Breast cancer with low FDG uptake: characterization by means of dual-time point FDG-PET/CT

Malignant breast lesions usually are differentiated by FDG-PET with a semiquantitative FDG standardized uptake value (SUV) of 2.5. However, the frequency of breast cancer with an SUV of less than or equal to 2.5 is noteworthy, and often present diagnostic challenges. This study was undertaken to evaluate the accuracy of dual-time point FDG-PET/CT with FDG standardized uptake value (SUV) calculation in the characterization of such breast tumors.

Forty-nine female patients with newly diagnosed breast cancer were found to have primary breast cancer with minimally increased FDG uptake and met the criteria for inclusion in this study by having borderline levels of increased FDG uptake (SUV max less than or equal to 2.5) in the initial FDG-PET/CT images. Consequently, they underwent further delayed phase FDG-PET/CT scan for better evaluation of the disease.

Of the 49 cancer lesions; the majority were found to have rising or unvarying dual-time changes in SUV max (75.5%). The median value of SUV max increases by 25% between the early and delayed scan. The means+/-S.D. of the SUV max1, the SUV max2, and the Delta SUV max% were 1.2+/-0.6%, 1.3+/-0.9%, and 5.1+/-22.4%, respectively. The receiver-operating-characteristic (ROC) analysis proved that the highest accuracy for characterization of malignant breast lesions was obtained when a Delta SUV max% cut-off value 0.0% was used as criteria for malignant FDG uptake-change over time with sensitivity 75.5%, and false-positive rate 20.4%.

These results suggested that dual-time FDG-PET/CT imaging with standardized uptake value (SUV) estimation can improve the accuracy of the test in the evaluation of breast cancer with low FDG uptake.