PET imaging can reassure previously treated women they are breast cancer free, and can better predict if their disease is likely to recur than other types of diagnostic imaging, according to a study published in The Journal of Nuclear Medicine.

A team of researchers from the University of California, Los Angeles compared the outcomes of 61 women previously treated for breast cancer. The women received both 18F-FDG PET and conventional imaging (CI), and were followed-up for at least 6 months to determine how, or if, their disease progressed.

Significantly, all six women with positive CI results, indicating their disease had returned, but whose PET scans were negative, were actually free of disease at their last follow-up. In the nine women with negative CI but positive PET results, six were later found to have recurrent disease and received additional treatment. Overall, PET and CI findings differed in a quarter of the women; PET correctly predicted the outcome in 80% of these cases vs. 20% for CI.

PET was also better at determining the length of disease-free survival, with 90% accuracy vs. 75% for CI. Women with positive results for both PET and CI showed similar periods of survival; however, women with negative PET results had significantly longer disease-free survival than those with negative CI results. Overall, PET demonstrated better sensitivity (93% v. 79%) and specificity (84% v. 68%) than CI. CI includes imaging techniques such as x-ray, CT, sonography, MRI, mammography, and bone scans.

The authors pointed out that early detection of local recurrence and metastatic disease can impact therapy. For example, local recurrence and axillary lymph node involvement may be treated surgically or with radiation, whereas mediastinal lymph node involvement or distant metastases typically require chemotherapy. The six women with true-positive PET results and false-negative CI were able to receive treatment for their recurrence, such as additional chemotherapy, radiation, and surgery. However, at the end of follow-up, all six women had evidence of disease. The authors concluded that although earlier detection did not result in remission in these cases, it might have delayed the progression of disease.

The Center for Medicare and Medicaid Services (CMS) decided on February 27 to reimburse for FDG PET scans for staging patients with distant metastasis or for restaging patients with locoregional recurrence or metastasis, and to determine how patients are responding to treatment.

SOURCES:
The Journal of Nuclear Medicine, March 2002; 43:325-329
Society of Nuclear Medicine (http://www.snm.org)