title: Aromatase imaging with [N-methyl-11C]vorozole PET in healthy men and women.
abstract: Aromatase, the last and obligatory enzyme catalyzing estrogen biosynthesis from androgenic precursors, can be labeled in vivo with (11)C-vorozole. Aromatase inhibitors are widely used in breast cancer and other endocrine conditions. The present study aimed to provide baseline information defining aromatase distribution in healthy men and women, against which its perturbation in pathologic situations can be studied.
  
  
  METHODS
  (11)C-vorozole (111-296 MBq/subject) was injected intravenously in 13 men and 20 women (age range, 23-67 y). PET data were acquired over a 90-min period. Each subject had 4 scans, 2 per day separated by 2-6 wk, including brain and torso or pelvis scans. Young women were scanned at 2 discrete phases of the menstrual cycle (midcycle and late luteal). Men and postmenopausal women were also scanned after pretreatment with a clinical dose of the aromatase inhibitor letrozole. Time-activity curves were obtained, and standardized uptake values (SUV) were calculated for major organs including brain, heart, lungs, liver, kidneys, spleen, muscle, bone, and male and female reproductive organs (penis, testes, uterus, ovaries). Organ and whole-body radiation exposures were calculated using OLINDA software.
  
  
  RESULTS
  Liver uptake was higher than uptake in any other organ but was not blocked by pretreatment with letrozole. Mean SUVs were higher in men than in women, and brain uptake was blocked by letrozole. Male brain SUVs were also higher than SUVs in any other organ (ranging from 0.48 ± 0.05 in lungs to 1.5 ± 0.13 in kidneys). Mean ovarian SUVs (3.08 ± 0.7) were comparable to brain levels and higher than in any other organ. Furthermore, ovarian SUVs in young women around the time of ovulation (midcycle) were significantly higher than those measured in the late luteal phase, whereas aging and cigarette smoking reduced (11)C-vorozole uptake.
  
  
  CONCLUSIONS
  PET with (11)C-vorozole is useful for assessing physiologic changes in estrogen synthesis capacity in the human body. Baseline levels in breasts, lungs, and bones are low, supporting further investigation of this tracer as a new tool for detection of aromatase-overexpressing primary tumors or metastases in these organs and optimization of treatment in cancer and other disorders in which aromatase inhibitors are useful.
authors.affiliation: Stony Brook University School of Medicine, Stony Brook, New York Brookhaven National Laboratory, Upton, New York anat.biegon@stonybrook.edu.
authors.forename: Anat
authors.initials: A
authors.lastname: Biegon
authors.affiliation: Brookhaven National Laboratory, Upton, New York.
authors.forename: David L
authors.initials: DL
authors.lastname: Alexoff
authors.affiliation: National Institute on Alcoholism and Alcohol Abuse, Bethesda, Maryland.
authors.forename: Sung Won
authors.initials: SW
authors.lastname: Kim
authors.affiliation: New York University Langone Medical Center, New York, New York.
authors.forename: Jean
authors.initials: J
authors.lastname: Logan
authors.affiliation: Institut de Recerca Hospital Universitari Vall d'Hebron, Universitat Autònoma de Barcelona, Alta Tecnologia, Barcelona, Spain; and.
authors.forename: Deborah
authors.initials: D
authors.lastname: Pareto
authors.affiliation: Brookhaven National Laboratory, Upton, New York.
authors.forename: David
authors.initials: D
authors.lastname: Schlyer
authors.affiliation: National Institute on Alcoholism and Alcohol Abuse, Bethesda, Maryland.
authors.forename: Gene-Jack
authors.initials: GJ
authors.lastname: Wang
authors.affiliation: Brookhaven National Laboratory, Upton, New York State University of New York at Stony Brook, Stony Brook, New York.
authors.forename: Joanna S
authors.initials: JS
authors.lastname: Fowler
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001141:Aromatase / Q000737:chemistry*; D047072:Aromatase Inhibitors / Q000737:chemistry*; D003952:Diagnostic Imaging; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D000077289:Letrozole; D008099:Liver / Q000187:drug effects / Q000528:radiation effects; D008297:Male; D008875:Middle Aged; D009570:Nitriles / Q000737:chemistry*; D049268:Positron-Emission Tomography / Q000379:methods*; D011874:Radiometry; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012737:Sex Factors; D012984:Software; D014230:Triazoles / Q000737:chemistry*; D014916:Whole-Body Irradiation; D055815:Young Adult
chemical_list: D047072:Aromatase Inhibitors; D009570:Nitriles; D019275:Radiopharmaceuticals; D014230:Triazoles; C060523:vorozole; D000077289:Letrozole; D001141:Aromatase
keywords: PET; aromatase inhibitors; biodistribution; dosimetry; vorozole