Initial Results of 68Ga-FAPI-46 PET/MRI to Assess Response to Neoadjuvant Chemotherapy in Breast Cancer.

Backhaus P; Burg MC; Asmus I; Pixberg M; Büther F; Breyholz HJ; Yeh R; Weigel SB; Stichling P; Heindel W; Bobe S; Barth P; Tio J; Schäfers M

Research article (journal) | Peer reviewed

Abstract

Improving imaging-based response after neoadjuvant chemotherapy (NAC) in breast cancer assessment could obviate histologic confirmation of pathologic complete response (pCR) and facilitate deescalation of chemotherapy or surgery. Fibroblast activation protein inhibitor (FAPI) PET/MRI is a promising novel molecular imaging agent for the tumor microenvironment with intense uptake in breast cancer. We assessed the diagnostic performance of follow-up breast 68Ga-FAPI-46 (68Ga-FAPI) PET/MRI in classifying the response status of local breast cancer and lymph node metastases after completion of NAC and validated this approach immunohistochemically. Methods: In women who completed NAC for invasive breast cancer, follow-up 68Ga-FAPI PET/MRI and corresponding fibroblast activation protein (FAP) immunostainings were retrospectively analyzed. Metrics of 68Ga-FAPI uptake and FAP immunoreactivity in women with or without pCR were compared using the Mann-Whitney U test. Diagnostic performance to detect remnant invasive cancer was calculated for tracer uptake metrics using receiver-operating-characteristic curves and for masked readers' visual assessment categories of PET/MRI and MRI alone. Results: Thirteen women (mean age ± SD, 47 ± 9 y) were evaluated. Seven of the 13 achieved pCR in the breast and 6 in the axilla. FAP immunoreactivity was significantly associated with response status. The 68Ga-FAPI PET/MRI mean breast tumor-to-background ratio was 0.9 (range, 0.6-1.2) for pCR and 2.1 (range, 1.4-3.1) for no pCR (P = 0.001). Integrated PET/MRI could classify breast response correctly in all 13 women based on readers' visual assessment or tumor-to-background ratio. Evaluation of MRI alone resulted in at least 2 false-positives. For lymph nodes, PET/MRI readers had at least 2 false-negative classifications, whereas MRI alone resulted in 2 false-negatives and 1 false-positive. Conclusion: To our knowledge, this was the first analysis of 68Ga-FAPI PET/MRI for response assessment after NAC for breast cancer. The diagnostic performance of PET/MRI in a small study sample trended toward a gain over MRI alone, clearly supporting future prospective studies.

Details about the publication

JournalJournal of Nuclear Medicine
Volume64
Issue5
Page range717-723
StatusPublished
Release year2023 (31/05/2023)
Language in which the publication is writtenEnglish
DOI10.2967/jnumed.122.264871
Link to the full texthttps://jnm.snmjournals.org/content/64/5/717.long
KeywordsFemale; Humans; Breast Neoplasms; Gallium Radioisotopes; Neoadjuvant Therapy; Prospective Studies; Retrospective Studies; Magnetic Resonance Imaging; Positron-Emission Tomography; Positron Emission Tomography Computed Tomography; Fluorodeoxyglucose F18; Quinolines; Tumor Microenvironment

Authors from the University of Münster

Asmus, Inga
Clinic for Nuclear Medicine
Backhaus, Philipp
Clinic for Nuclear Medicine
Barth, Peter Josef
Gerhard Domagk Institute of Pathology
Bobe, Stefanie
Gerhard Domagk Institute of Pathology
Breyholz, Hans-Jörg
Clinic for Nuclear Medicine
Burg, Matthias Christian
Clinic of Radiology
Büther, Florian
Clinic for Nuclear Medicine
Heindel, Walter Leonhard
Clinic of Radiology
Pixberg, Michaela
Clinic for Nuclear Medicine
Schäfers, Michael
Clinic for Nuclear Medicine
Stichling, Patricia Maria
Clinic of Radiology
Weigel, Stefanie Bettina
Clinic of Radiology