Stereotactic
body
radiotherapy
(SBRT)
for
localized
prostate
cancer
did
not
improve
urinary
irritation
or
disease-free-survival
(DFS)
compared
with
hypofractionated
intensity-modulated
radiotherapy
(IMRT),
a
large
randomized
trial
showed.

After
a
median
follow-up
of
3.2
years,
the
frequency
of
urinary-irritative
symptoms
was
35.4%
with
SBRT
and
33.7%
with
IMRT,
although
the
incidence
of
several
other
urinary
and
bowel
symptoms
was
improved
at
various
time
points.
The
DFS
at
3
years
favored
moderately
hypofractionated
IMRT,
92.1%
versus
88.6%.

The
rate
of
prostate
specific
antigen
(PSA)
failure
did
not
differ
between
the
two
groups,
reported
Rodney
J.
Ellis,
MD,
of
the
University
of
South
Florida
in
Tampa,
and
colleagues
in


JAMA.

“This
study
has
immediate
impact
on
patients
and
physicians
considering
a
shorter
course
of
radiotherapy
for
localized
prostate
cancer,”
the
authors
stated.
“Furthermore,
there
are
several
important
insights
drawn
when
this
study
is
placed
in
the
context
of
prior
randomized
studies
investigating
SBRT
for
prostate
cancer.
The
DFS
is
numerically
worse
for
SBRT
…
so
it
remains
possible
that
improved
freedom
from
adverse
quality-of-life
effects
may
come
at
the
price
of
worse
DFS
should
this
difference
become
statistically
significant
with
further
follow-up.”

Beyond
the
actual
results,
the
study
offers
some
broader
lessons
for
the
future
of
prostate
radiation
therapy
(RT),
according
to
the
authors
of
an

accompanying
editorial.
The
trial
reinforces
the
importance
of
radiation
dose
in
determining
biochemical
control,
so
a
logical
next
step
for
SBRT
would
be
to
evaluate
ways
to
escalate
dose
while
maintaining
acceptable
toxicity,
wrote
Stanley
L.
Liauw,
MD,
of
the
University
of
Chicago,
and
W.
Robert
Lee,
MD,
of
Duke
University
Medical
Center
in
Durham,
North
Carolina.

Second,
the
“narrow
separation”
between
tumor
control
and
complications
suggests
the
importance
of
factors
beyond
radiation
dose,
they
continued.
Treatment
margins
and
motion
management
might
play
a
key
role.

“Ultimately,
the
most
important
message
…
may
be
that
optimizing
prostate
cancer
outcomes
requires
attention
to
a
constellation
of
treatment
parameters
rather
than
a
singular
focus
on
fractionation
schedule,”
Liauw
and
Lee
concluded.
“Longer
follow-up
of
this
study
will
be
important
to
better
understand
the
differences
observed
between
SBRT
and
MH
[moderately
hypofractionated]-IMRT
at
this
relatively
early
time
point.
…
As
radiation
therapy
for
prostate
cancer
continues
to
evolve,
the
lessons
from
[this
trial]
will
help
guide
the
next
generation
of
innovation.”

The

NRG-GU005
trial
had
its
origin
in
the
recognition
that
the
time
demands
and
toxicity
of
radiation
therapy
impact
patients,
caregivers,
and
“entire
healthcare
systems,”
Ellis
and
colleagues
noted
in
their
introduction.

To
address
those
issues,
investigators
at
136
centers
in
Asia,
Canada,
Europe,
and
the
United
States
randomized
698
patients
with
newly
diagnosed
intermediate-risk
prostate
cancer
to
SBRT
(36.25
Gy
in
five
fractions)
or
IMRT
(70
Gy
in
28
fractions
or
60
Gy
in
20
fractions).
The
primary
outcomes
were
the
frequency
of
a
minimally
clinically
important
decline
(MCID)
in
urinary-irritative/obstructive
and
bowel
symptoms
at
2
years
and
DFS
at
3
years.

Previously,
the

PACE-B
trial
showed
that
SBRT
and
conventional
RT
had
similar
clinical/biochemical
failure
rates
in
men
with
intermediate-risk
localized
prostate
cancer.

The
report
from
NRG-GU005
showed
no
significant
difference
in
the
urinary-irritative
domain
of
the

Expanded
Prostate
Cancer
Index
Composite-26
(EPIC)
questionnaire
(P=0.68)
after
2
years.
The
DFS
advantage
for
IMRT
at
3
years
met
statistical
criteria
for
rejecting
the
alternative
hypothesis
favoring
SBRT
(P<0.001).

Analysis
of
secondary
endpoints
showed
less
urinary
incontinence
after
1
and
2
years
and
better
sexual
function
at
1
year
in
the
SBRT
arm.
Significantly
fewer
grade
3/4
genitourinary
adverse
events
occurred
with
SBRT
(0.6%
vs
2.5%,

P=0.04),
and
a
significantly
lower
incidence
of
MCIDs
in
the
bowel
domain
of
the
EPIC-26
(34.9%
vs
43.8%,

P=0.03).

“This
study
provides
an
important
advance
in
the
understanding
of
the
radiotherapeutic
treatment
of
prostate
cancer,”
the
authors
stated.
“SBRT
is
more
convenient
and
less
expensive
than
conventionally
fractioned
radiation.
While
SBRT
requires
fewer
treatments,
it
is
a
more
complex
technology
and
requires
more
staff
effort
and
physician
oversight.
Recently

proposed
legislation
in
the
U.S.
attempts
to
provide
reimbursement
regardless
of
treatment
fractionation,
encouraging
physicians
to
choose
the
treatment
they
believe
is
best
without
potentially
conflicting
reimbursement
incentives.”

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