Assessment of Progesterone Receptors in Breast Carcinoma by PET with 21-18F-Fluoro-16α,17α-[(R)-(1′-α-furylmethylidene)Dioxy]-19-Norpregn-4-Ene-3,20-Dione

This first-in-human study was designed to evaluate the safety and dosimetry of the progesterone analog 21-F-18-fluoro-16 alpha, 17 alpha-[(R)(1'-alpha-furylmethylidene)dioxy]-19-norpregn-4-ene-3,20-dione (F-18-FFNP), as well the feasibility of imaging tumor progesterone receptors (PRs) by PET in breast cancer. Methods: Women with breast cancer underwent PET with F-18-FFNP. Tumor F-18-FFNP uptake was assessed semiquantitatively by determining maximum standardized uptake value and tumor-to-normal breast (T/N) activity ratio and by Logan graphical analysis. The PET results were correlated with estrogen receptor (ER) and PR status, assessed by in vitro assays of the tumor tissue. The biodistribution of F-18-FFNP was measured in patients by whole-body PET, and human dosimetry was estimated. Results: Twenty patients with 22 primary breast cancers (16 PR-positive [PR+] and 6 PR-negative [PR-]) were evaluated. Tumor maximum standardized uptake value was not significantly different in PR+ and PR- cancers (mean +/- SD, 2.5 +/- 0.9 vs. 2.0 +/- 1.3, P = 0.386), but the T/N ratio was significantly greater in the PR+ cancers (2.6 +/- 0.9 vs. 1.5 +/- 0.3, P = 0.001). In addition, there was a significant correlation between distribution volume ratio and T/N ratio (r = 0.89; P = 0.001) but not between distribution volume ratio and either PR status or standardized uptake value, likely because of small sample size. On the basis of whole-body PET data in 12 patients, the gallbladder appeared to be the dose-limiting organ, with an average radiation dose of 0.113 mGy/MBq. The whole-body dose was 0.015 mGy/MBq, and the effective dose was 0.020 mSv/MBq. No adverse effects of F-18-FFNP were encountered. Conclusion: F-18-FFNP PET is a safe, noninvasive means for evaluating tumor PRs in vivo in patients with breast cancer. The relatively small absorbed doses to normal organs allow for the safe injection of up to 440 MBq of F-18-FFNP.