New proton therapy, breast CT clinical trials, radiation-resistant tumors

07/14/05

Press luncheon to showcase highlights of medical physics meeting

July 14, 2005--Lighting up radiation-resistant tumor regions, treating lung tumors with "4D" protons, and promising first images from an alternative to mammography are among the topics to be presented at a press luncheon for the 47th annual meeting of the American Association of Physicists in Medicine. Devoted to the scientific and professional tracks of the meeting, the press luncheon will take place on Tuesday, July 26, 2005 between 12 PM-1:30 in room 401 of the Washington State Convention & Trade Center, located at Pike Street and 7th Avenue. Members of the news media may contact Ben Stein at bstein@aip.org to attend the luncheon. Additional tips on the science program can be found at http://www.aapm.org/meetings/05AM/VirtualPressRoom/

The press luncheon will begin with an introduction to medical physics and the meeting by Howard Amols, the current president of AAPM, and the two scientific program co-directors, James Balter of the University of Michigan and Jeff Siewerdsen of the Ontario Cancer Institute in Toronto. Jerry White, the co-organizer of the meeting's professional track, is scheduled to describe professional sessions that cover topics of public policy interest, such as new procedures designed to reduce medical errors and ways to improve preparedness for radiological emergencies.

Then, four speakers who represent some of the world's top experts in medical physics will present scientific topics that contain some of the most newsworthy results at the meeting:

I . BREAST CT CLINICAL TRIALS
Speaker: John Boone, University of California, Davis, jmboone@ucdavis.edu
John Boone of UC-Davis will present some of the first images from human clinical trials of breast CT imaging, a potentially significant improvement over traditional mammography that aims to catch breast cancer earlier while eliminating patient discomfort. Traditional mammograms involve squeezing the breast between two plates and firing an x-ray that images the breast all at once. In breast CT, the patient lies down on a table and places one breast at a time through a circular opening, while a CT scanner produces 300 images per breast, in a period of just 17 seconds, to build up 3D images. According to Boone, the technique has the potential to catch tumors that are the size of a pea, as opposed to the garbanzo-sized tumors that can be caught with standard mammography, while not requiring painful breast compression. In addition, the 3D images can catch buried tumors that are ordinarily obscured by 2D mammograms. (Related Meeting Paper: SU-EE-A2-3, Sunday, 2:15 PM.)

II. IMAGE-GUIDED RADIATION THERAPY
Speaker: David Jaffray, Princess Margaret Hospital, Toronto, david.jaffray@rmp.uhn.on.ca
David Jaffray will review some of the latest developments in Image Guided Radiation Therapy (IGRT), a significant new technique that is springing up in cancer centers everywhere. IGRT combines two steps that were once separate in cancer therapy: obtaining good images of a tumor and delivering radiation to destroy it. IGRT makes it possible to obtain high-quality, real-time images during a cancer therapy procedure, so that professionals can aim radiation at the precise location of a tumor. This is a marked difference from the past, in which high-resolution images were obtained in separate machines prior to radiation treatment, making it very difficult to account for such factors as subtle shifts in tumors from day to day, or breathing that could move tumor location for moment to moment. The vast majority of work in Dr. Jaffray's laboratory focuses on the development of IGRT and other novel imaging concepts to improve the precision of therapy by generating images at the time of therapy for the purpose of guiding the treatment delivery. (Related Meeting Papers include: MO-E-J-6B-2, Monday, 4:25 PM.)

III. LIGHTING UP RADIATION-RESISTANT TUMOR REGIONS
Speaker: Andrei Pugachev, Memorial Sloan-Kettering Cancer Center, New York, pugachea@mskcc.org
Andrei Pugachev of the Memorial Sloan-Kettering Cancer Center will describe progress towards reliably finding and imaging regions of a tumor that are not destroyed by ordinary levels of radiation therapy. Fast-growing tumors often contain "hypoxic regions," or areas of lower-than-normal levels of oxygen, which turn out to be resistant to radiation. That's because when radiation damages DNA in a tumor cell, oxygen is needed to carry out additional chemical reactions to make the damage permanent. Currently, there are radioactive tracers that, when injected into the blood supply, will tend to bind to hypoxic regions in tissue and light them up for doctors to see in a PET scan. Pugachev and colleagues have devised a technique for verifying that PET tracers accurately map hypoxic regions. In animal studies of prostate tumors, they found that two specific PET tracers were reliable and one was not. By validating PET tracers in a two-step process (first, using animal tumor models and then patient tumor biopsies), researchers hope that they will soon be able to produce reliable, in-vivo images of these radiation-resistant tumor regions. (Related Meeting Paper: MO-D-I-609-8, Monday, 1:30 PM)

IV. PROTON THERAPY
Speaker: Hanne Kooy, Massachusetts General Hospital, Boston, hkooy@partners.org
In a small experimental patient study at Massachusetts General Hospital (MGH), researchers have increased the effectiveness of using protons to treat lung tumors. Treating cancer with protons, instead of traditionally used forms of radiation, offers advantages when it comes to avoiding damage in healthy tissue. Compared to x-rays and gamma rays, which penetrate deeply into the body, protons travel a more limited distance, and deposit most of their energy in a region known as the Bragg peak, the place where protons penetrate most deeply in tissue. In any radiation treatment of the lung, it is a challenge to keep the radiation on target while the tumor moves as a result of patient breathing. In the study at MGH, researchers have applied the 4D approach to proton therapy. In the 4D approach, one takes into account how the patient's breathing moves the lung back and forth over time (the fourth dimension) so that the radiation hits the tumor precisely over all phases of a patient's breathing cycle. In a study of four patients, they have found that planning and carrying out 4D proton therapy delivers excellent dose levels to lung tumors in all cases. After these initial promising results, the researchers plan to conduct expanded studies to investigate the usefulness of proton therapy for treating lung cancer. While only a few proton treatment centers currently exist in the U.S., the number of treatment centers is expected to grow exponentially in the coming years. (Related meeting paper: WE-E-J-6C-7, Wednesday, 4:42 PM)

Source: Eurekalert & others

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