A Retrospective Study Comparing Immunohistochemistry Subtyping and Findings on F-18 FDG PET/CT in Patients with Invasive Breast Cancer

Abstract

INTRODUCTION: Breast cancer (BC) is a major global public health concern, and its diverse pathology makes management particularly complex. Molecular subtypes, identified through immunohistochemistry (IHC), along with metabolic activity and disease extent revealed by Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT), provide valuable insights. Exploring the relationship between IHC subtypes and F-18 FDG PET/CT findings can enhance personalized BC management.

AIM: The study aimed to assess the correlation between IHC subtypes and F-18 FDG PET/CT findings in patients with invasive BC referred for staging, restaging, and response assessment at the Charlotte Maxeke Johannesburg Academic Hospital (CMJAH) Nuclear Medicine department.

METHOD: A retrospective analysis was conducted on histologically confirmed invasive BC patients who underwent F-18 FDG PET/CT between January 2016 and September 2022 at CMJAH. Patient demographics, IHC markers (ER, PR, HER-2, Ki-67%) on the initial histology, patterns of disease spread and SUVmax values of tumours on PET/CT were collected and analysed.

RESULTS: This study included 136 BC patients. FDG PET/CT was predominantly indicated for restaging (71%), followed by response to therapy assessment (18%) and staging (11%), detecting disease in 102 (75%) cases. Although not statistically significant, bone metastases were prevalent in hormone receptor-positive subtypes, while triple negative breast cancer (TNBC) showed a predilection for lung metastases. Higher Ki67% and standardized uptake value maximum (SUVmax) values, a marker proliferation and tumour aggressiveness, were significantly associated with TNBC subtype with a mean Ki67% of 70% (range, 40-80%) and SUVmax of 13.5 (range, 7.2-19), while Luminal A tumours exhibited the lowest values with a mean Ki67% of 10% (range, 5-20%) and SUVmax of 6.8 (range, 4.3-11). P-values of 0.0001 for Ki67% and 0.0564 for SUVmax.

CONCLUSIONS: vi The study highlights a significant correlation between IHC markers and FDG PET/CT imaging, particularly regarding the Ki67% and SUVmax, across different BC subtypes. These findings underscore the utility of FDG PET/CT not only in evaluating the disease extent—spanning local, nodal, and distant metastases—but also in complementing IHC analysis for a more comprehensive diagnostic approach, offering valuable insights that can guide clinical decision-making for personalized patient care. Future studies should incorporate prospective designs and novel PET tracers to overcome our current limitations.