Risk stratification in patients with newly diagnosed stage III or IV breast cancer by metabolic parameters of primary tumor in ¹⁸F-FDG PET/CT

Objectives Total lesion glycolysis (TLG) is a derived parameter combining volumetric and metabolic information of tumors with increased uptake on ¹⁸F-FDG PET/CT. The aim of this study was to investigate whether pretreatment TLG of primary tumor provides additional prognostic value in stage III or IV breast cancer (BC) patients beyond standard clinico-pathological factors.

Methods Pretreatment PET/CT scans from 240 consecutive patients with newly diagnosed stage III or IV BC were retrospectively analyzed. Maximum standardized uptake value (SUV_max), metabolic tumor volume (MTV), and TLG of primary tumor and clinico-pathologic factors were compared. Univariate and multivariate analyses were performed to identify factors associated with progression-free survival (PFS) and BC-specific overall survival (OS).

Results TLG with a threshold of 30% (TLG_30%) outperformed SUV_max and volume-based metabolic parameters for predicting disease progression and death. Mean TLG_30% of primary tumors for stage III and IV patients were 405.14 g and 753.44 g, respectively. Optimal cutoff value of TLG_30% was 158 g. PFS rates at 5 years for stage III patients with TLG_30% ≤158 g versus TLG_30% >158 g were 82.2% and 65.7%, respectively. PFS rates for stage IV patients with TLG_30% ≤158 g versus TLG_30% >158 g were 40.0% and 8.8%, respectively. OS rates at 5 years for them were 86.4%, 68.0%, 57.4% and 14.1%, respectively. Patients with stage III BC and TLG_30% >158 g had similar OS rates as those with stage IV and TLG_30% ≤158 g (P = 0.359), especially for the first 3 years. Patient survival with stage IV disease and a primary tumor TLG_30% greater than 158 g remained worst.

Conclusions This is the first and largest series of patients reported to show that TLG_30% from pretreatment PET/CT images can effectively stratify both stage III and IV BC patients, may lead to better management of these high-mortality-risk patients.