Somatostatin receptors expression in normal prostate gland assessed by 68Ga-DOTATOC PET/CT

Objectives The aim was to investigate somatostatin receptor (sstr) expression in normal prostate by determining the maximum standardized uptake value (SUVmax) of 68Ga-DOTATOC PET/CT in neuroendocrine tumor (NET) patients, without NET involvement of the prostate gland, in order to establish the reference standard.

Methods Sixty-four NET patients (24-97yrs, 60±14) underwent 68Ga-DOTATOC PET/CT. SUVmax of the prostate gland, normal liver, testes and gluteus muscles were evaluated. The prostate gland size was measured. Statistical analysis was performed using dedicated software (SPSS13).

Results Two patients had normal size of the prostate gland, 33 slight prostate enlargement, 17 prostate hypertrophy, 10 prostate hyperplasia and two had concomitant prostate cancer. Mean/median 68Ga-DOTATOC SUVmax values were: normal prostate 2.6±0.0, slightly enlarged prostate 4.2±1.6, prostatic hypertrophy 4.9±1.6, prostatic hyperplasia 5.0±1.5, prostate cancer 9.5±2.1, normal liver 7.3±1.8, testes 1.8±0.5, gluteus 1.0±0.2. The normal prostate gland had 3 times less sstr expression than normal liver tissue. Strong correlation was found between patient age and sstr expression in prostate/prostate size. No significant difference existed in sstr expression between prostatic hypertrophy and hyperplasia.

Conclusions Normal prostate tissue has very low sstr expression. Hypertrophic and hyperplastic prostate have higher sstr expression. Prostate hyperplasia and hypertrophy cannot be differentiated by 68Ga/DOTATOC PET/CT. Only concomitant prostate cancer in our group of patients was associated with higher sstr expression than the non-neoplastic liver tissue. Care should be taken not to overlook augmented 68Ga-DOTATOC uptake in the prostate gland of patients undergoing radiolabeled sst analogue PET/CT (especially if it is higher than in the liver tissue), which could indicate cancerous tissue.