The Main Event
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ASTRO intro
16.49 Sunday ET: The 48th annual meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO) kicked off in earnest today at the Pennsylvania Convention Center here in Philadelphia. For those of you who aren’t familiar with ASTRO’s annual meeting, the official literature describes it as “a forum where oncologists, medical physicists, biologists, nurses and other health professionals involved in radiation therapy come together to present and discuss the latest advances in cancer diagnosis and treatment”. Thanks to a handily colocated trade exhibition, the assembled masses also have an opportunity to get to grips with the latest technologies and products from equipment makers large and small.
The organizers were talking it up from the off - like all good show organizers, they already have one eye on the 2007 annual meeting (in Los Angeles). Fair enough, really, given that they’re predicting a record attendance for this week’s meeting, somewhere around 11,000 delegates. The other indicators look pretty healthy too: 1200+ conference papers, an abstracts book that runs to more than 800 pages (and weighs in at 5 lb or thereabouts), and a sold-out trade show with 200+ exhibiting organizations.
Bottom line: it’s going to be a busy week and there’s going to be a lot of talking about a lot of stuff - and a lot of writing to be done on all that stuff. Clearly, time for your correspondent to indulge in some fierce prioritization. So rule number one this week is easy enough: it’s better to do a few things well, rather than a lot of things badly. Rule number two is don’t forget rule number one. For you the readers, this means that medicalphysicsweb’s ASTRO blog won’t guarantee to give you all the news as it happens. What it will give you, with a trailing wind, is some of the more newsworthy developments pretty soon after they’re announced, and backed up with informed comment and opinion direct from the conference sessions and the exhibitors’ booths. Down to business then…
Particle physics
Let’s start in the exhibition hall - busy for a Sunday - and two product announcements that caught the eye. We’ve posted a couple of stories about particle therapy on medicalphysicsweb in the past week, and here’s another notable move in this area. IBA of Belgium announced today the commercial launch of its COMPACT Proton Therapy System, now cleared by the US Food & Drug Administration.
This a case of think smaller, think cheaper, with a scaled-down approach that’s set to reduce the amount of upfront capital expenditure needed on an entry-level proton-therapy centre. A large multiroom proton-beam facility typically comes in at well over $120 m. Now, though, IBA is claiming that its COMPACT PT system - including building, equipment and medical software - will be available “at less than one-fourth of the previously needed investment” (though the company concedes that the new format will not have the throughput capacity of larger centres).
IBA reckons that while a larger proton-therapy centre is justified for a region with 10 million people, the COMPACT PT system will be a “perfect solution” to cover geographic areas serving 1 to 5 million people.
The proposed layout of the new system brings the gantry as close as possible to the cyclotron, reducing the length of the beam-transport system so as to achieve minimal building footprint. The cyclotron and the gantry cannot be brought any closer because energy selection should take place in the cyclotron vault, so that no neutrons coming from the process can reach the patient.
Meanwhile, proton-beam therapy also features in the latest contract win for UK imaging specialist Vision RT. The company reports encouraging uptake of its AlignRT product in the US since it received 510(k) clearance earlier this year. The latest sale is to Massachusetts General Hospital (MGH) in Boston, which is to install the system in its proton-therapy department. This comes in addition to the two AlignRT systems already in use in conventional linear accelerators at MGH’s main radiotherapy clinic.
Essentially, AlignRT is a stereoscopic optical system for tracking the 3D surface of the patient for both patient set-up and real-time monitoring in 3D image-guided radiation therapy. George Chen, director of the radiation physics division at MGH, plans to use AlignRT to study variations in surface topology and their impact on charged-particle therapy. “Consider the following example: a female patient is treated for lung cancer with a heavy charged-particle beam,” he explained in a press statement. “Variations in breast position from day to day may result in changes in beam penetration. If the change in radiological depth to the tumour is as small as about 3 mm, this may result in approximately 1 cm geometric overshoot. Other sites where surface monitoring may be of value include head and neck and pelvis.”
Home-town knowledge
As you’d expect, Philadelphia researchers and clinicians are well represented in this week’s conference programme. Today, a team from Fox Chase Cancer Center presented research showing that men undergoing prostate-cancer treatment have fewer long-term gastrointestinal side-effects with intensity-modulated radiation therapy (IMRT) than with 3D conformal radiation therapy (3D CRT) - despite the higher doses used on the IMRT patients.
The researchers analysed data collected prospectively from 1417 patients treated at Fox Chase. Of these, 928 men were treated with 3D CRT and 489 men with IMRT. Patients were matched for PSA level (prostate-specific antigen, measured by blood test and used to determine if prostate cancer is present), T-stage (palpable size) and Gleason score (tumour aggressiveness determined by pathologic testing).
The study evaluated gastrointestinal side-effects such as short-term diarrhoea and longer-term bowel dysfunction. It also considered genitourinary problems such as urinary frequency, urgency and, in a few cases, painful or difficult urination or obstructive symptoms.
“There were no differences in the reporting of acute gastrointestinal or genitourinary side-effects for the two treatment modalities,” explained Alexander Kirichenko, lead author of the study. “However, as the data are beginning to mature, we’re seeing more long-term gastrointestinal side-effects in the men treated with 3D CRT.”
Even though patients treated with IMRT had higher radiation doses, there were fewer gastrointestinal side-effects three years after treatment (6.3% for IMRT; 10.4% in 3D CRT). The research showed no statistically significant difference between the two treatment types for genitourinary side-effects.
Kirichenko, who’s now at Allegheny General Hospital (Pittsburgh, PA), added: “Despite the specific findings pertaining to the 3D CRT technique and the gastrointestinal side-effects, men treated with either modality have acceptable rates of side-effects at this point in our analysis, particularly when compared to data from surgical outcomes.”
More from the conference tomorrow, including news of the top three cancer-research papers as chosen by the conference committee.
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