Although ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) has demonstrated utility in predicting short-term and mid-term recurrence of breast cancer, its association with long-term prognosis in estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer remains unclear. This study aimed to evaluate whether tumor FDG accumulation on pretreatment ¹⁸F-FDG PET/CT predicts long-term recurrence-free survival (RFS) and overall survival (OS) in ER-positive, HER2-negative early-stage breast cancer and to investigate factors associated with early and late recurrence.

This retrospective study analyzed 332 patients with ER-positive, HER2-negative early-stage breast cancer treated between 2008 and 2010. Univariable and prespecified parsimonious multivariable Cox proportional hazards regression analyses were performed to assess factors associated with RFS and OS, with tumor maximum standardized uptake value (SUV_max) analyzed as a continuous variable. Patients were stratified into early recurrence (within 5 years) and late recurrence (over 5 years) groups for analysis.

In total, 332 patients (56 ± 13 years; all women) were included. During a median follow-up of 121 months, 33 patients (9.9%) experienced recurrence and 13 patients (3.9%) died. In multivariable analyses for RFS, tumor SUV_max was independently associated with outcome in the clinical stage-based model (hazard ratio [HR], 1.48; 95% confidence interval [CI], 1.34–1.63; P < 0.01). In the Ki-67–adjusted sensitivity model, tumor SUV_max (HR, 1.49; 95% CI, 1.36–1.63; P < 0.01) and high Ki-67 expression (≥ 20%) (HR, 2.46; 95% CI, 1.14–5.31; P = 0.02) were independently associated with RFS. For OS, tumor SUV_max was the only variable independently associated with outcome in multivariable analyses (HR, 1.40; 95% CI, 1.22–1.61; P < 0.01). In subgroup analyses, early recurrence was associated with tumor SUV_max and high Ki-67 expression in univariable analyses. For late recurrence, multivariable analysis showed that older age (HR, 1.04; 95% CI, 1.01–1.07; P = 0.01) and tumor SUV_max (HR, 1.50; 95% CI, 1.35–1.68; P < 0.01) were independently associated with recurrence.

Pretreatment tumor SUV_max on ¹⁸F-FDG PET/CT was associated with long-term RFS and OS in patients with ER-positive, HER2-negative early-stage breast cancer. SUV_max may have potential prognostic value that requires independent validation, while clinicopathological factors associated with recurrence differed between early and late recurrence.