Prospective Clinical Trial of ¹⁸F-Fluciclovine PET/CT for Determining the Response to Neoadjuvant Therapy in Invasive Ductal and Invasive Lobular Breast Cancers.

Abstract

¹⁸F-labeled 1-amino-3-fluorocyclobutane-1-carboxylic acid (¹⁸F-fluciclovine) is a leucine analog radiotracer that depicts amino acid transport into cells. ¹⁸F-fluciclovine PET/CT visualizes malignancy, including prostate cancer, invasive ductal breast cancer, and invasive lobular breast cancer. Whether changes in ¹⁸F-fluciclovine avidity reflect changes in tumor burden resulting from treatment has not been shown. In this prospective clinical trial (clinical trials.gov: NCT01864083), changes in ¹⁸F-fluciclovine avidity after neoadjuvant therapy were compared to breast cancer therapy response, as determined by residual tumor burden on pathology, were evaluated. <b>Methods:</b> Twenty-four women with a new diagnosis of locally advanced invasive ductal breast cancer (<i>n</i> = 18) or invasive lobular breast cancer (<i>n</i> = 6) underwent ¹⁸F-fluciclovine PET/CT before and after the completion of neoadjuvant systemic therapy. SUV_max, SUV_mean, metabolic tumor volume, and total lesion avidity were obtained for the primary breast tumor, axillary lymph nodes, and extraaxillary lymph nodes on each examination and corrected for background ¹⁸F-fluciclovine avidity. The relationship between changes in ¹⁸F-fluciclovine avidity and the percentage of reduction of tumor on pathology was assessed with the Spearman rank correlation. <b>Results:</b> The median decrease in the corrected SUV_max of the primary breast lesions was 99% (range, 33%-100%). The median reduction of tumor on pathology was 92% (range, 10%-100%). Changes in ¹⁸F-fluciclovine avidity were strongly correlated with the percentage of reduction of tumor on pathology (Spearman ρ, 0.79; 95% CI, 0.56-0.90; <i>P</i> < 0.001). <b>Conclusion:</b> Changes in ¹⁸F-fluciclovine avidity strongly correlated with the tumor response on pathology in this pilot study.