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failure. The 5- and 10-yr rates of bRFS were 99.3% and 89.9%,
respectively (Supplementary Fig. 1). At 5 yr the biochemical
failures were limited to the NCCN high-risk group
(Supplementary Fig. 2). The 10-yr bRFS for low-risk,
intermediate-risk, and high-risk prostate cancer was
100.0%, 89.2%, and 87.8%, respectively.
3.4. Comparison of vessel-sparing radiotherapy to standard
EBRT and nerve-sparing prostatectomy
Using previously validated models to predict 2-yr post-
treatment erectile function rates, we calculated the
expected erectile function rates according to the baseline
characteristics of each patient ). Our cohort would
have an expected potency rate (able to achieve an erection
firm enough for intercourse) of 42% (95% CI 38–45%) at 2 yr
after standard EBRT and 24% (95% CI 22–27%) at 2 yr after
nerve-sparing radical prostatectomy. This is in contrast to
the actual observed rate of 78% (95% CI 71–85%) for men in
our cohort. Vessel-sparing radiotherapy had higher erectile
function rates across all subset analyses compared to
expected potency rates for conventional EBRT and nerve-
sparing radical prostatectomy (all p < 0.001). When
analyzing only men with erections firm enough for
intercourse at baseline, 2-yr preservation of functional
erections was 87%, 69%, and 42% for vessel-sparing
radiotherapy, conventional EBRT, and nerve-sparing radical
prostatectomy, respectively ).
3.5. Subset analyses
For all physician-interrogated and patient-reported metrics
there were no consistent differences in erectile function
outcomes between patients receiving EBRT or EBRT plus
brachytherapy (Supplementary Fig. 3). By contrast, patients
who received ADT generally had worse erectile function
outcomes at 2yr andhadmoderately recoveredby5yr ).
For 93% (n = 126) of patients, the treatment plans were
able to meet all of the prespecified dose constraints to the
left and right IPA and CC (Supplementary Table 4). Only
one patient did not meet any of the dose constraints to the
bilateral IPA and CC, and this man did not have erections
firm enough for intercourse by 2 yr after treatment.
4. Discussion
Analogous to nerve-sparing radical prostatectomy, here
we present a novel functional anatomic approach to preserve
erectile function after curative intent radiotherapy that
Table 3 – Expected model-predicted probability of men having functional erections suitable for intercourse at 2 yr after treatment compared
to observed rates
Patients with Erections Suitable for Intercourse, % (95% confidence interval) p valu
Nerve-sparing prostatectomy Conventional EBRT Vessel-sparing radiotherapy
Expected Expected Observed
Total cohort 24 (22–27) 42 (38–45) 78 (71–85) <0.001
Top quartile BEF 35 (32–38) 55 (51–59) 87 (77–97) <0.001
Bottom quartile BEF 13 (8–18) 26 (21–31) 69 (55–83) <0.001
Age <65 yr 31 (28–34) 44 (40–48) 81 (72–90) <0.001
Age 65 yr 15 (13–17) 38 (33–43) 73 (61–85) <0.001
No ADT 26 (23–29) 51 (48–54) 84 (76–92) <0.001
AD 21 (18–24) 22 (19–25) 66 (52–80) <0.001
EBRT = external beam radiotherapy; BEF = baseline erectile function; ADT = androgen deprivation therapy.
a Comparison is between conventional external beam radiotherapy and vessel-sparing radiotherapy.
b ADT use is not included in the prostatectomy model so does not impact expected potency rates for surgically treated patients.
Table 2 – Erectile function outcomes
Metric Patients, n (%)
Baseline 2 yr 5 yr
Physician-reported
Erectile dysfunction
None 101 (77.1) 47 (36.7) 41 (32.3)
Mild/partial 19 (14.5) 32 (25.0) 38 (29.9)
Yes 11 (8.4) 49 (38.3) 48 (37.8)
NA 4 7 8
Sexually active
Yes 121 (92.4) 122 (95.3) 115 (90.6)
No 10 (7.6) 6 (4.7) 12 (9.4)
Not available 4 7 8
Patient-reported
Sexual aid use
No 117 (88.0 60 (46.9) 56 (44.1)
Yes 16 (12.0 68 (53.1) 71 (55.9)
Not available 2 7 8
IIEF-5 score
24–25 46 (34.1) 14 (10.4) 19 (14.1)
21–23 31 (23.0) 33 (24.4) 21 (15.6)
16–20 58 (43.0) 48 (35.6) 50 (37.0)
<16 0 (0.0) 40 (29.6) 45 (33.3)
Not available 0 0 0
Confidence to get and keep an erection
Very low 2 (1.5) 12 (8.9) 21 (15.6)
Low 11 (8.1) 26 (19.3) 23 (17.0)
Moderate 37 (27.4) 43 (31.9) 47 (34.8)
High 55 (40.7) 42 (31.1) 33 (24.4)
Very high 30 (22.2) 12 (8.9) 11 (8.1)
Not available 0 0 0
Three-tier scale
Potent without aids 108 (80.0) 61 (45.2) 47 (34.8)
Potent with aids 27 (20.0) 55 (40.7) 72 (53.3)
Impotent 0 (0.0) 19 (14.1) 16 (11.9)
Not available 0 0 0
IIEF-5 = International Index of Erectile Function questionnaire; NA = not
available.
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