Novel heterogeneity method for predicting survival in non-metastatic triple-negative breast cancer

This study aimed to investigate the relationship between semiquantitative positron emission tomography (PET) parameters and intratumoral heterogeneity (ITH) on ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) imaging and survival data of non-metastatic triple-negative breast cancer (TNBC) patients.

Sixty-two consecutive female patients who underwent pretreatment ¹⁸F-FDG PET/CT with non-metastatic TNBC were enrolled. Heterogeneity index (HI) variables derived from the metabolic tumor volume (MTV) and standardized uptake value (SUV) parameters of primary lesions were evaluated. A novel modified method introducing a percentage-based (30-40-50%) MTV slope comparison was proposed. The association between conventional ¹⁸F-FDG PET/CT parameters, HI values, and survival results was analyzed retrospectively.

Tumors with higher HI values were associated with shorter survival times. For overall survival (OS), HI2 and HI3 were statistically significant (p=0.009, p=0.016). Regarding radiological progression-free survival (rPFS), HI1 and HI3 were statistically significant (p=0.01, p=0.025). A significant weak correlation between HI1 (p=0.005, ρ=0.34) and a strong correlation was found for HI2 (p<0.0001, ρ=0.89), HI3 and tumor size were not statistically significantly correlated (p=0.063, ρ=0.23). T stage was statistically significantly associated with rPFS and OS ((p=0.038, p=0.003). In contrast, no statistically significant difference was found for the N stage, anatomical, and clinical staging (p>0.05).

This study concluded that ITH predicts survival for non-metastatic TNBC patients. This conclusion was reached with the heterogeneity index variables obtained by different methods. However, our results revealed that HI2 depends on tumor size. Our modified method (HI3) predicts survival independently of tumor size.