Comparison of FDG PET and MRI for evaluating the tumor extent of breast cancer and the impact of FDG PET on the systemic staging and prognosis of patients who are candidates for breast-conserving therapy.

BACKGROUND: FDG PET has not yet found a role in the clinical evaluation of the tumor extent of breast cancer. FDG PET has been reported to be useful for evaluating the prognoses of breast cancer patients with more accuracy than conventional imaging modalities. The purpose of this study was to compare the accuracy of FDG PET and MRI for the preoperative assessment of the tumor extent of breast cancer, for evaluating the impact of FDG PET on systemic staging, and also for predicting the prognosis of patients who are candidates for breast-conserving therapy.

METHODS: The study was a prospective series of 23 breasts with breast cancer that underwent both FDG PET and MRI before surgery. Systemic staging with FDG PET was also performed. The correlation between the results of these examinations and histological findings was thus examined. The maximum standardized uptake value (SUVmax) of the tumors was investigated in association with the patient prognoses.

RESULTS: When evaluating the local tumor extent, the accuracy of FDG PET (43.5%) was significantly lower than that of MRI (91%) (P < 0.001). The sensitivity, specificity, and accuracy of FDG PET regarding the nodal status were 60, 94, and 87%, respectively. No patients demonstrated any distant metastasis, whereas FDG PET gave a false positive in one patient. The mean follow-up period was 61 months. The SUVmax value of the worse prognosis patient group was significantly higher than that of the good prognosis patient group (P = 0.032).

CONCLUSIONS: FDG PET is not a breast imaging modality for evaluating the local tumor extent, but it is useful for predicting the prognoses of patients who are candidates for breast-conserving therapy.