FDG-PET/CT Protocol Stages Breast Cancer in One Session

The objective of a recent study was to compare the diagnostic accuracy of an all-in-one FDG-PET/CT whole-body and mammogram protocol to a multi-modality algorithm for initial breast cancer staging.

The study has concluded that whole-body FDG-PET/CT has a sensitivity in detecting primary breast cancer lesions similar to that for MRI mammography.

Participants/Methodology
Forty female patients (mean age, 58.3 years) with suspected malignancy on conventional mammograms underwent an FDG-PET/CT study. All patients also had undergone further staging with MRI mammography, ultrasound of the axilla, sentinel node lymphoscintigraphy and biopsy or surgery, bone scintigraphy, chest radiography, and ultrasound of the abdomen.

For each PET/CT study, each patient was intravenously injected with about 8 to 10 mCi (210 to 370 MBq) of the radiotracer (uptake period, 60 minutes). Whole-body PET was first performed from the head to the thighs, and then a second part was performed with the patient in the prone position using a breast-positioning aid (MammaComfort).

The second portion was at approximately 110 minutes (uptake period, two hours) and covered the axillary fossa to the lower end of the breasts.

A breast lesion was considered positive and suspicious for malignancy if it showed increased contrast enhancement compared to the surrounding breast tissue, as well as elevated FDG uptake.

Maximum standardized uptake values based on body weight were determined for each lesion. Clinical follow-up and histopathological findings were considered the standard of reference.

Results
The sensitivity of detecting primary breast cancers was similar for FDG-PET/CT versus MRI (95% and 100% respectively). T stage was more correctly identified by MRI (77%) than by PET/CT (54%). FDG-PET/CT detected axillary node involvement in 80% of cases, while clinical investigation and ultrasound did this in 70% (difference not statistically significant). Distant metastases were detected by multi-modality imaging in 70% of cases, and by FDG-PET/CT in 100% of cases. Management of patients was changed in 12.5% of cases based on FDG-PET/CT findings.

Conclusions
A single-session FDG-PET/CT mammography protocol can be used for staging breast cancer and appears to have similar accuracy to MRI. The exception is that MRI is more accurate for assessing the T stage.

Reviewer’s Comments
Other studies have shown that FDG uptake in primary breast cancer lesions can be much lower than that seen in metastatic lesions. This finding has been validated in my own personal experience. However, this has been with the utilization of whole-body imaging only. Apparently, the additional imaging reported in this study increases the sensitivity.

Author: Twyla Bartel, DO

Reference:
Heusner TA, Kuemmel S, et al. Breast Cancer Staging in a Single Session: Whole-Body PET/CT Mammography. J Nucl Med; 2008;49 (August): 1215-1222: