Abstract
492
Objectives: : FDG PET/CT is recommended in the staging of patients with high-risk breast cancer who will receive neoadjuvant chemotherapy or have a high probability of metastatic disease. Currently, usefulness of FDG PET/CT is uncertain for patients with clinically low-risk breast cancer, mainly due to its limited specificity. The purpose of this study was to investigate whether FDG PET can function as an independent biomarker in clinically low-risk breast cancer patients. Methods: Among 611 breast cancer patients who performed pre-operative FDG PET/CT from 2009 to 2016, 289 patients diagnosed with the TNM staging of I and IIa were retrospectively enrolled for this study. All patients were treated with surgery and adjuvant treatments, if applicable, according to the clinical practice guidelines. Recurrence was recorded during the follow-up, and progression free survival (PFS) was used as a primary endpoint for this study. Maximum standardized uptake value (SUVmax) of primary tumor was measured by FDG PET/CT. The TNM staging, hormonal status including estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), and a proliferation marker Ki67 were assessed using the surgical specimens. Further analysis was performed for the molecular subtypes of breast cancer; luminal A, luminal B, HER2, and triple negative breast cancer (TNBC) groups. Results: Recurrence was occurred in 19 patients during the follow-up (36.0 ± 23.5 months). PR was the most significant index to determine recurrence (P = 0.0115), along with Ki67 grade (P= 0.0403). In predicting PFS, SUVmax was the one of the significant indexes (P = 0.0054), and ER, PR and Ki67 were also significant (P = 0.0315, 0.0273 and 0.0055, respectively). The multivariate analysis revealed that SUVmax had a superior predictive power over PR (P = 0.0556 and 0.1278, respectively). The subgroup analysis came out to be significant only in the TNBC group. SUVmax was significant index (P < 0.0001) for recurrence, and SUVmax was the most significant index (P = 0.0007) in prediction of PFS of the TNBC group. Conclusions: FDG PET/CT can be useful as an independent imaging biomarker for predicting PFS in patients with clinically low-risk breast cancer. In particular, SUVmax can also be an effective quantitative index for prediction of PFS in TNBC subgroup. Although low-risk breast cancer tends to have favorable clinicopathologic features, FDG PET/CT can provide valuable information for further risk stratification.