Abril - 2017

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Brachytherapy guideline in prostate cancer (high and low dose rate)
Rev Assoc Med B ras 2017; 63(4):293-298 295
Amedical literature review study18 selected only articles
involving all therapeutic modalities for localized and strat-
ified prostate cancer, per risk group, that had at least 100
patients and 5 years of follow-up between 2000 and 2010.
Out of 18,000 selected studies, 848 met the above criteria.
Of these, 3% involved high-intensity focused ultrasound
(HiFU), 5% involved robotic prostatectomy, 9% involved
open radical prostatectomy, 15% involved proton external
beam RT, 16% involved cryotherapy, 18% involved photon
external beam RT and 31% involved BT (both modalities).
Over 50,000 patients were assessed. In the comparison of
outcomes (mainly PSA progression-free survival), BT pre-
sented results similar to those of surgery and external beam
RT for low- andmoderate-risk patients, but not for high-risk
patients who benefited from combination therapies (B).
The American Society of Brachytherapy19 and the
American Urological Association20 indicate that the best
candidates to undergo prostate BT are patients at low risk
for the disease (B). Remarks should be made for patients
with moderate-risk prostate cancer, since within this group
there are individuals with a favorable prognosis and who
could possibly be treated with BT as well. Patients with
low disease volume characteristics (total biopsy tissue
invaded by tumor < 50%), predominant Gleason 3 pattern
(3+4 and not 4+3) and absence of perineural invasion
would be the candidates to receive monotherapy with BT.
Is high dose-rate brachytherapy an equally
effective option as monotherapy?
There is no formal comparison in clinical studies between
HDR-BT and other modalities.
A US Phase 2 study21 involved 110 patients with low-
and moderate-risk tumors for treatment with HDR-BT
as monotherapy (three dose types were used: 34 Gy in
four fractions, 36 Gy in four fractions and 31,5 Gy in three
fractions with intervals of 6 hours between them). Hor-
mone replacement therapy was allowed. Acute toxicities
observed were relatively high, but there was no biochem-
ical recurrence after 30 months of median follow-up (C).
A single-center retrospective study22 included 77 pa-
tients treated with HDR-BT as monotherapy (three im-
plants with a dose of 15 Gy each every 3 weeks). Hormone
replacement was allowed for patients with high-risk tu-
mors. At a median follow-up of 57 months, overall sur-
vival, biochemical control and local control were 98.7%,
96.7% and 96.9%, respectively (C).
A single-center retrospective study23 involved 351
patients also treated with HDR-BT as monotherapy (four
fractions of 9.5 Gy with a 14-day interval between them),
but only patients with low-risk tumors were included
and hormone replacement was not allowed. At a 5-year
follow-up, biochemical control and metastasis-free sur-
vival were respectively 99% and 98% (C).
The American Society of Brachytherapy specifically
recommends for the indication of HDR-BT24 that the
procedure be performed only in low- or moderate-risk
patients as monotherapy, on an investigational basis (B).
Is low dose-rate brachytherapy an equally
effective option as boost after external
beam RT?
There is some evidence based on observational series and
randomized studies, but without a direct comparison.
The RTOG 001925 is a phase 2 study that included
138 patients predominantly at moderate risk for treatment
with external beam RT (45 Gy prescription dose) targeting
the prostate and seminal vesicles, followed by a LDR-BT
boost (108 Gy prescription dose). After 48 months of
median follow-up, the observed rate of biochemical fail-
ure was 14% (B).
A single center observational study26 showed the follow-
up of 223 patients with T1 and T3 stages treated with ex-
ternal beam RT (45 Gy) followed by LDR-BT (I-125 or Pd-
103). After 15 years of follow-up, PSA failure-free survival
was 74% for the entire sample. Classified according to risk
groups, patients with low, moderate and high risk pre-
sented 85.8%, 80.3% and 67.8%, respectively (p=0.002) (C).
Is high dose-rate brachytherapy an equally
effective option as boost after external
beam RT?
Some studies have analyzed the strategy of irradiation
dose escalation with HDR-BT after external beam RT in
patients preferably at moderate risk.
A randomized study from the UK analyzed 220 patients
(T1 to T3 without metastases, PSA < 50 ng/mL) treated
with external beam RT alone (55 Gy in 20 fractions) versus
external beam RT (35.7 Gy in 13 fractions) followed by
HDR-BT boost (two implants with 24h interval and 8.5
Gy prescribed dose per implant). Mean PSA failure-free
survival was 4.3 versus 5.1 years (p=0.03). Acute rectal
toxicity was favorably attributed to the HDR-BT group:
lower rate of grade II proctitis (14% versus 5%, p=0.025).
Other toxicity indicators were similar (A).
A prospective US multicenter study 27 analyzed 207
patients (T2b, Gleason ≥ 7, PSA ≥ 10 ng/mL) treated with
external beam RT (46 Gy) and HDR-BT, using two im-
plants (first and third weeks of external beam RT) with
doses between 5.5 and 11 Gy per implant. After a median
follow-up of 4.7 years, biochemical control was at 74% for