6. IN THE ZONE: USING LOW OXYGEN ZONES OF TUMORS TO GUIDE RADIATION THERAPY FOR HEAD AND NECK CANCERS
A familiar problem in cancer radiation therapy is the persistence of tumors that do not respond to standard doses. Tumors that are low in oxygen ("hypoxic") are in this category. They resist the curative effects of both radiation and chemotherapy-but that may change as a result of preliminary work by a group of New York researchers.
While much research is devoted to molecular manipulations to reverse or block the hypoxic tumor-promoting environment, the New York team is taking a new tactic: They are using the low-oxygen chemical signal to guide an adjustable-strength radiation treatment called Intensity Modulated Radiation Therapy (IMRT). The intensity modulation approach not only uses the low-oxygen environment to locate zones of radiation resistance, it then delivers extra radiation doses to the zones in hopes of overcoming resistance to standard doses. Researchers can also scale back the dose to minimize damage to tissues characterized by normal oxygen levels.
N. Lee, M.D. (firstname.lastname@example.org), from Memorial Sloan-Kettering Cancer Center in New York, is the lead researcher. She explains the significance of the team's work this way: "Our results are able to visualize variable levels of hypoxia within tumors, which is potentially important for future therapies because it suggests this is a feasible approach to locating pockets of resistance and gaining local control over head and neck cancers."
Dr. Lee's group tested this approach in 10 patients with head and neck cancer. To visualize the tumors' oxygen environments they radioactively labeled tracers and gave them intravenously to patients. The tracers were detected and displayed as an image by a technology known as 18F-fluoromisonidazole positron emission tomography (PET) scanning. Low oxygen zones were revealed based on a tumor zone's uptake of the tracers. Regions of elevated 18F-fluoromisonidazole were identified as low in oxygen, and then treated with an intensity-modulated radiation boost to overcome the resistant zones.
Talk (WE-D-AUD C-2), "Hypoxia-Guided Intensity-Modulated Radiation Therapy for Head and Neck Cancer" is at 1:30 p.m. on Wednesday, July 30, 2008 in Auditorium C. Abstract: http://www.aapm.org/meetings/amos2/pdf/35-9784-92744-669.pdf.****************************************************************
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