Associations between the standardized uptake value of ¹⁸F-FDG PET/CT and the prognostic factors of invasive lobular carcinoma: In comparison with invasive ductal carcinoma

The aims of this study were to evaluate the associations between the maximum standardized uptake value (SUVmax) and prognostic factors in invasive lobular carcinoma (ILC) and to compare these results with those in invasive ductal carcinoma (IDC). Methods: The study included pathologically confirmed ILCs (n=32) and IDCs (n=73). We retrospectively evaluated the preoperative ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) and measured the SUVmax. The pathologic results were reviewed regarding the size, histological type, histological grade, estrogen receptor (ER) and progesterone receptor (PR) status, human epidermal growth factor receptor 2 (HER2), epidermal growth factor receptor (EGFR), and Ki-67 of the primary tumor. We also compared the associations between the SUVmax and prognostic factors. Results: The mean SUVmax of the ILCs was significantly lower compared with that of the IDCs (P=0.032). The SUVmax increased with tumor grade (P<0.001) and was higher with ER negativity compared with ER positivity (P=0.007) in IDC. The SUVmax was higher with EGFR positivity compared with EGFR negativity (P=0.013) in IDC and higher with Ki-67 positivity compared with Ki-67 negativity in IDC and ILC (P<0.001 and P=0.002, respectively). The SUVmax was not significantly different regarding PR or HER2 for both tumor groups. The correlation between the tumor size and the SUVmax was demonstrated for IDCs (r=0.57), but not for ILCs (r=0.25). Conclusions: The SUVmax was significantly different according to the tumor grade, ER, EGFR, and Ki-67 for IDCs. The SUVmax exhibited a positive association with Ki-67 in ILC; however, it was not significantly different with other factors, which suggests that the role of ¹⁸F-FDG PET/CT may be limited in ILC.