Locally advanced breast cancer (LABC): 99mTc-MIBI mammoscintigraphy (MMS) and fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT)

Objectives To evaluate the evidences obtained from association of MMS and FDG PET/CT in LABC.

Methods We prospectively enrolled 42 LABC pts who underwent within 1 week both MMS and PET/CT. For MMS we calculated the tumor to background ratio (T/B) and the most intense uptake of T/B according to specific formulas. The percentage washout index (WO%) for T and I were made. Standardized uptake values (SUVs) were obtained by PET/CT. The imaging results were correlated with histological findings.

Results 24 and 18 pts were at stage II and III, respectively. 34 pts had an invasive ductal cancer. ki67 median value was 39.8. 14 pts were classified as triple negative (TN) and 28 as no-TN. A significant uptake of tracer in the primary T was showed at MMS and PET/CT. MMS showed a slightly higher detection rate for axillary lymph node (LN) than PET/CT (82 vs. 78%), while PET/CT recognized distant LNs and skeletal metastases in 13 pts. WO%T and WO%I median values were respectively 41.9 and 36.9%. SUVmax median value in primary T was 11. The WO%T was lower in TN than no-TN. Moreover, 6 TN and 18 no-TN had both WO%T and WO%I <45%. Similarly was reported for WO%T in negative and positive HER2 tumors.

Conclusions A difference related to WO%T was found between TN and no-TN pts and positive and negative HER2 subjects, although not statistically significant. Perhaps a slow WO%T from early to late MMS scan could be correlated with a major responsiveness to neoadjuvant treatment in aggressive BC.