Detection ability of preoperative F-18 FDG PET/CT for axillary nodal metastasis in stage T1 and T2 breast cancer

Objectives The value of FDG PET/CT for axillary nodal staging in overall breast cancer has been relatively well established. However, reports on FDG PET/CT in axillary nodal staging in early stage of breast cancer are still lacking. We aimed to evaluate the ability of FDG PET/CT for the preoperative diagnosis of axillary nodal metastasis in T1 and T2 stage breast cancer.

Methods We enrolled 46 patients (51.7±11.4 y/o) with stage T1 and T2 breast cancer who underwent preoperative PET/CT and surgery. Based on surgical and histologic results, we estimated the efficacy (sensitivity[SN], specificity[SP], positive predictive value[PPV], negative predictive value[NPV] and accuracy[AC]) of PET, CT and PET/CT, respectively, to detect axillary nodal metastasis.

Results Of the 46 patients, 31 were stage T1 and 15 were stage T2. One hundred-one nodes proved to be positive for metastasis. The mean size and pSUV of all metastatic nodes were 7.5±3.2 mm (95% confidence interval[CI]; 6.6-8.5 mm) and 5.7±4.5 (95% CI; 4.4-7), respectively. There was a significant correlation between the pSUV of metastatic nodes and size of them (r = 0.814, p = 0.001). The respective SN, SP, PPV, NPV and AC were 40.6% (41 of 101), 67.7% (21 of 31), 87.3% (41 of 51), 25.9% (21 of 81) and 47.0% (62 of 132) in CT, 47.5% (48 of 101), 76.7% (23 of 30), 87.3% (48 of 55), 30.3% (23 of 76) and 54.2% (71 of 131) in PET and 48.5% (49 of 101), 67.7% (21 of 31), 83.1% (49 of 59), 28.8% (21 of 73) and 53.8% (70 of 132) in PET/CT. When 1.4 of pSUV was added as diagnostic criteria of PET/CT to differentiate benign from metastasis, the ROC curve showed the maximal SN (92.0%), SP (66.7%) and AC (89.1%).

Conclusions This study showed FDG PET/CT had a limitation in detecting axillary nodal metastasis in stage T1 and T2 breast cancer. This study also indicated that metabolic activity by PET is more important factor than morphologic characteristics by CT to discriminate benign node from metastatic node