PRESS RELEASE. PRINCETON, N.J., Dec. 3 /PRNewswire-FirstCall/ -- Cytogen Corporation (Nasdaq: CYTO), a product-driven, oncology-focused company, today announced that data from clinical studies relating to its ProstaScint(R) molecular imaging agent (Capromab pendetide), was presented at the 89th Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA), held November 30 through December 5, 2003, in Chicago, IL.

A presentation of data from a large, retrospective outcomes study entitled
"Multifocal Capromab Pendetide (ProstaScint) Uptake in the Central Abdominal
Region: What Does It Mean?" by Michael Haseman, M.D., President of the
Radiological Associates of Sacramento, concluded that "the pattern of
multifocal capromab pendetide [ProstaScint] uptake in the central abdominal
region indicates a poor prognosis." In a study of 341 patients, Dr. Haseman's
results showed that those patients having this ProstaScint scan finding were
2.8 times more likely to have died during the four-year follow-up period than
those without.
"Nuclear medicine physicians experienced in the use of ProstaScint believe
that multifocal uptake in the central abdominal region probably represents
metastatic disease in retroperitoneal and/or mesenteric lymph nodes, yet there
has been some uncertainty given the limited histopathologic correlation that
has been obtained in these patients," said Dr. Haseman. "Our outcome study
shows that this pattern of uptake with ProstaScint is associated with a poor
prognosis, adding support to the belief that this does indeed indicate
metastatic disease."
Another presentation entitled "The Influence of Radioimmunoscintigraphy on
Post-Prostatectomy Radiotherapy Decision-Making" by Ashesh Jani, M.D., a
radiation oncologist at the University of Chicago/University of Illinois,
concluded that "Incorporating [ProstaScint]-uptake was found to result in
significant modification in post-prostatectomy clinical target volume
definition." In this study, the records, image data, and treatment plans of
25 consecutive post-prostatectomy patients who received external beam
radiotherapy post-prostatectomy and who underwent a ProstaScint scan for
aiding treatment volume definition were reviewed. A vessel registration
technique developed at University of Chicago/University of Illinois was
implemented to project the region(s) of uptake on the ProstaScint scan into
the planning computed tomography (CT) scan to assist in defining the clinical
target volume. For each patient, the clinical target volume that would have
been treated prior to this ProstaScint/CT fusion was compared with that
defined after the fusion. Additionally, the treatment plan generated using
clinical target volume prior to this ProstaScint/CT fusion was compared with
that defined after the fusion to quantify the differences on the bladder and
rectum dose volume histograms. Incorporating ProstaScint/CT fusion was found
to result in significant modification in post-prostatectomy clinical target
volume definition. The dosimetric consequences of the clinical target volume
modifications on the rectum were demonstrated not to be significant. Although
the clinical target volume modifications with ProstaScint/CT fusion do not
appear to adversely affect integral dose to the bladder, they do appear to
have an effect on the volume of bladder receiving high doses. However,
observed rates of grade 3 and 4 GI and GU toxicities were quite low,
suggesting that treatment to the ProstaScint/CT fusion modified clinical
target volume is tolerable.
"It is always great to see a positive impact on treatment planning results
when the information from a functional imaging study can be used to clarify
the details of an anatomical study," said Michael J. Blend, Ph.D., D.O.,
Professor and Director of the Section of Nuclear Medicine at University of
Illinois at Chicago and co-author of the study. "In this study, nuclear
medicine physicians and radiation oncologists working together were able to
show improved targeting of suspicious recurrent cancerous tissue in post-
prostatectomy patients when the ProstaScint examination was used to guide 3D-
CRT treatment planning. ProstaScint was able to define a more precise
clinical target volume without causing any significant increase to non-target
tissue damage. This information gave the radiation oncologist greater
confidence in deciding who to treat and who not to treat."
A second presentation by Dr. Jani entitled "Analysis of the Impact of
Radioimmunoscintigraphy on Post-Prostatectomy Radiotherapy Clinical Target
Volume Definition" concluded that "[ProstaScint] was found to be instrumental
in the setting of post-prostatectomy radiotherapy decision-making for the
identification of patients with disease not likely to benefit from
radiotherapy and guiding general radiotherapy treatment volume definition."
In this study, the charts of 54 consecutive patients having prostate cancer
who underwent radical retropubic prostatectomy and were referred to University
of Chicago/University of Illinois hospital consortium for consideration of
external beam radiotherapy for radical retropubic prostatectomy failure {n=45}
[or for high-risk of post-radical retropubic prostatectomy failure {n=9}], and
for whom a ProstaScint scan was ordered for aiding radiotherapy decision-
making were reviewed. Bone scan and/or computed tomography (CT) scan of the
abdomen/pelvis were normal in all patients for whom these tests were ordered
immediately prior to or at the time of the radiation oncology consultation.
Of the 54 patients originally referred for post-radical retropubic
prostatectomy radiotherapy, the initial decision was to recommend radiotherapy
in all 54 patients - in 52 cases to the prostate fossa only and in 2 cases to
prostate fossa plus pelvis. The ProstaScint uptake was read as follows:
prostate fossa only in 42 patients, prostate fossa plus pelvis in 8 patients,
prostate fossa plus extrapelvic in 2 patients, prostate fossa plus pelvis and
extrapelvic in 1 patient, and no uptake in 1 patient. After knowledge of the
ProstaScint results, the decision to withdraw the radiotherapy recommendation
was made in 4 of the 54 patients (7.4%). Furthermore, ProstaScint changed the
general treatment volume (i.e., prostate fossa only to prostate fossa plus
pelvis) in 6 of the 54 patients (11.1%). In total, ProstaScint altered the
radiotherapy decision in a statistically significant 10 of the 54 patients
(18.5%), (p=0.004, chi-square).
"The first data from a large, retrospective outcomes study presented at
the RSNA meeting serves to validate that ProstaScint, in conjunction with
other diagnostic information, is an important and clinically useful molecular
imaging procedure," said Michael D. Becker, President and Chief Executive
Officer of Cytogen Corporation. "The two additional investigational studies
presented at RSNA reflect Cytogen's ongoing commitment to work with radiation
oncologists and other physicians to research, develop and implement advanced
molecular imaging techniques to identify patients with disease who are not
likely to benefit from radiotherapy or to determine the extent and location of
disease so that therapy can be directed with greater precision to cancerous
cells and reduced damage to surrounding healthy tissue. In this
investigational setting, ProstaScint altered the radiotherapy decision in
nearly 19% of the patients studied."
Cytogen's ProstaScint imaging agent is the first commercial product
targeting prostate-specific membrane antigen (PSMA), a cell-surface protein
that is expressed on prostate cancer cells at all stages of disease, including
advanced or metastatic disease. ProstaScint consists of a murine monoclonal
antibody directed against PSMA that is linked to the radioisotope Indium-111.
A radioisotope is an element, which, because of nuclear instability, undergoes
radioactive decay and emits radiation. ProstaScint images are acquired using
a common gamma camera. Due to the selective expression of PSMA by prostate
cancer cells, the ProstaScint imaging procedure can detect the extent and
spread of prostate cancer in the body.

NOTE:
ProstaScint is indicated as a diagnostic imaging agent in newly diagnosed
patients with biopsy-proven prostate cancer, thought to be clinically
localized after standard diagnostic evaluation and who are thought to be at
high risk for pelvic lymph node metastases. ProstaScint is also indicated in
post-prostatectomy patients and a negative or equivocal standard metastatic
evaluation in whom there is a high clinical suspicion of occult metastatic
disease. This press release describes clinical applications and imaging
performance that differs from that reported in the ProstaScint package insert.
A copy of the full prescribing information for ProstaScint may be obtained
in the United States from Cytogen Corporation by calling toll free 800-833-
3533 or by visiting the Company's web site at http://www.cytogen.com.

About Cytogen Corporation
Cytogen Corporation of Princeton, NJ is a product-driven, oncology-focused
biopharmaceutical company. Cytogen markets proprietary and licensed oncology
products through its in-house specialty sales force: Quadramet(R) (a skeletal
targeting therapeutic radiopharmaceutical for the relief of pain due to bone
metastases); ProstaScint(R) (a monoclonal antibody-based imaging agent used to
image the extent and spread of prostate cancer); and NMP22(R) BladderChek(TM)
(a point-of-care, in vitro diagnostic test for bladder cancer). Cytogen has
exclusive U.S. marketing rights to Combidex(R), an ultrasmall
superparamagnetic iron oxide contrast agent for magnetic resonance imaging of
lymph nodes that is pending clearance by the U.S. Food and Drug
Administration. Cytogen's pipeline comprises product candidates at various
stages of clinical development, including fully human monoclonal antibodies
and cancer vaccines based on PSMA (prostate specific membrane antigen)
technology, which was exclusively licensed from Memorial Sloan-Kettering
Cancer Center. Cytogen also conducts research in cellular signaling through
its AxCell Biosciences research division in Newtown, PA. For more
information, please visit the Company's website at http://www.cytogen.com, which is
not part of this press release.

This press release contains certain "forward-looking" statements within
the meaning of the Private Securities Litigation Reform Act of 1995 and
Section 21E of the Securities Exchange Act of 1934, as amended. All
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There are a number of important factors that could cause Cytogen's results to
differ materially from those indicated by such forward-looking statements. In
particular, Cytogen's business is subject to a number of significant risks,
which include, but are not limited to, the risk of obtaining the necessary
regulatory approvals, the risk of whether products result from development
activities, the risk of shifts in the regulatory environment affecting sales
of Cytogen's products such as third-party payor reimbursement issues, and the
risk associated with Cytogen's dependence on its partners for development of
certain projects. Cytogen cannot guarantee that Cytogen will actually achieve
the plans, intentions or expectations disclosed in any such forward-looking
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historical results of operations and those discussed in such forward-looking
statements and the risks stated above for various reasons, including, but not
limited to, Cytogen's ability to carry out its business and financial plans,
to successfully commercialize Quadramet(R), to determine and implement the
appropriate strategic initiative for its AxCell Biosciences subsidiary, to
fund development necessary for existing products and to pursue new product
opportunities, to integrate in-licensed products such as NMP22(R)
BladderChek(TM), to establish and successfully complete clinical trials where
required for product approval, to obtain foreign regulatory approvals for
products and to establish marketing arrangements in countries where approval
is obtained, and other factors discussed in Cytogen's Form 10-K for the year
ended December 31, 2002, as amended, and from time-to-time in Cytogen's other
filings with the Securities and Exchange Commission. Any forward-looking
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acquisitions, mergers, dispositions, joint ventures or investments Cytogen may
make. Cytogen does not assume, and specifically disclaims, any obligation to
update any forward-looking statements, and these statements represent
Cytogen's current outlook only as of the date given.



SOURCE Cytogen Corporation
Web Site: http://www.cytogen.com