Axillary lymph node metastases detection with nuclear medicine approaches in patients with newly diagnosed breast cancer: Can positron emission tomography (PET) with F-18-FDG be considered as the best method?

Three different tracers, Tc-99m-Sesta MIBI, In-111-Pentetreotide and F-18-FDG, were evaluated in a preliminary study in three different groups of 10 breast cancer patients programmed for breast cancer resection and axillary dissection. Planar scintigraphy and single photon emission tomography (SPET) technique were used for imaging with Tc-99m-Sesta-MIBI and In-111-Pentetreotide, positron emission tomography (PET) was used for imaging with F-18-FDG. We studied 30 breast cancer patients; their clinical stage according to the TNM classification was 30 T1-T2, 1 T4 and 1 Tx (one patient had bilateral cancer and one had bifocal cancer). The lymph nodal status ranged from NO to N2 (14 NO, 16 N1, 1 N2). Tc-99m-Sesta MIBI, In-111 Pentetreotide SPET and F-18-FDG PET were randomly performed before surgery to visualize the primary tumors and to detect axillary lymph node invasion. Tc-99m-Sesta MIBI correctly visualized 10 out of 11 primary cancers in 10 patients. In-111-Pentetreotide detected 9 out of 10 primary cancers. F-18-FDG imaged all the tumors (10). As regards the axillary nodes, Tc-99m-MIBI excluded axilla involvement in 7 out of 7 negative axillae (N-), while it was positive in 2 out of 3 positive cases (N+); In-111-Pentetreotide correctly identified 7 out of 8 negative axillae (N-), while it detected 2 of 3 positive sites. F-18-FDG visualized all positive axillary lymph nodes (4 out of 4 N+ patients) and correctly excluded involvement in all negative patients (6 out of 6 N- cases). This study demonstrated that all three tracers are adequate to be proposed as tumor seeking agents with the aim of developing non-invasive diagnostic methods for pre-operative detection of axillary metastases, so that surgical dissection can be limited to selected patients. The authors discuss the advantages and disadvantages of the different radiopharmaceuticals and conclude that in centers with PET facilities F-18-FDG is the best tumor seeking agent for the evaluation of axillary status. Between Tc-99m-Sesta MIBI and In-111-Pentetreotide the former seems to present more advantages in this kind of application, considering also its lower cost and easier availability. These results encourage further study, including the simultaneous comparison of these tracers in breast cancer staging.