Baseline F-FDG PET/CT for predicting pathological response to neoadjuvant chemotherapy and prognosis in locally advanced breast cancer patients: analysis of tumor and lymphoid organs metabolic parameters.

Purpose: To investigate metabolic parameters from baseline F-FDG PET/CT as predictors of pathological complete response (pCR) to neoadjuvant chemotherapy (NAC) and disease recurrence in locally advanced breast cancer (LABC) patients.

Materials And Methods: From 142 LABC in 137 patients (bilateral-synchronous BC: 5/137), the following parameters from baseline (pre-treatment) F-FDG PET/CT were retrospectively analyzed, along with clinic-histological data: primary tumor activity (SUVmax, SUVmean, SUVpeak, tumor-to-liver ratio-TLR-, MTV, TLG); lymphoid organs activity (spleen and bone marrow SUVmax and SUVmean, spleen-to-liver ratio-SLR-, bone marrow-to-liver ratio-BLR); and PET-positive lymph-nodes' number. Predictors of pCR and recurrence-free survival (RFS) were assessed by univariable logistic regression and Cox regression (significant or suggestive association: p < 0.05; p < 0.10).

Results: 74/142 tumors were "Luminal A/B HER2-", 44/142 "Luminal B HER2+/HER2+", 24/142 TNBC; pCR after NAC occurred in 26/142 tumors (18.3%) and disease recurrence at follow-up (45 ± 18.1 months) in 25/127 assessable patients (19.7%). Significant or suggestive predictors of NAC response, in Luminal A/B HER2-: lower spleen SUVmax and patients' age (OR 0.06; 0.93) for pCR; lower TLRmax, TLRmean and BLRmax (OR 1.33; 1.22; and 26.42) for residual disease. Significant negative RFS predictors: higher SUVmax, SUVmean, SUVpeak (HR 1.10; 1.15; 1.11), TLRmax and TLRmean (HR 1.02; 1.00), MTV and TLG (HR 1.32; 1.26) in Luminal A/B HER2-; higher spleen SUVmax, PET-positive nodes' number and patients' age (HR 6.24; 1.20; 1.08) in Luminal B HER2+/HER2+.

Conclusion: Primary tumor and lymphoid organs parameters at baseline F-FDG PET/CT resulted as predictors of NAC response and prognosis in LABC patients, respectively, reflecting the BC cells' proliferative activity and metabolic burden, and the role of tumor-induced immune-system activation on tumors' behavior and treatment responsiveness. In LABC candidates to NAC, baseline PET information could improve treatment planning and prognostic stratification.