18F–FDG-PET/CT for systemic staging of patients with newly diagnosed ER-positive and HER2-positive breast cancer

Abstract

Objectives: This study assesses 18F–FDG-PET/CT for patients with newly diagnosed estrogen receptor-positive/human epidermal growth factor receptor-negative (ER+/HER2-) and human epidermal growth factor receptor-positive (HER2+) breast cancer. Methods: In this Institutional Review Board-approved retrospective study, our Healthcare Information System was screened for patients with ER+/HER2- and HER2+ breast cancer who underwent 18F–FDG-PET/CT prior to systemic or radiation therapy. The initial stage was determined from mammography, ultrasound, magnetic resonance imaging, and/or surgery.18F–FDG-PET/CT was evaluated to identify unsuspected extra-axillary regional nodal and distant metastases. The proportion of patients upstaged overall and stratified by stage and receptor phenotypes was calculated along with confidence intervals (CI). Results: A total of 238 patients with ER+/HER2- and 245 patients with HER2+ who met inclusion criteria were evaluated. For patients with ER+/HER2-breast cancer, 18F–FDG-PET/CT revealed unsuspected distant metastases in 3/71 (4%) initial stage IIA, 13/95 (14%) stage IIB, and 15/57 (26%) stage III. For patients with HER2+ breast cancer, 18F–FDG-PET/CT revealed unsuspected distant metastases in 3/72 (4%) initial stage IIA, 13/93 (14%) stage IIB, and 13/59 (22%) stage III. The overall upstaging rate for IIB was 14% (95% confidence interval (CI): 9–20%). Conclusions: 18F–FDG-PET/CT revealed distant metastases in 14% (95% CI: 9–20%) of patients with stage IIB ER+/HER2- and HER2+ breast cancer, which is similar to upstaging rates previously seen in patients with stage IIB triple-negative breast cancer (15%, 95% CI: 9–24%). The detection of unsuspected distant metastases in these patients alters treatment and prognosis. NCCN guidelines should consider adding patients with stage IIB breast cancer for consideration of systemic staging with 18F–FDG-PET/CT at the time of initial diagnosis.