Akademik Veri Yönetim Sistemi
GEC-ESTRO-ISIORT Europe Conference 30th Anniversary, London, İngiltere, 7 - 10 Mayıs 2011, cilt.99, sa.1, ss.252
Purpose: The addition of a tumor bed boost after whole breast radiotherapy
(WBRT) has been shown to improve local control in breast cancer patients.
Boost plans generated with photons or electrons usually result in inhomoge
neous dose distributions within the tumor bed while increasing the doses in
breast volume. Breast brachytherapy (BT) might provide a better homogene
ity within the tumor bed while reducing the dose in the breast tissue. In this
study, we aimed to compare dose-volume histograms of conformal external
radiotherapy plans with high dose rate (HDR) BT.
Materials: Four patients pathologically diagnosed with breast cancer under
went breast conserving surgery received WBRT followed by BT boost at our
institution. Boost plans were initially tailored with 16MeV electron beams for
3 of the patients and 18MV for 1 patient with ECLIPSE version 8.6 (Varian
Palo Alto USA) radiotherapy planning system, three dimensional conformal
planning was done to obtain dose- volume information. Boost plans were
summed up with WBRT plans in order to evaluate the dose distributions.
Given the large irradiated volumes and hot spots inside the breast tissue,
these patients were found to be candidates for BT boost. BT plans were gen
erated via ECLIPSE BrachyVision treatment planning system and treatments
were applied with Varisource 200 HDR (Ir-192 source). Plastic catheters were
placed in the breast depending on the location size and shape of the tumor
bed and geometrically adjusted in order to cover the tumor bed with the help
of a guiding template, under general anesthesia. The catheters were mea
sured through the transfer cables connecting to the source. All patients were
scanned with a multi-detector 16 slice CT (Siemens sensation 16 Erlangen,
Germany) with 3mm interval. Images were transferred as DICOM III format
via network between CT and ECLIPSE. The catheters were contoured and
their positions within the breast were defined. Target volumes and organs at
risk (OAR) were delineated. Source lengths and their locations in the trans
fer cable were illustrated depending on the tumor size. Dose distribution was
manually optimized in order to achieve adequate tumor bed coverage. The
implantation and dose specifications were performed similar to the rules of
the Paris system. The minimum central dose (MCD) was defined by calcu
lating the mean of basal doses while minimum peripheral dose (MPD) was
defined by calculating the 85% of mean basal dose. The total HDR boost
dose of 15Gy was delivered in 5 fractions of 3Gy MPD, two fractions a day, 8
hours apart.
Results: Table1 summarizes the data for 4 cases including the MCD, MPD
and homogeneity index (HI) parameters. D90 is the dose received by the 90%
of the volume, V100, V90 and V50 describe the volumes receiving the 100%,
90% and 50% of the prescription dose, respectively. Lung dose changes
depending on the treatment technique are shown in table2