Dual time point 18 F-fluorodeoxyglucose positron emission tomography/computed tomography fusion imaging ( 18 F-FDG PET/CT) in primary breast cancer.

Background: To evaluate the clinicopathological and prognostic significance of the percentage change between maximum standardized uptake value (SUV _max ) at 60 min (SUV _max 1) and SUV _max at 120 min (SUV _max 2) (ΔSUV _max %) using dual time point ¹⁸ F-fluorodeoxyglucose emission tomography/computed tomography ( ¹⁸ F-FDG PET/CT) in breast cancer.
Methods: Four hundred and sixty-four patients with primary breast cancer underwent ¹⁸ F-FDG PET/CT for preoperative staging. ΔSUV _max % was defined as (SUV _max 2 - SUV _max 1) / SUV _max 1 × 100. We explored the optimal cutoff value of SUV _max parameters (SUV _max 1 and ΔSUV _max %) referring to the event of relapse by using receiver operator characteristic curves. The clinicopathological and prognostic significances of the SUV _max 1 and ΔSUV _max % were analyzed by Cox's univariate and multivariate analyses.
Results: The optimal cutoff values of SUV _max 1 and ΔSUV _max % were 3.4 and 12.5, respectively. Relapse-free survival (RFS) curves were significantly different between high and low SUV _max 1 groups (P = 0.0003) and also between high and low ΔSUV _max % groups (P = 0.0151). In Cox multivariate analysis for RFS, SUV _max 1 was an independent prognostic factor (P = 0.0267) but ΔSUV _max % was not (P = 0.152). There was a weak correlation between SUV _max 1 and ΔSUV _max % (P < 0.0001, R ²  = 0.166). On combining SUV _max 1 and ΔSUV _max %, the subgroups of high SUV _max 1 and high ΔSUV _max % showed significantly worse prognosis than the other groups in terms of RFS (P = 0.0002).
Conclusion: Dual time point ¹⁸ F-FDG PET/CT evaluation can be a useful method for predicting relapse in patients with breast cancer. The combination of SUV _max 1 and ΔSUV _max % was able to identify subgroups with worse prognosis more accurately than SUV _max 1 alone.