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Studies on positron emission tomography (PET) using 18-F fluorodeoxyglucose (FDG) suggest that PET has an improved sensitivity and specificity for staging cancer patients compared with other imaging methods, such as CT scans. Research also suggests that PET may be useful in predicting response to treatment and detecting residual tumors. However, few studies demonstrated whether using PET leads to meaningful changes in treatment decisions or patient outcomes. A study supported in part by the Agency for Healthcare Research and Quality (HS13244) investigated the impact of PET on physician decisionmaking and found that physicians do often change their clinical decisions about management of cancer patients based on the results of PET scans.
Bruce E. Hillner, M.D., F.A.C.P., of Virginia Commonwealth University, and his colleagues studied the impact of PET on the clinical decisions of 71 physicians who were managing a group of patients undergoing PET at the university's medical center. The physicians completed a questionnaire before and after PET to obtain information regarding each physician's preceding actions, intended management of the patient, and probability estimates (for example, of metastatic disease).
Of the 248 patients, 40 percent had new or suspected cancer, and 60 percent were undergoing restaging (determination of whether the cancer is local, regional, or has metastasized to distant parts of the body) or had a suspected recurrence. Lung, lymphoma, and head/neck cancers accounted for two-thirds of cases. Following PET results, physicians changed their intended management in 61 percent of patients, and they retained the same management plan for 39 percent of patients.
In 32 percent of cases, physicians changed to a treatment from a nontreatment strategy. They changed the therapeutic goal (curative or palliative) and mode of treatment (for example, surgical resection, radiation, or chemotherapy) in 7 percent and 8 percent of cases, respectively. In about 25 percent of cases, patients who would have had additional testing or biopsy switched to treatment. Conversely, about 10 percent of patients went from additional testing or biopsy to watchful waiting.
The mean estimated probability of metastasis increased from 45 percent pre-PET to 58 percent post-PET. After PET, the physician summary impression was that 47 percent had more advanced disease, 41 percent had no change, and just 12 percent had less extensive disease than they thought before PET.
See "Clinical decisions associated with positron emission tomography in a prospective cohort of patients with suspected or known cancer at one United States center," by Dr. Hillner, Renuka Tunuguntla, M.B., and Melvin Fratkin, M.D., in the October 15, 2004, Journal of Clinical Oncology 22(20), pp. 4147-4156.
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