103P PET-CT in localized breast cancer: Does it impact on the therapeutic decision?

The incidence of early breast cancer has increased since mammography screening. Accurate staging is essential to determine optimal treatment. Contrast enhanced mammography (Mx), Magnetic Resonance Imaging (MRI) and Ultrasound (US) are the gold standard for locoregional staging. Computed tomography (CT) staging is also indicated in high-risk cases. However, the increasing availability of PET-CT has challenged its use in early breast cancer. A search was conducted for patients with newly diagnosed operable breast cancer at Hospital Virgen del Rocío (Seville, Spain) from March 2017 to March 2023. Those who had PET-CT at diagnosis and after neoadjuvant treatment were selected and followed retrospectively We aimed to determine the concordance in staging between standard radiological assessment and PET-CT and its implications for therapeutic approach in our population. Also correlating PET-CT staging after neoadjuvant treatment and surgical staging in this group. 63 patients were identified. All were female. Median age was 51. Regarding tumor phenotype, 47 (74.6%) cases were luminal, 3 (4.8%) HER2 positive and 13 (20.6%) triple negative. By radiological techniques, 3.7% of patients were stage I, 32% stage IIA, 24.5% stage IIB, 20.7% stage IIIA, 7.5% stage IIIB, 11.3% stage IIIC and 1 (3.2%) patient stage IV In 54 patients with baseline US, PET-CT increased nodal staging from N1 to N2/N3 in 6 cases and decreased from N2 to N1 in 1 case. The correlation in staging between baseline radiologic techniques and PET-CT was 73.02% (k=0.61) for tumor size and 64.5% (k=0.42) for nodal assessment. Changes in PET-CT staging led to therapeutic modifications in 9 (14.3%) patients. Axillary staging correlated with PET-CT in 30 patients (90.9%) of the 33 patients who underwent post-neoadjuvant axillary US. 23 patients (33.3%) had a complete pathologic response in the surgical specimen. Of these, 19 patients had a complete response by PET-CT and 11 by standard evaluation. In our sample, PET-CT appears to increase sensitivity in preoperative staging, leading to a change in patient management in 14.3% of cases. It also shows a high correlation with surgical pathologic response.