One-week ultrahypofractionated RT for whole breast and simultaneous integrated boost in DCIS
PO-1143
Abstract
One-week ultrahypofractionated RT for whole breast and simultaneous integrated boost in DCIS
Authors: Raquel Ciervide1, Angel Montero1, Mariola Garcia-Aranda1, Beatriz Alvarez1, Alejandro Prado2, Xin Chen-Zhaoi1, Rosa Alonso1, Mercedes Lopez1, Ovidio Hernando1, Emilio Sanchez1, Jeannette Valero1, Monica Nuñez1, Marta Izquierdo1, Karla Rossi1, Carmen Cañadillas1, Jaime Marti1, Daniel Zucca1, Leire Alonso1, Pedro Fernandez-Leton1, Carmen Rubio1
1HM Hospitales, Radiation Oncology, Madrid, Spain; 2HM Hospitales, Radiation Oncology, Madrid, Spain
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Purpose or Objective
Whole breast irradiation (WBI)
after breast conserving surgery (BCS) is indicated to improve loco-regional
control and survival in ductal carcinoma in situ (DCIS). Former studies showed benefit of tumor bed boost irradiation in local
control. Hypofractioned regimens in 3 weeks are considered standard radiation
therapy although recent studies have shown the non-inferiority of a treatment
regimen of 5 fractions in one week in ductal carcinoma in situ. We present our
preliminary results of feasibility and tolerance of a ultra-hypofractionated 5
fractions in one-week WBI schedule with simultaneous integrated boost (SIB) in DCIS.
Material and Methods
From April 2020 to January-2021,
29 patients with a median age of 55 years (range 42-76) and histological
diagnoses of DCIS were treated according to our institution ultra-hypofractionated
radiotherapy schedule after breast conserving surgery.
Radiotherapy comprises the whole
breast receiving 26Gy of 5.2Gy/fraction and simultaneous integrated boost (SIB) was
administered to all patients up to a total dose of 29Gy of 5.8Gy/fraction in 25p (86%) and
30Gy of 6Gy/fraction in 4p (14%) with close/focally affected margins. WBI+SIB was delivered
by conformal 3-D technique in 28p (96.5%) and VMAT in 1p (3.5%). Treatment beam arrangement for SIB comprised of
coplanar beams: 3 beams in 11p (38.5%), 4 beams in 14p (48%), 5 beams in 3p (10%) and
2 arcs in 1p (3.5%). Dose constraints are detailed in table 1. 26p (90%) received adjuvant hormone therapy
Table 1. Dose constraints
|
Organ at risk
|
|
|
|
Ipsilateral lung
|
V12<20% (if only Breast
+/-boost)
|
Inhouse constraint
|
|
Contralateral lung
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Average Dose <5.6 Gy
|
RTOG 1005
|
|
V3.6 <10%
|
RTOG 1005
|
|
Heart
|
V12 <5%
|
Inhouse constraint
|
|
V7<5%
|
FAST-FORWARD
|
|
V1.5 < 30% (if only
breast + boost)
|
FAST-FORWARD
|
|
Contralateral Breast
|
V3.6 < 30 %
|
|
|
Spinal Canal
|
Max Dose < 27 Gy
D0.01 cc< 22.5 Gy
|
Inhouse constraint
|
Results
With a median follow-up of 3
months (range 1-10), tolerance was acceptable with null o mild toxicity: 17p (59%)
developed skin toxicity grade 1. No toxicities ≥grade 2 were reported.
A comparative analysis was calculated
with Chi-Square test. We found a significant relation between PTV breast volume
(>750cc) and dermitis G1-2 (P: 0.03),
however analysis didn´t show any relation between the age (p: 0.14), the use
of hormonotherapy (p: 0.43), dose to PTV boost (p: 0.2), PTV Boost Volume (P:
0.31) or ratio PTV Boost/PTV Breast (P: 0.43) and tolerance.
Conclusion
Ultra-hypofractionated whole breast irradiation with simultateous integrated boost in 5 fractions along one-week is feasible and well tolerated in DCIS although
longer follow-up is neccessary to confirm these results.