18F-FDG PET-Derived Volume-Based Parameters To Predict Dis-Ease-Free Survival in Patients With Grade III Breast Cancer of Different Molecular Subtypes Candidates to Neoadjuvant Chem-Otherapy

Aim: This study aimed to investigate whether baseline 18F-FDG PET-derived semiquantitative parameters could predict disease-free survival in patients with grade III breast cancer of different molecular subtypes undergoing neoadjuvant chemotherapy (NAC). Materials and Methods: Patients were retrospectively retrieved from the databases of two Italian hospitals (University of Padua and University Hospital of Ferrara). Inclusion criteria were: 1) histologically proven diagnosis of grade III breast cancer; 2) history of NAC; 3) execution of a baseline 18F-FDG PET/CT scan before the start of NAC; 4) adequate follow-up time to compute the 3Y-DFS. For each 18F-FDG-PET/CT scan, the following parameters were calculated in the primary tumor (SUVmax, SUVmean, MTV, TLG) and whole-body (WB_SUVmax, WB_MTV, and WB_TLG). Receiver operating characteristic (ROC) analysis was used for each parameter to assess the prediction capability for 3Y-DFS. DFS differences between groups were assessed using Kaplan-Meier curves and compared by log-rank test. Results: Ninety-five grade III breast cancer patients with different molecular types were retrieved (luminal A: 5; luminal B: 34; luminal B-HER2: 22; HER2-enriched: 7; triple-negative: 27). In the whole group of patients, WB_SUVmax was the best predictor of recurrence (AUC: 0.66; best cut-off: WB_SUVmax>9.43; SS: 96%; SP: 38.1%; p<0.008). Patients with luminal A and Her-2-enriched breast cancer types were excluded from the molecular subgroup analysis due to the small study samples (5 and 7, respectively). In luminal B patients (n=34), WB_MTV (AUC: 0.75; best cut-off: WB_MTV>195.33; SS: 55.56%, SP: 100%; p=0.002) and WB_TLG (AUC: 0.73; best cut-off: WB_TLG>1066.21; SS: 55.56%, SP: 100%; p=0.05) were the best predictors of 3Y-DFS. Patients had a higher probability of DFS in case of a WB_MTV≤195.33 (3429±210 vs. 446±144 days; p<0.001) or WB_TLG≤ 1066.33 (937.35±19 vs. 496±131 days; p<0.001). In luminal B-HER2 patients (n=22), WB_SUVmax was the only predictor of 3Y-DFS (AUC: 0.857; best cut-off: WB_SUVmax>13.12; SS: 100%; SP: 71.43%; p<0.001); patients with WB_SUVmax≤13.12 had a significantly longer DFS (3857 days) than patients with a WB_SUVmax >13.12 (1693±430 days; p<0.004). No parameter resulted significant in the prediction of 3Y-DFS in patients with grade III triple-negative cancer. Conclusion: Volume-based parameters, extracted from baseline 18F-FDG PET, seem to be promising tools in the prediction of recurrence within 3 years in patients with grade III luminal B and luminal B- HER2 breast cancer undergoing NAC. Larger study samples are needed to confirm these preliminary findings.