TORONTO--Preliminary data on patients with rising prostate-specific
antigen (PSA) levels after radical prosta-tectomy suggest that
ProstaScint scin-tigraphy may offer a way to identify patients most
likely to benefit from radiation therapy. ProstaScint (capromab
pendetide) is an indium-111-labeled murine monoclonal antibody
diagnostic agent that attaches to the prostate-specific membrane antigen.
"In patients with localized disease, the most effective therapy
is radical prostatec-tomy," said Bennett Chin, MD, Department of
Radiology, Johns Hopkins Medical Institutions. However, he pointed
out, there is a relatively high incidence of tumor recurrence.
"We wanted to see if distant metastases could be detected in
patients who recur after surgery, to more appropriately select
patients who could benefit from standard radiation therapy," he
said at the 45th annual meeting of the Society of Nuclear Medicine.
The study included 63 prostate cancer patients with elevated PSA
levels (median, 1.25 ng/mL; range, 0.13 to 209 ng/mL) after
prostatectomy. Patients were examined via single-photon emission
computed tomography (SPECT) analysis 96 hours after injection of
ProstaScint. A second SPECT analysis at 120 hours postinjection was optional.
Of the 63 patients, 44 (70%) had abnormal SPECT scans. Five of these
44 (8%) had abnormal uptake in the prostate fossa and 39 (62%) had
abnormal uptake outside of the prostate fossa, including distant
lymph nodes. In addition, 10 patients (16%) had metastatic disease in
the para-aortic region without evidence of pelvic lymph node
involvement, also known as "skip metastases."
"Although follow-up confirmation is required, these preliminary
data suggest that indium-111 ProstaScint scintigraphy may identify
metastatic disease outside of the prostate region. Those men with
distant cancer recurrence may not benefit from conventional radiation
therapy and may be spared this unnecessary treatment and its adverse
side effects," Dr. Chin said.