TY - JOUR T1 - Imaging Androgen Receptors in Breast Cancer with <sup>18</sup>F-Fluoro-5α-Dihydrotestosterone PET: A Pilot Study JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 22 LP - 28 DO - 10.2967/jnumed.121.262068 VL - 63 IS - 1 AU - Heather Jacene AU - Mofei Liu AU - Su-Chun Cheng AU - Amanda Abbott AU - Shipra Dubey AU - Keisha McCall AU - Diane Young AU - Mayzie Johnston AU - Annick D. Van den Abbeele AU - Beth Overmoyer Y1 - 2022/01/01 UR - http://jnm.snmjournals.org/content/63/1/22.abstract N2 - Most breast cancers express androgen receptors (ARs). This prospective imaging substudy explored imaging of ARs with 18F-fluoro-5α-dihydrotestosterone (18F-FDHT) PET in patients with metastatic breast cancer (MBC) receiving selective AR modulation (SARM) therapy (GTx-024). Methods: Eleven postmenopausal women with estrogen receptor–positive MBC underwent 18F-FDHT PET/CT at baseline and at 6 and 12 wk after starting SARM therapy. Abnormal tumor 18F-FDHT uptake was quantified using SUVmax. AR status was determined from tumor biopsy specimens. 18F-FDHT SUVmax percentage change between scans was calculated. Best overall response was categorized as clinical benefit (nonprogressive disease) or progressive disease using RECIST 1.1. Results: The median baseline 18F-FDHT SUVmax was 4.1 (range, 1.4–5.9) for AR-positive tumors versus 2.3 (range, 1.5–3.2) for AR-negative tumors (P = 0.22). Quantitative AR expression and baseline 18F-FDHT uptake were weakly correlated (Pearson ρ = 0.39, P = 0.30). Seven participants with clinical benefit at 12 wk tended to have larger declines in 18F-FDHT uptake than did those with progressive disease both at 6 wk after starting GTx-024 (median, −26.8% [range, −42.9% to −14.1%], vs. –3.7% [range,−31% to +29%], respectively; P = 0.11) and at 12 wk after starting GTx-024 (median, −35.7% [range, −69.5% to −7.7%], vs. –20.1% [range, −26.6% to +56.5%], respectively; P = 0.17). Conclusion: These hypothesis-generating data suggest that 18F-FDHT PET/CT is worth further study as an imaging biomarker for evaluating the response of MBC to SARM therapy and reiterate the feasibility of including molecular imaging in multidisciplinary therapeutic trials. ER -