EURURO Vol. 72 No. 4

622 656

we have termed vessel-sparing radiotherapy. Key compo-
nents to the use of vessel-sparing radiotherapy are (1)
utilization of MRI to more accurately delineate the prostate
and critical vascular elements and (2) use of image-guided
radiotherapy to allow sparing of nearby periprostatic tissues.
Our results demonstrate that at 5 yr after vessel-sparing
radiotherapy, 88% of patients are still sexually active with or
without the use of aids. These results appear promising,
especially considering that most patients had intermediate or
high risk, 61% received a combination of IMRT with brachy-
therapy, and 33% received ADT, both of which have been
shown to potentially impact potency preservation rates
One concern that arises when attempting a nerve-
sparing radical prostatectomy is the potential for higher
rates of biochemical failure if not performed on well-
selected patients . This is also a concern when
limiting the radiation dose to nearby vascular structures.
MRI allows more accurate definition of the prostate apex,
and in most patients the apex was separated farther from
critical vascular elements when compared to CT-based
approaches . This allowed for adequate coverage of
the prostate while sparing vascular structures involved in
erectile function. In addition to achieving high rates of
erectile function preservation, tumor control was excellent
and did not appear to be jeopardized.
Clear demonstration of the functional anatomic approach
with radiotherapy has been challenging. However, many
have accepted that the avoidance of surrogate structures,
such as the penile bulb, has an important role inmaintenance
of functional erections. Early reports by Merrick et al for
baseline-potent men showed a potency preservation rate of
only 39% at 6 yr after treatment. This preservation rate was
especially low in light of the threshold IIEF-5 score of 11
used to define post-treatment erectile function. With a
change in radiation technique to spare the proximal penis,
Merrick et al subsequently reported a potency preser-
vation rate of 51% at 3 yr for a potency definition of IIEF-5
score 13. Our results continue to build on these earlier
functional anatomic efforts, anddemonstrate the importance
of further sparing of critical erectile structures. Using a
stricter IIEF-5 score of 16 to define erectile function, we
report an erectile function preservation rate of 67% at 5 yr.
Loss of erectile function appears to depend on the
treatment modality ). Prospective longitudinal
evidence has consistently demonstrated that radiotherapeu-
tic approaches result in less short-term and intermediate-
term sexual dysfunction when compared to surgical
approaches. This is despite the fact that most of the evidence
until recently came from nonrandomized comparisons in
which radiotherapy-treated patients were older, had worse
baseline erectile function, and usually suffered froma greater
burden of comorbidities that could impact erectile function.
However, results from the ProtecT trial, which randomized
men between active monitoring, nerve-sparing prostatec-
tomy, and conventional EBRT with a short course of ADT,
have recently been published . The authors reported that
at 2 yr after treatment, only 19% of men who underwent a
nerve-sparing radical prostatectomy and 34% of men who
underwent radiotherapy and short-term ADT had erections
firm enough for intercourse. These findings are consistent
with the modeling results we present for predicting erectile
function after treatment using our patients’ baseline
characteristics (24%, 42%, and 78% had erections firm enough
for intercourse after nerve-sparing prostatectomy, conven-
tional EBRT, and vessel-sparing radiotherapy; p < 0.001).
Our data demonstrate that 87% of baseline-potent men
were able to maintain functional erections suitable for
intercourse at 2 yr after treatment. This should be compared
to other prospective longitudinal series or randomized trial
data that consistently show that functional erections in
baseline-potent men are maintained in 29–43% of those who
undergo radical prostatectomy and 45–69% of those who
undergo conventional EBRT ) In addition,
our unique primary endpoint of maintenance of being
‘‘sexually active’’ allowed us to capture non-intercourse
declines in sexual function. Sanda et al utilizing the
PROSTQA cohort, reported that 66% ofmen at 2 yr after radical
prostatectomy were using sexual aids, but only 35% of men
had erections suitable for intercourse. This demonstrates that
there are probably a significant number of menwho are using
sexual aids who remain sexually active, even if not able to
have erections suitable for intercourse. The maintenance of
sexual activity is probably still of value to patients (and their
partners) even if unable to achieve erections firm enough for
intercourse, and should be further studied.
Although not the primary focus of the present study,
biochemical control rates were excellent and on par with
similar series using dose-escalated radiotherapy and/or
selective use of brachytherapy boost and ADT. The
ASCENDE-RT randomized trial recently reported that with
brachytherapy boost and ADT, the 6.5-yr rate of bRFS for
intermediate-risk men was 94%, which is comparable to our
study at 96% . Similarly, our low-risk patients had 100%
biochemical control, similar to the Memorial Sloan Ketter-
ing result of 99% . This suggests that sparing critical
erectile structures did not compromise tumor control.
Our study was limited in that there are probably many
non-radiotherapeutic causes of erectile dysfunction that
were not fully captured (ie, psychological and social causes).
In addition, we attempted to be fully transparent in our
cohort details and results, but selection bias is possible for
men who are more motivated to preserve erectile function.
Furthermore, a formal comparator arm was not included
given the phase 2 single-arm study design, and there are
limitations to model-based comparisons (EPIC scores were
not directly collected andwere generated from IIEF-5 scores).
However, themodel we usedwas created using the PROSTQA
cohort, which consists of patients treated at experienced
centers, and accounts for multiple baseline patient and
treatment factors that impact erectile function rates (age, use
of ADT, baseline sexual health-related quality of life, etc). A
formal multicenter randomized trial comparing convention-
al radiotherapy to vessel-sparing radiotherapy is being
developed. In addition, our cohort had a small number of
high-risk patients, and long-termADTwas not utilized in our
study, so caution is requiredwhen extrapolating these results
to men treated with long-term ADT.
E U R O P E A N U R O L O G Y 7 2 ( 2 0 1 7 ) 6 1 7 – 6 2 4 622