RESUMO
Objective:To evaluate the value of pretreatment 18F-fluorodeoxyglucose (FDG) PET/CT-based heterogeneity for early prediction of targeted therapy outcome in patients with human epidermal growth factor receptor 2 (HER2) positive metastatic breast cancer. Methods:From May 2012 to April 2018, 29 patients (all females, median age: 52 (32-69) years) who had HER2 positive metastatic breast cancer and underwent pretreatment 18F-FDG PET/CT in Fudan University Shanghai Cancer Center were retrospectively enrolled. All patients received trastuzumab as first-line treatment and were followed up for 6-87 (median time: 35) months. The relations between clinicopathologic parameters or PET/CT-based parameters and progression-free survival (PFS)/overall survival (OS) were analyzed with Cox univariate analysis. The parameters with P≤0.01 were further analyzed with Cox multivariate analysis. Optimal cut-off values were determined by time-dependent receiver operating characteristic (ROC) curve analysis. The survival analyses were estimated by Kaplan-Meier method and log-rank test. Results:The median OS of the 29 patients was 30 (6-83) months, and the median PFS was 10 (2-29) months. The PET/CT-based heterogeneity index(HI), including the maximum standardized uptake value (SUV max) ratio (SUV max-R; hazard ratio ( HR)=8.6, 95% CI: 2.7-27.8, P<0.001), the mean standardized uptake value (SUV mean)-2.5 (the cut-off value of standardized uptake value (SUV)=2.5) ratio (SUV mean-2.5-R; HR=2.6, 95% CI: 1.2-5.9, P=0.020), the metabolic tumor volume(MTV)-2.5 ratio(MTV-2.5-R; HR=2.4, 95% CI: 1.1-5.2, P=0.030), and the total lesion glycolysis(TLG)-2.5 ratio(TLG-2.5-R; HR=3.2, 95% CI: 1.4-7.4, P=0.008) of the lesion with the highest SUV max to that with the lowest SUV max, were significantly associated with PFS. None of the parameters was significantly associated with OS (all P>0.05). Multivariate analysis showed that the SUV max-R was the only independent predictor for PFS ( HR=6.8, 95% CI: 1.8-26.1, P<0.01). Area under the ROC curve for SUV max-R was 0.747. With a cut-off value of 1.8, SUV max-R could effectively distinguish the benefit from non-benefit population treated with trastuzumab (15.0 vs 7.0 months; χ2=18.68, P<0.01). Conclusion:Pretreatment 18F-FDG PET/CT-based HI has potential value for early prediction of first-line trastuzumab treatment outcome in patients with HER2 positive metastatic breast cancer.
