2845 - Correlation between Primary Uptake of [¹⁸F]AlF-NOTA-FAPI-04 and Molecular Subtypes of Breast Cancer

T. Liu^1,2, S. Xu², J. Liu², and J. Yu³; ¹Lung Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China, ²Department of Radiation Oncology and Shandong Provincial Key Laboratory of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China, ³Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China

Purpose/Objective(s): To investigate the correlation between primary lesion uptake of the tracer ¹⁸F-AlF-NOTA-fibroblast activation protein inhibitor (FAPI)-04 in PET/CT and molecular subtypes of breast cancer. Materials/

Methods: The study examined 42 breast lesions in 40 patients who had confirmed breast cancer using [18F]AlF-NOTA-FAPI 04 PET/CT imaging. Nine parameters obtained from PET images assessed tracer uptake in the breast lesions. The study used various statistical tests to compare the differences in parameters among different pathological grades, hormone receptor status, HER2 status, Ki-67 level, and five molecular subtypes of breast cancer: luminal A, luminal B (HER2-negative), luminal B (HER2-positive), HER2-positive and triple-negative breast cancer. The study also evaluated the correlation between each parameter, pathological features, and molecular subtypes. The classification performance of different parameters for each molecular subtype of breast cancer was assessed using the receiver operating characteristic (ROC) curve and area under the curve (AUC) analysis.
Results: Breast cancer lesions with higher pathological grade, hormone receptor negative, HER2 positive, and Ki-67=14% had higher [18F]AlF-NOTA-FAPI 04 uptake. The five different molecular subtypes exhibited varying levels of uptake. The luminal A and luminal B (HER2-negative) subtypes had relatively low uptake, while luminal B (HER2-positive), HER2-positive, and TN subtypes had relatively high uptake. A cut-off value 22.19 for TLF was identified to predict a luminal A subtype with 80% sensitivity and 97% specificity, resulting in an AUC of 0.941. For predicting a luminal B (HER2-negative) subtype, a cut-off value of 14.78 was determined, yielding a sensitivity of 64% and specificity of 71% using TBRblood with an AUC of 0.689. To predict a luminal B (HER2-positive) subtype, a cut-off value of 18.32 was found, resulting in a sensitivity of 100% and specificity of 67% using TBRblood with an AUC of 0.806. Lastly, a cut-off value of 13.45 was identified, yielding a sensitivity of 67% and specificity of 73% using SUVpeak with an AUC of 0.717 to predict a TN subtype tumor.
Conclusion: The uptake of [¹⁸F]AlF-NOTA-FAPI 04 is significantly correlated with the molecular subtypes of breast cancer and is expected to be used to detect different molecular subtypes.