Metabolic characterization of inflammatory breast cancer (IBC) with baseline FDG-PET/CT: Relationship with histopathology, hormone receptor status, and pathologic response after neoadjuvant chemotherapy.

Abstract

1105 Background: Higher metabolic activity on FDG-PET is associated with triple negative (TN) hormone receptor status and invasive ductal histopathology in non-IBC breast cancer. Pts with IBC and a complete pathologic response (pCR) in mastectomy tissue after neoadjuvant chemotherapy (NAC) have a better prognosis compared to pts with residual disease. The objectives were to characterize IBC on baseline FDG-PET with respect to hormone receptor status, tumor grade and to determine if baseline metabolic activity in primary or metastatic lymph nodes (LN) predicts pCR. Methods: This is an IRB-approved retrospective study of 28 pts. SUVmax of primary IBC tumor and local LN metastases were compared between (b/w) pts with pCR versus residual disease, b/w pts with different receptor status (ER, PR, HER2), and b/w pts with different grade tumors (1-3). Results: Baseline SUVmax was higher in 6 pts with TN tumors (median 12.4, range 5.4-29.3) compared with 22 pts with ER+ or PR+ or HER2+ tumors (5.0, 2.0-16.3, p=0.04). SUVmax in local LN metastases tended to be higher in TN tumors vs. others (11.2, 2.7-27.9 vs. 5.4, 2.0-15.5, p=0.06). SUVmax in primary IBC was not different based on tumor grade (p=0.26), but higher SUVmax was seen in metastatic LN in pts with grade 3 vs. 2 tumors (10.5, 2.0-27.9 vs. 4.7, 2.0-10.2, p=0.02). SUVmax of primary IBC tumor was not significantly different b/w pts with pCR (median 10.6, range 2-29.3) vs. residual disease (6.4, 2.5-13.6, p=0.36). No significant difference was seen b/w baseline SUVmax of locally metastatic LN between pts with pCR (9.0, 3.3-27.9) vs. residual disease (6.1, 2.0-16.2, p=0.13). Conclusions: Baseline metabolic activity of primary IBC tumor and locally metastatic LN did not predict pCR at mastectomy. Triple-negative receptor status is associated with higher SUVmax in primary tumor and marginally in metastatic LN suggesting a more aggressive nature. These findings are consistent with data in non-IBC breast cancer.