared to those who receive only radiation treatment.
Previously, GBM patients typically only lived between six to 12 months after diagnosis, and there were almost no survivors beyond two years. This type of cancer accounts for 20-25% of all primary brain tumours.
Early results of the Phase III trial published in the New England Journal of Medicine in 2005 showed for the first time that twice as many GBM patients who were treated with TMZ and radiation therapy survived two years after diagnosis, compared to those who received radiation alone. The trial involved 573 patients who were randomized to receive TMZ during and after radiation therapy or radiation alone. The combination treatment immediately became the standard treatment for GBM patients worldwide.
Subsequently, the researchers extended the study to find out if patients with GBM who had this treatment plan could live more than two years. The latest results, presented today, show that 12.9% of patients who added TMZ during and after radiation treatment lived for four years compared to 3.8% of those who received radiation alone and survived the same amount of time.
Findings also show that the main group of patients who survived for four years after diagnosis was less than 50 years old and in otherwise good health without any prior major medical condition. Over one-quarter (28%) of these patients who were treated with TMZ and radiation lived for four years, versus only 7% of patients who received only radiation therapy.
The researchers conclude: "The survival advantage conferred by the addition of TMZ to RT in GBM remains highly significant with a longer follow-up, and we expect a modest but significant proportion of patients to be long-term survivors."
Further reading
Y Kang et al. 2007 Which lung volumes to use for radiotherapy planning of lung cancer: inspiration, expiration, averaged, or free-breathing? Proc. 49th Annual ASTRO Meeting: Int. J. Radiat. Oncol. Biol. Phys. 69 3 S1.
R Mirimanoff et al. 2007 Is long-term survival in glioblastoma possible? Updated results of the EORTC/NCIC Phase III randomized trial on radiotherapy and concomitant and adjuvant temozolomide (TMZ). Proc. 49th Annual ASTRO Meeting: Int. J. Radiat. Oncol. Biol. Phys. 69 3 S2.
16.05 PDT Sunday: Joined-up thinking on IMRT is the headline theme of a study carried out at the University of Pittsburgh School of Medicine, PA. The results, which are being presented as a poster at the ASTRO meeting this week, demonstrate that IMRT for head-and-neck cancer can be uniformly delivered across a large healthcare network of academic and community cancer clinics with the help of a centralized planning and treatment process.
"Our study demonstrates that it is feasible for head-and-neck cancer patients to receive IMRT in their own communities without sacrificing high-quality care," said Dwight Heron, associate professor of radiation oncology, University of Pittsburgh School of Medicine and director of radiation oncology, University of Pittsburgh Medical Center. "This is possible through an integrated network in which treatment is standardized across all cancer centres."
IMRT treatment planning for the centres was performed at one main location, D3 Radiation Planning, located in Pittsburgh. With the help of telemedicine capabilities, however, medical physicists based at D3 were able to collaborate with radiation oncologists at community locations to develop individualized treatment plans for the patients.
According to the study results, there were no significant differences in toxicity profiles and treatment outcomes in 604 head-and-neck cancer patients treated with IMRT at 12 community cancer centres and one flagship academic facility.
The results show that 248 patients (41%) were treated at the flagship facility, and 356 patients (59%) received IMRT at one of the community centres. All 13 centres, connected through a telemedicine network, followed the same clinical pathway guidelines for the radiotherapy management of head-and-neck cancer, which included specific details on volumes for radiation treatment planning and recommended doses of IMRT.
When the investigators compared outcomes between the academic centre and the community centres, they found that there were no significant differences between survival or recurrence rates.
"By standardizing planning and treatment for IMRT, patients who live in remote locations can benefit from the same quality of care available at a large National Cancer Institute-designated comprehensive cancer centre," said Heron. "Bringing advanced radiation therapy to community locations can have a very positive effect on a patient's quality of life by relieving the anxiety and stress of travelling for treatment."
Further reading
A K Bhatnagar et al. 2007 Outcomes analysis of IMRT for treatment of head and neck cancers in a large NCI-designated integrated cancer center network Proc. 49th Annual ASTRO Meeting: Int. J. Radiat. Oncol. Biol. Phys. 69 3 S552.
14.53 PDT Sunday: The ASTRO meeting trade exhibition opened its doors this morning with a tuneful fanfare courtesy of the University of Southern California's marching band - the acoustics of the registration hall ensuring that the horn section was able to deliver an amplified wake-up call to red-eyed delegates (your correspondent included) with that fuzzy, jetlagged feeling.
A few hours in and Sunday's headline theme out on the show floor looks to be vendor partnership. First out of the blocks were IBA, the Belgian specialist in particle-therapy systems, and Elekta, the Swedish radiotherapy equipment maker.
The two companies announced a tie-up called the Global Particle Therapy Programme, which aims "to optimize the seamless integration of proton-therapy delivery and information management systems within the radiation oncology environment".
On the Elekta side, this can include an array of Elekta products such as the MOSAIQ workflow management and information system, MOSAIQ proton-therapy module, patient immobilization devices, localization systems, as well as the Elekta Synergy IMRT and IGRT delivery system. On the IBA side, the agreement includes the Proteus proton-therapy system, with the option to add more products in the future depending on customer requirements. Significantly, as well as joint development work, the two companies announced joint sales and marketing activities in this area.
Another one getting with the programme, so to speak, is CMS, the St Louis, MO-based vendor of treatment-planning and workflow-management products. Under the terms of its agreement with IBA, CMS has committed to provide particle-therapy solutions for a range of clinical requirements. This will include XiO, a treatment-planning platform for photon, electron and proton therapy; the Focal line of distributed planning workstations; and the CMS Direct suite of planning infrastructure and workflow-management products.
Not to be outdone, one of IBA's rivals in the proton-therapy market, Optivus Proton Therapy (San Bernardino, CA), announced a collaboration of its own: a joint venture with Parsons Commercial Technology Group, a division of Parsons Corporation, to build turnkey proton-therapy centres.
Founded in 1944, Parsons bills itself as "one of the largest, 100% employee-owned management, engineering and construction companies in the US". Optivus, for its part, was founded by the engineers who designed and installed the world's first hospital-based proton-therapy centre, at Loma Linda University Medical Center (Loma Linda, CA) in October 1990.
Also this morning, Varian Medical Systems (Palo Alto, CA) and Envisioneering Medical Technologies (St Louis, MO) announced that they are partnering to improve low-dose-rate (LDR) brachytherapy prostate-cancer treatments. Envisioneering is to configure its TargetScan, a prostate-cancer diagnostic and treatment system featuring 3D ultrasound and a stationary probe, to work with Varian's VariSeed brachytherapy treatment-planning software.
Ted Jackson, Varian's chief developer of the VariSeed software, claimed: "We can now automatically transport 3D prostate ultrasound images into our VariSeed system to plan and assess where seeds are placed and know with certainty how effectively the gland was treated. This represents the next evolution in prostate cancer treatment delivery and planning."
TargetScan's 3D imaging capability is designed to help physicians more effectively gather the gland's dimensions to calculate and monitor seed implantation. Its fixed probe "eliminates the time and costs associated with traditional systems and their digital stepper technology, which physically moves the ultrasound probe within the patient".
I'll be posting more reports from the exhibition throughout the week, including the low-down on Rapid Arc, Varian's big launch here at ASTRO. I'll also be revealing what's behind the big blue curtain on the Accuray booth. I did ask earlier but they said that if they told me they'd have to kill me; the big unveiling is scheduled for 11 a.m. tomorrow.
18.15 PDT Saturday: The Main Event, medicalphysicsweb's conference blog, cranks back into action tomorrow with daily reports from the 49th annual meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO) here in Los Angeles, CA.
The theme of this year's meeting, "Treating cancer while preserving quality of life", embraces all aspects of oncology care, with the emphasis on interdisciplinary collaboration between oncologists, physicists, biologists, nurses and other healthcare professionals.
Whether you're attending the meeting or not, The Main Event will endeavour to keep you in touch with the headline news from the conference sessions, as well as the pick of the new products and technology innovations featured at the trade exhibition. Enjoy the blog.
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