The side effect profiles of various therapeutic modalities used in
the definitive management of prostate cancer differ significantly,
reported Tamara LaCouture, MD, and colleagues at the American Society
for Therapeutic Radiology and Oncology (ASTRO) meeting. Affiliated
with Allegheny University of the Health Sciences, Philadelphia,
Pennsylvania, Cooper Hospital/University Medical Center, Camden, New
Jersey, and Albert Einstein Northern Division, Philadelphia, the
investigators compared the prostate-specific antigen (PSA) response
and treatment-related morbidity associated with prostate seed
implantation vs external-beam radiotherapy for prostate cancer.
A total of 243 consecutive patients treated for cure were studied.
Patients who underwent prostate seed implantation were divided into
two groups: low-risk patients were defined as those with a
pretreatment PSA value £ 15 ng/mL, a
Gleason score £ 7, and a disease
stage of T2A or lower; all other patients were defined as high risk.
Low-risk patients were treated with seed implantation alone, whereas
high-risk patients underwent seed implantation 2 to 4 weeks after
external beam radiotherapy.
The patients who underwent brachytherapy alone received seed
implantation in a total dose of either 120 Gy (palladium-103) or 170
Gy (iodine-125) to the prostate volume. For those who initially
received combination therapy, the boost was delivered using seeds,
with a brachytherapy dose of 75 Gy (palladium-103) or 125 Gy
(iodine-125). For patients who received definitive external-beam
radiotherapy, doses to the prostate ranged from 66.6 to 70.2 Gy.
Varying Side Effects
A different symptom profile was apparent among patients who received
seeds compared with patients who received external-beam radiotherapy.
The low-risk patients who underwent external-beam radiotherapy had a
statistically significant increase in rectal symptoms compared with
patients who underwent seed implantation alone (78% vs 11%; P £
.001). The high-risk patients who underwent external-beam
radiotherapy alone also experienced more rectal symptoms than the
patients who underwent combined-modality therapy (76% vs 26%; P £ .001).
In contrast, there appeared to be an increase in urinary
irritative/obstructive symptoms of Radiation Therapy Oncology Group
(RTOG) grades 3 and 4 in patients who underwent seed implantation vs
those who did not. The mean duration of these irritative urinary
symptoms was longer in patients who received brachytherapy than in
those who received external-beam radiotherapy alone (4.5 vs 9.1
months; P £ .001).
Biochemical Control Data
With regard to PSA response, a significant difference was
demonstrated at 18 months follow-up in the low-risk
populations; this difference persisted after control for hormonal
manipulation. At 36 months of follow-up, however, there appeared to
be no significant difference, with mean PSA values being £
1.2 ng/mL for both groups. The investigators postulated that the
significant difference seen at 18 months of follow-up may represent
the different kinetics of PSA decline in patients treated with seed
Similar data were noted for the high-risk patients, with a
statistically significant increase in the 6-, 12-, and 18-month
follow-up PSA values in patients who underwent external-beam
radiotherapy. The investigators postulated that this may be secondary
to a more rapid decline in PSA in the combined-modality group
resulting from a higher incidence of hormonal manipulation. In view
of the PSA kinetics following seed implantation, a minimum of 24
months of follow-up may be necessary to make any meaningful
comparisons of biochemical control.