title: Prostate cancer and prostate bed SPECT imaging with ProstaScint: semiquantitative correlation with prostatic biopsy results.
abstract: BACKGROUND
  ProstaScint (Cytogen Corporation, Princeton, NJ) murine monoclonal antibody imaging is FDA-approved for imaging of prostate cancer patients at high risk for metastatic disease and patients postprostatectomy with a rising serum prostate-specific antigen (PSA) level. ProstaScint is a murine monoclonal antibody which targets prostate-specific membrane antigen (PSMA). PSMA expression is upregulated in primary and metastatic prostate cancer. FDA Cytogen (Princeton, NJ) protocol studies using 111indium-labeled ProstaScint revealed correlation between areas of increased concentration in the prostate and biopsy-proven tumors in patients imaged pretherapy.
  
  
  METHODS
  In our study, four transverse, single-photon emission tomography (SPECT) images were isolated and regions of interest were selected and correlated with pretherapy prostate biopsy results. Prostate cancer and normal tissue prostate/muscle background (P/M) ratios were derived, so that postprostatectomy/radiation therapy patients could be evaluated for the presence of residual prostate cancer. Twenty-three pretherapy prostate cancer patients with quadrant/sextant biopsies had SPECT 96-hr 111indium ProstaScint pelvic images. The four transverse 1-cm slices above the midline penile blood pool were chosen, and four to six 27-30-pixel regions of interest were placed over the prostate bed. The background muscle region of interest was placed over the external obturator muscle region. The P/M ratio was calculated and compared to the quadrant/sextant prostatic biopsy result. The same procedure was applied to 17 posttherapy prostate cancer patients with rising PSA.
  
  
  RESULTS
  In the 23 pretherapy prostate cancer patients, there was a correlation between the P/M ratio of at least 3.0 in 32 of 35 prostatic cancer biopsy regions, and there was correlation with P/M ratios less than 3.0 in 82 of 89 negative biopsy regions. Seventeen posttherapy patients underwent ProstaScint studies. Six underwent biopsy, with typically one biopsy site per patient. All 6 had P/M ratios greater than 3.0 in the biopsied region. Five out of six biopsies revealed residual prostate cancer.
  
  
  CONCLUSIONS
  A prostate/muscle ratio was developed from 111indium ProstaScint regions of interest obtained on 1-cm SPECT transverse slices through the prostate bed in 23 patients preprostatic cancer therapy. A P/M ratio above 3.0 correlated in the majority of positive cases, and a P/M ratio below 3.0 was demonstrated in negative prostatic biopsy cases. The P/M ratio of above 3.0 or below 3.0 also separated those posttherapy prostate cancer patients with rising PSA who had residual prostate carcinoma in the prostate bed.
authors.affiliation: Department of Radiology, MetroHealth Medical Center/Case Western Reserve University, Cleveland, Ohio, USA.
authors.forename: D B
authors.initials: DB
authors.lastname: Sodee
authors.forename: R J
authors.initials: RJ
authors.lastname: Ellis
authors.forename: M A
authors.initials: MA
authors.lastname: Samuels
authors.forename: J P
authors.initials: JP
authors.lastname: Spirnak
authors.forename: W F
authors.initials: WF
authors.lastname: Poole
authors.forename: C
authors.initials: C
authors.lastname: Riester
authors.forename: D M
authors.initials: DM
authors.lastname: Martanovic
authors.forename: R
authors.initials: R
authors.lastname: Stonecipher
authors.forename: E M
authors.initials: EM
authors.lastname: Bellon
mesh_terms: D000368:Aged; D000911:Antibodies, Monoclonal; D001706:Biopsy; D006801:Humans; D007205:Indium Radioisotopes; D008297:Male; D008875:Middle Aged; D011467:Prostate / Q000473:pathology*; D017430:Prostate-Specific Antigen / Q000276:immunology; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
chemical_list: D000911:Antibodies, Monoclonal; D007205:Indium Radioisotopes; D017430:Prostate-Specific Antigen