CHICAGOA preliminary study of interstitial gene therapy for
recurrent prostate cancer shows that transrectal ultrasound can be
used effectively for planning delivery of the agent and assessing its
Transrectal ultrasound provides three-dimensional volume
assessment of the prostate gland for planning the deposition of the
gene therapy agent (PSA gene-regulated cytologic adenovirus),
Ulrike M. Hamper, MD, said at the 85th Annual Meeting of the
Radiological Society of North America (RSNA). It also allows
real-time monitoring of the delivery of the virus into the gland and
changes in histologic appearance after the virus has been deposited.
Dr. Hamper, associate professor of radiology and urology and director
of ultrasound, Johns Hopkins Medical Institutions, reported initial
results from a study of 30 men with prostate cancer that recurred
locally after radiotherapy who are being monitored after receiving
The men underwent a treatment planning session involving transrectal
ultrasound, which collected data for 3D modeling of the prostate
prior to gene therapy delivery. The men subsequently received
transperineal injection of the PSA gene-regulated adenovirus guided
by transrec-tal ultrasound using a standard brachy-therapy template.
Color Doppler imaging performed on days 4, 22, and 90 after gene
therapy delivery showed increased blood flow, compared with baseline
levels, which likely is due to prostatitis arising from the effect of
the virus on the prostate gland. Histologic examination revealed
signs of tumor persistence in addition to acute and chronic
PSA levels increased dramatically in 85% of men, which may be due to
the acute destructive effect exerted by the virus on PSA-producing
cells and the subsequent release of PSA by those cells, Dr. Hamper
suggested. PSA levels on post-treatment day 22 were lower in 77% of
men and unchanged in 1% of men. PSA levels increased by day 90 in
approximately 50% of men, were stable in 1%, and declined in 40%.
Changes were more pronounced in men who received the highest viral
dose. There was more vascularity in the prostate on days 4 and 22 and
a greater drop in PSA levels in men who received the highest number
of gene particles.
Further studies will assess the antitumor activity of the PSA
gene-regulated adenovirus, evaluate the systemic bioavailability and
distribution of the virus, and track the long-term effects of this
form of gene therapy.