title: See the unseen: Mesorectal lymph node metastases in prostate cancer.
abstract: BACKGROUND
  Our study is the first evaluation of nodal metastatic prostate cancer (PCa) to mesorectal lymph nodes (MLN) detected by (68) Ga-PSMA-PET/CT.
  
  
  METHODS
  We retrospectively analyzed 76 consecutive PCa patients who underwent (68) Ga-PSMA-PET/CT: 61 PCa patients with biochemical recurrence (BCR) after curative treatment and 15 high-risk PCa before primary therapy. We assessed PET-positive MLN, which are indicative for PCa.
  
  
  RESULTS
  We detected PET-positive lesions for PCa in (68) Ga-PSMA-PET/CT in 66 of 76 (87%) patients. Nodal disease was imaged in 47 of 66 (71%) patients. Indicative mesorectal nodal lesions for PCa were detected in 12 of 76 (15.8%) patients. The median number of PET-positive MLN was one per patient. Seven of twelve patients had recurrent PCa after radical prostatectomy with a median PSA value of 1.84 ng/ml (range 0.31-13). Five of twelve patients had untreated first diagnosed high-risk PCa with median PSA value of 90 ng/ml (range 4.6-93) at PET/CT, respectively. For all PET positive MLN a morphological correlate was found in CT (shortest diameter median 4 mm [range 4-21]; longest diameter median 7.5 mm [range 5-25]). After PET/CT, four patients with recurrent PCa received hormonal therapy, one patient was treated with directed radiation therapy of MLN, one patient received chemotherapy, and one patient was treated with pelvic lymph node dissection. Three high-risk PCa patients received hormonal therapy, and two patients were treated with adjuvant hormonal therapy after radical prostatectomy.
  
  
  CONCLUSIONS
  Detection and exact location of nodal metastasis for PCa is crucial for the choice of treatment and the patient's prognosis. (68) Ga-PSMA-PET/CT seems to improve the detection of nodal metastasis in PCa, especially concerning mesorectal lymph nodes.
authors.affiliation: Department of Urology, University Medical Center Göttingen, Göttingen, Germany.
authors.forename: Sameh
authors.initials: S
authors.lastname: Hijazi
authors.affiliation: Department of Nuclear Medicine, University Medical Center Göttingen, Göttingen, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Meller
authors.affiliation: Department of Urology, University Medical Center Göttingen, Göttingen, Germany.
authors.forename: Conrad
authors.initials: C
authors.lastname: Leitsmann
authors.affiliation: Department of Urology, University Medical Center Göttingen, Göttingen, Germany.
authors.forename: Arne
authors.initials: A
authors.lastname: Strauss
authors.affiliation: Institute for Diagnostic and Interventional Radiology, University Medical Center Göttingen, Göttingen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Ritter
authors.affiliation: Institute for Diagnostic and Interventional Radiology, University Medical Center Göttingen, Göttingen, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Lotz
authors.affiliation: Department of Nuclear Medicine, University Medical Center Göttingen, Göttingen, Germany.
authors.forename: Johannis
authors.initials: J
authors.lastname: Meller
authors.affiliation: Department of Urology, University Medical Center Göttingen, Göttingen, Germany.
authors.forename: Lutz
authors.initials: L
authors.lastname: Trojan
authors.affiliation: Department of Nuclear Medicine, University Medical Center Göttingen, Göttingen, Germany.
authors.forename: Carsten-Oliver
authors.initials: CO
authors.lastname: Sahlmann
mesh_terms: D006801:Humans; D008198:Lymph Nodes / Q000473:pathology*; D008207:Lymphatic Metastasis / Q000473:pathology*; D008297:Male; D009364:Neoplasm Recurrence, Local / Q000473:pathology*; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000473:pathology* / Q000601:surgery; D012189:Retrospective Studies
keywords: 68Ga-PSMA-PET/CT; PET/CT; PSMA; mesorectal lymph nodes; nodal metastases; prostate cancer