Joint Program in Nuclear Medicine

Prostascint (Indium-111 Labeled Capromab Pendetide) Imaging

Christopher P. Fey, MD
Annick Van den Abbeele, MD

October 6, 1998

Presentation

A 73-year-old male with prostate cancer and questionable lymph node on CT and with a negative bone scan presented for staging.

Imaging Technique

96 hours after injection with In-111-labeled Prostascint, planar and SPECT images were obtained. At this time, a blood pool scan was also performed, using Tc-99m-labeled RBCs and dual acquisition was obtained.

Imaging Findings

fig 1 - axial CT shows questionable node near aortic bifurcation. fig 2 - planar Prostascint and RBC images show no activity in the region of the node fig 3 - posterior Prostascint images show a focus of uptake in the LUQ - RBC images show this finding has intense blood pool activity fig 4 - axial CT shows this finding to be a splenule fig 5 - axial SPECT images show blood pool activity in the femoral vessels and penile base - Prostascint uptake is seen in the prostate

Differential Diagnosis

Prostascint's physiologic distribution is that of a whole murine antibody. Uptake is seen in prostate metastases, primary prostate neoplasms, and normal prostate tissue. Prostascint shows blood pool activity as well as bowel activity.

Diagnosis

No evidence of extraprostatic tumor on this scan.

Discussion

The Antibody Prostascint is a whole murine monoclonal antibody which is directed against prostate membrane specific antigen (PMSA), a transmembrane glycoprotein expressed by prostate epithelial cells. PMSA expression is higher in prostate adenocarcinoma cells than in nonmalignant cells, and it is higher in metastatic lesions than in primary lesions.

Indications Prostascint may be useful to evaluate postprostatectomy patients with rising PSA who have an otherwise negative or equivocal workup for metastases. Another potential role for Prostascint (controversial) is in the staging of newly diagnosed prostate cancer.

Pearls -Tomographic (SPECT) acquisitions are essential -Prostascint studies should be interpreted with the aid of a CT scan. -Use dual acquisition with Tc-99m labeled RBC blood pool images to distinguish blood pool structures. -Use delayed views to help clarify activity within the bowel if necessary.

References

Kahn et al., “111-Indium Capromab Pendetide in the Evaluation of Patients with Residual or Recurrent Prostate Cancer after Radical Prostatectomy,” J Urol (1998 Jun) 159(6):2041-6.

Lamb et al., “Capromab Pendetide: A Review of Its Use as an Imaging Agent in Prostate Cancer,” Drugs Aging (1998 April) 12(4):293-304.

Kahn et al., “Radioimmunoscintigraphy with In-111-labeled Capromab Pendetide Predicts Prostate Cancer Response to Salvage Radiotherapy after Failed Radical Prostatectomy,” Journal of Clinical Oncology, vol 16, no 1, (Jan) 1998 pp. 284-289.

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J. Anthony Parker, MD PhD, Tony_Parker@bidmc.harvard.edu