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CANCER RESEARCH HIGHLIGHTS
From the 50th AAPM Meeting in Houston, July 27 to July 31

7. STUDY CORRELATES TEMPORAL CHANGES IN TUMOR HETEROGENEITY TO TREATMENT RESPONSE

Tumors are notoriously heterogeneous. Although the cells of a tumor may descend from the same progenitor cell, they can mutate to become genetically unique, displaying distinct characteristics and behavior, and responding differently to environmental assaults. Some cancer cells, for example, may be highly resistant to radiation therapy, while others are insensitive to the drugs used in chemotherapy, all of which can confound cancer therapy. But does tumor heterogeneity change because of cancer treatment?

Chihwa Song (csong1@wisc.edu), a postdoctoral researcher in the Department of Medical Physics at the University of Wisconsin, Madison, has with his colleagues taken the first steps toward finding an answer. The scientists conducted a statistical analysis of heterogeneity and its progression in nine people undergoing radiotherapy and six people getting chemotherapy, for various types of cancer. Each patient underwent diagnostic imaging prior to, and during, treatment.

Using a special type of positron emission tomography scan, the researchers looked for variation within tumors in the rates at which clumps of cells proliferate, which could be visualized as clusters of rapidly growing cells. A rapid rate of cell proliferation is one characteristic of highly malignant tumors. Song and colleagues found no major changes in proliferation heterogeneity over the course of radiotherapy treatment, but a large decrease in the amount of heterogeneity during chemotherapy. A larger decrease in heterogeneity could mean that the patients were becoming more responsive to their treatment.

The study, Song says, "seems to show that tumor heterogeneity changes over the time course of treatment, with response to treatment related to that change," although the reasons why remain unclear. "If this is true, a change in tumor heterogeneity will serve as a prognostic tool."

Talk (TH-D-AUD C-05), "Assessment of Heterogeneity Change in Tumors over Time Course of Treatment" is at 1:18 p.m. on Thursday July 31, 2008 in Auditorium C. Abstract: http://www.aapm.org/meetings/amos2/pdf/35-9117-60820-214.pdf.

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ABOUT AAPM

The American Association of Physicists in Medicine (AAPM) is a scientific, educational, and professional nonprofit organization whose mission is to advance the application of physics to the diagnosis and treatment of human disease. The association encourages innovative research and development, helps disseminate scientific and technical information, fosters the education and professional development of medical physicists, and promotes the highest quality medical services for patients. In 2008, AAPM will celebrate its 50th year of serving patients, physicians, and physicists. Please visit the association's Web site at http://www.aapm.org/.

ABOUT AIP

Headquartered in College Park, MD., the American Institute of Physics is a not-for-profit membership corporation chartered in New York State in 1931 for the purpose of promoting the advancement and diffusion of the knowledge of physics and its application to human welfare.

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