RT Journal Article SR Electronic T1 Breast Cancer 18F-ISO-1 Uptake as a Marker of Proliferation Status JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 665 OP 670 DO 10.2967/jnumed.119.232363 VO 61 IS 5 A1 Elizabeth S. McDonald A1 Robert K. Doot A1 Anthony J. Young A1 Erin K. Schubert A1 Julia Tchou A1 Daniel A. Pryma A1 Michael D. Farwell A1 Anupma Nayak A1 Amy Ziober A1 Michael D. Feldman A1 Angela DeMichele A1 Amy S. Clark A1 Payal D. Shah A1 Hsiaoju Lee A1 Sean D. Carlin A1 Robert H. Mach A1 David A. Mankoff YR 2020 UL http://jnm.snmjournals.org/content/61/5/665.abstract AB The σ2 receptor is a potential in vivo target for measuring proliferative status in cancer. The feasibility of using N-(4-(6,7-dimethoxy-3,4-dihydroisoquinolin-2(1H)-yl)butyl)-2-(2-18F-fluoroethoxy)-5-methylbenzamide (18F-ISO-1) to image solid tumors in lymphoma, breast cancer, and head and neck cancer has been previously established. Here, we report the results of the first dedicated clinical trial of 18F-ISO-1 in women with primary breast cancer. Our study objective was to determine whether 18F-ISO-1 PET could provide an in vivo measure of tumor proliferative status, and we hypothesized that uptake would correlate with a tissue-based assay of proliferation, namely Ki-67 expression. Methods: Twenty-eight women with 29 primary invasive breast cancers were prospectively enrolled in a clinical trial (NCT 02284919) between March 2015 and January 2017. Each received an injection of 278–527 MBq of 18F-ISO-1 and then underwent PET/CT imaging of the breasts 50–55 min later. In vivo uptake of 18F-ISO-1 was quantitated by SUVmax and distribution volume ratios and was compared with ex vivo immunohistochemistry for Ki-67. Wilcoxon rank-sum tests assessed uptake differences across Ki-67 thresholds, and Spearman correlation tested associations between uptake and Ki-67. Results: Tumor SUVmax (median, 2.0 g/mL; range, 1.3–3.3 g/mL), partial-volume–corrected SUVmax, and SUV ratios were tested against Ki-67. Tumors stratified into the high–Ki-67 (≥20%) group had SUVmax greater than the low–Ki-67 (<20%) group (P = 0.02). SUVmax exhibited a positive correlation with Ki-67 across all breast cancer subtypes (ρ = 0.46, P = 0.01, n = 29). Partial-volume–corrected SUVmax was positively correlated with Ki-67 for invasive ductal carcinoma (ρ = 0.51, P = 0.02, n = 21). Tumor–to–normal-tissue ratios and tumor distribution volume ratio did not correlate with Ki-67 (P > 0.05). Conclusion: 18F-ISO-1 uptake in breast cancer modestly correlates with an in vitro assay of proliferation.