Initial Staging of Lobular Breast Carcinoma: Head to Head Comparison of 68Ga-FAPI-46 and 18F-FDG PET/CT (GALILEE)

Initial Staging of Lobular Breast Carcinoma: Head to Head Comparison of 68Ga-FAPI-46 and 18F-FDG PET/CT

Initial Staging of Lobular Breast Carcinoma: Head to Head Comparison of 68Ga-FAPI-46 and 18F-FDG PET/CT

Lobular Breast cancer staging with 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) is not optimal due to the poor accumulation of 18F-FDG in the tumour. Through better sensitivity (and specificity), 68Ga-FAPI-46-46 PET should provide a more accurate staging of lobular breast cancer than 18F-FDG PET.

Research hypothesis : Through better sensitivity (and specificity), 68Ga-FAPI-46-46 PET should provide a more accurate staging of lobular breast cancer than 18F-FDG PET. Participants with lobular breast carcinoma will then undergo 18F-FDG and 68Ga-FAPI-46 PET scan. Primary objective of the study is to compare the sensitivity of 68Ga-FAPI-46 with the sensitivity of 18F-FDG in the detection of lobular breast carcinoma lesions, measured by positron emission tomography (PET). These results will be compared with the histological data collected before or during surgery (conventional histological data and immunohistochemical labeling of FAPα on the sample obtained), clinical follow-up and any results of additional examinations carried out within the usual clinical follow-up of the patients. Comparison of primary tumor and metastases uptake of 68Ga-FAPI-46 with the uptake of 18F-FDG, radiomic study of 68Ga-FAPI-46 PET and comparative radiomic study of 68Ga-FAPI-46 PET and 18F-FDG PET and comparison of the specificity of 68Ga-FAPI-46 with the specificity of 18F-FDG after a 12-month follow-up will also be performed as secondary objectives.

68Ga-FAPI-46 is a radiotracer for the detection of Fibroblast Activation Protein (FAP) in cancer patients. 68Ga-FAPI-46 will be administered intravenously at a dose of 2MBq/kg. Patients will be scanned 60 minutes after administration of 68Ga-FAPI-46.

Number of positive tumor lesions, i.e. confirmed by additional imaging, histopathology/biopsy or response to treatment (on imaging or clinical assessment)

Comparison of 68Ga-FAPI-46 and 18F-FDG Standardized Uptake Value in the primary tumor and possible metastases

Comparison of (SUVmaxFAPI/reference) and (SUVmaxFDG/reference) activity ratios. For the primary tumour, the reference activity will be measured in either the periphery of the lesion or on a homologous healthy tissue. For a vertebral metastasis, the reference activity will be measured in an adjacent healthy vertebra.

Correlation between PET scans results and standard measurements in breast histology: OR (estrogen receptors), PR (progesterone receptors), HER2 (Human Epidermal Growth Factor Receptor-2), Ki-67 antigen, Ecadherin

1st order characteristics reflecting the distribution of gray levels determined by radiomics study of 68Ga-FAPI PET scan and 18F-FDG PET scan

Inclusion Criteria: Age greater than or equal to 18 years ECOG from 0 to 2 Histological diagnosis of Lobular Carcinoma of the breast based on a breast biopsy Patient naïve to any treatment for lobular breast carcinoma Women of childbearing age should have an adequate method of contraception Patient having voluntarily accepted to participate in the study and signed the informed consent Minimum tumor stage IIA Sufficient histological material in the biopsy or the surgical specimen, if the biopsy is insufficient Exclusion Criteria: PET scan contraindications: severe claustrophobia, unbalanced diabetes during 18F-FDG PET scans (fasting capillary blood sugar ≥ 11 mmol) Hormone therapy started 18F-FDG PET scan > 21 days Pregnant women, parturients and nursing mothers Persons deprived of liberty by a judicial or administrative decision Persons admitted to a health or social establishment for purposes other than research Adults who are the subject of a legal protection measure or who are unable to express their consent