Asphericity of FDG uptake on ¹⁸F FDG PET/CT provides independent prognostic value in breast cancer patients with lymph node metastasis.

Objectives The purpose of this study was to evaluate the prognostic implication of ‘asphericity’ (ASP); spatial irregularity; of FDG uptake in the primary tumor on pretherapeutic ¹⁸F-FDG PET/CT scans in patients with invasive ductal carcinoma (IDC) of the breast.

Methods Sixty seven female IDC patients(mean age=49.3±11.6) with pathologically confirmed lymph node metastasis and more than 2cm of tumor size were retrospectively evaluated. SUV2.5 was taken as the cut-off value for the detection of tumor boundaries. ASP was calculated using following formula to characterize the deviation of the tumor’s shape from sphere symmetry (Ψ = A_s/A_p = π^1/3(6V_p )^2/3/A_p,see supplement). Clinicopathologic factors and metabolic PET parameters (maximum standardized uptake value [SUVmax], metabolic tumor volume [MTV], and total lesion glycolysis [TLG]) were measured. Univariate and multivariate analyses for the progression free survival (PFS) were performed with these factors and parameters.

Results The PFS rate among the 67 patients was 82.1%. The mean follow-up times was 47.6months. The ASP ranged from 3.44 to 72.48 (mean, 22.35 ± 15.81). T stage, N stage, hormonal receptor(ER/PR) status, SUVmax (≤ 5.5), MTV (≤ 4.2 cm3), TLG (≤ 15.1), and ASP (≤ 13.1) affected the PFS on univariate analysis. In multivariate Cox regression, ASP (HR=10.9), and hormonal receptor status (HR=9.1) were independent prognostic factor for PFS.

Conclusions ASP on ¹⁸F-FDG PET/CT is an independent predictor of outcome in IDC patients, and could improve their prognostic stratification.