Pretreatment 18F-FDG uptake heterogeneity predicts response to pyrotinib in patients with metastatic HER2-positive breast cancer.

Abstract

e15026 Background: Heterogeneity of 18F-fluorodeoxyglucose (FDG) uptake is a promising marker for predicting response to treatment. This study aimed to evaluate the ability of pretreatment positron emission tomography/computed tomography (PET/CT) 18F-FDG-based heterogeneity to predict the response to pyrotinib in patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC). Methods: Patients with MBC in the Fudan University Shanghai Cancer Center who underwent whole-body 18F-FDG PET/CT before the initiation of pyrotinib was included. The intertumoral and intratumoral heterogeneity indexes (HI-inter and HI-intra, respectively), maximum standardized uptake value (SUVmax), total lesion glycolysis (TLG), and metabolic tumor volume (MTV) on the baseline PET/CT were assessed. Progression-free survival (PFS) was estimated by the Kaplan-Meier method and compared by log-rank test. Time-dependent receiver operating characteristic (ROC) curve analysis was performed, and the predictive accuracies of all markers were evaluated by plotting the cumulative area under the ROC curve (AUC) over time. Results: A total of 22 patients were included in this study. The median PFS of patients with a high HI-intra (> 1.9) was 6.6 months, whereas that of patients with a low HI-intra was 13.4 months (p = 0.044). The HI-inter was able to discriminate patients as well as the coefficient of variance. Univariate analysis showed that patients with a higher HI-inter tended to have worse PFS (10.6 months vs. 13.4 months, p = 0.067). Higher SUVmax and TLG were also associated with worse PFS. ROC curve analysis confirmed the predictive value of the HI-inter and HI-intra. TLG had the highest accuracy in predicting PFS (AUC = 0.87), followed by HI-inter (AUC = 0.86), SUVmax (AUC = 0.85), HI-intra (AUC = 0.80), mean standardized uptake value (AUC = 0.63), and MTV (AUC = 0.60). Conclusions: Intratumoral and intertumoral heterogeneities in metastatic lesions on pretreatment 18F-FDG PET/CT could predict response to pyrotinib treatment in patients with HER2-positive breast cancer, which could provide information to guide treatment decisions.