The program was moderated by Dr. John M. Hoffman, head of the National Cancer Institute's molecular imaging program. The NCI has shown extraordinary interest in PET for monitoring the effects of cancer therapies. The motivation for this new movement stems from the transition from cytotoxic to cytostatic cancer therapies, according to Dr. Anthony Shields, a professor of medicine and oncology at Wayne State University. Cytotoxic agents induce physiological responses, such as primary tumor shrinkage, that can be measured with anatomically based imaging modalities. In some cases, these physiological changes do not appear for months after the start of chemotherapy or radiation therapy.
Cytostatic therapies inhibit cellular signaling or interfere with cancer cell growth.
Although tumors do not appear to change physiologically, profound metabolic changes can be measured, using PET, within days after the administration of a therapeutic agent. A poor response can be identified quickly, so a potentially more effective alternative can be prescribed. Metabolic imaging has huge implications for oncology. Cancer is increasingly being viewed as a chronic disease, along the lines of AIDS and diabetes. These changes require more than a simple shift from CT imaging to PET, said Dr. Steven Larson, chief of nuclear medicine at Memorial Sloan-Kettering Cancer Center.