Urology & Kidney Disease News Fall 2009 - Cleveland Clinic

24 Urology & Kidney Disease News
Prostate Cancer
Brachytherapy and External Beam
Radiotherapy for Prostate Cancer: A Comparison
Jay P. Ciezki, MD
Cleveland Clinic investigators have been instrumental
in exploring differences among radiotherapeutic
options for prostate cancer. The differences may
best be understood by knowing the extent to which
radiation is scattered to the tissue around the
prostate (Figure 1). Because of the higher energy
of the radiation in external beam radiation, there is
high energy scatter that radiates a greater amount
of the rectum than brachytherapy, which makes use
of low-energy radiation that cannot scatter as far.
This geometric difference explains the results of the
comparison between brachytherapy and external
beam radiotherapy.
The first level of comparison is side effects. Cleveland
Clinic investigators participated in the largest and most
comprehensive assessment of side effects ever performed:
the PROST-QA multi-center trial, contributing . 42% off all
the brachytherapy patients in that trial At the two-year time
point, the increased rectal toxicity of external beam radiation
is already apparent. The external beam patients had a
3% incidence of rectal urgency at baseline, and a 16% rate
of rectal urgency at 2 years compared to the brachytherapy
Key Point:
A. B.
We have been investigating brachytherapy and external
beam radiation therapy in terms of side effects, biochemical
relapse-free survival and therapy outcomes. It appears that
brachytherapy is the logical radiotherapeutic choice for low-
role of external beam radiation therapy is potentially greater.
patients, who had a 4% rate at baseline and a 9% rate at 2
years. The interesting point about this parameter is that,
within the first 2 years, the rate is increasing for external
beam patients and decreasing for brachytherapy patients
(Figure 2).
The second point of comparison is biochemical relapse
free survival (bRFS). While it is a contentious end point, it
is often cited because it is a good indicator for the initiation
of salvage therapy for many patients. Figure 2 depicts the
bRFS comparison between the brachytherapy and external
beam patients within risk groups. There is no measurable
difference between the modalities within any risk group.
Finally, the outcome of therapy may be compared with
disease-specific mortality as an end point. This is seldom
done, yet it is the most unambiguous measure of treatment
success. Because prostate cancer treatment is associated
with such good outcomes, one expects very few deaths in