The Effect of FDG-PET/CT on Clinical Prognostic Staging of Breast Cancer Patients being Planned Neoadjuvant Treatment.

Objective: To evaluate the effect of FDG-PET/CT in the radiological imaging of breast cancer (BC) patients planned for neoadjuvant treatment (NAT), on the clinical prognostic stage (CPS).

Study Design: A descriptive study.

Place And Duration Of Study: Haydarpasa Numune Training and Research Hospital, Istanbul, Turkey, between June 2014 and September 2020.

Methodology: Consecutive patients with stage I-III breast cancer (BC) who were planned for neoadjuvant treatment (NAT). The distribution of CPS detected by both conventional radiological methods (c-CPS) and FDG-PET/CT (PET-CPS) were compared.

Results: Significant upstaging on CPS was detected with the addition of FDG-PET/CT to conventional imaging methods in 25/121 (20.7%) patients (p <0.001). In the c-CPS stage, IB, IIA, IIB, IIIA, IIIB patients, the stage change rate was 22.7%, 28.6%, 37.5%, 50%, and 9.1%, respectively. There was no change in patients with c-CPS stage IA and IIIC. There was a significant change in the cN stages (p <0.001), while no significant change was detected in the cT stages of the patients (p = 0.180). Upstaging was detected in 5/16 (6.3%, p=0.034), 14/71 (19.7%, p <0.01), 15 / 30 (50%, p <0.01) of initially cN 0, 1, 2 patients, respectively (p<0.001).

Conclusion: The change in CPS was due to nodal upstaging. The effectiveness of including FDG-PET/CT in the initial radiological imaging in patients planned for NAT should be evaluated with prospective studies evaluating treatment choices to be used in NAT. Key Words: PET scan, Breast cancer, Positron emission tomography, Neoadjuvant treatment, Cancer staging, Staging system, TNM.