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With 11,000 attendees from the
radiology community, the 2016 ASTRO
annual meeting showcased the latest
in radiation therapy techniques and
technologies. The
PracticeUpdate
Editorial Team reports from Boston
on some of the highlighted clinical
trial data presented at the meeting.
58th annual meeting of the
American Society for Radiation
Oncology (ASTRO)
median boost dose was 14 Gy. Records documenting patients
receiving a brachytherapy boost, those with unknown boost
status, and those who receive partial breast radiation were not
included in the analysis.
Among 4131 cases included in the analysis, 2661 patients
received a radiation boost and 1470 did not. Radiation boosts
were more common for patients with positive margins follow-
ing breast-conserving surgery, those with unknown oestrogen
receptor status, and individuals with documented necrosis.
Median follow-up was 9 years.
Patients with DCIS who received a radiation boost following
whole breast radiotherapy experienced a reduction in local
recurrence. Ipsilateral breast tumour-free survival for boost
versus no boost, was 97.1 versus 96.3% at 5 years, 94.1 versus
92.5% at 10 years, and 91.6 versus 88.0% at 15 years following
treatment, respectively (P = 0.013).
Dr Moran remarked, “Many radiation oncologists routinely
deliver a boost after whole breast radiotherapy for DCIS. We
anticipated a similar benefit to that of invasive cancers. But
we haven’t had consistent data to demonstrate this benefit in
DCIS.”
She continued, “Our study has demonstrated that a radiation
boost provides an albeit small but significant long-term benefit
in reducing breast tumour recurrence for patients with DCIS.
The results support consideration of a boost in patients with
DCIS who undergo whole breast radiotherapy and have life
expectancies of 10 or more years.”
The benefit in reducing in-breast recurrence was demon-
strated across all age subgroups. Furthermore, treatment with
the DCIS boost was an independent predictor of decreasing
ipsilateral breast tumour recurrence on multivariate analyses
that controlled for grade, necrosis, margin status, age, tumour
size, and tamoxifen use.
On subset analysis, though the boost did not convey a statisti-
cally significant benefit in the subset of patients with positive
margins, it did independently predict for reducing ipsilateral
breast tumour recurrence in all age groups with negative mar-
gins (all P < 0.02). Dr Moran explained that only 4% of partici-
pants comprised the subset of patients with positive margins.
It is highly likely, therefore, that the positive margin subset
was underpowered to show a statistically significant benefit.
Dr Moran stated, “Our findings suggest that adding several
additional fractions of radiation directed to the lumpectomy
cavity after whole breast radiation for DCIS provides an incre-
mental benefit in decreasing local relapse, similar in magni-
tude to the benefit of 4% at 20 years of the boost for invasive
cancers.”
“While these small numbers may not seem substantial, the
boost data in invasive disease have highlighted the clinical
importance that small decreases in local relapse provide for
patients. Ultimately, these small decreases in ipsilateral breast
tumour recurrence reduced the number of mastectomies for
recurrence by approximately 40% in patients who had received
a boost vs those who did not.”
A radiation boost
is recommended in
patients with DCIS
and ≥10 years life
expectancy following
breast-conserving
surgery and whole
breast radiotherapy
A supplemental boost of radiation has been shown
to improve local control and provide an incremen-
tal benefit in decreasing breast cancer recurrence
for patients with ductal carcinoma in situ (DCIS)
who receive whole breast radiation therapy fol-
lowing lumpectomy. This finding of a retrospective
analysis was reported at the ASTRO 2016.
M
eena Savur Moran, MD, of Yale School of Medicine,
NewHaven, Connecticut, explained that patients with
DCIS undergoing breast conservation therapy typically
receive a lumpectomy, followed by whole breast radiotherapy.
Many then receive an additional boost of radiation of four to
eight fractions to the surgical bed.
While multiple clinical trials have demonstrated a modest but
statistically significant reduction in ipsilateral breast tumour re-
currence from a radiation boost after whole breast radiotherapy
for invasive breast cancer, no phase 3 studies have evaluated
radiation boost for DCIS.
Ten academic institutions from the US, Canada, and France
provided de-identified data for 4131 cases of DCIS, the largest
cohort of patients with DCIS treated with or without boost
to date.
Eligible patients included those with pure DCIS (ie, no
microinvasion) who received whole breast radiotherapy with
or without radiation boost and reached at 5 years of follow-up.
They received either electron or photo radiation boost. The
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