Scientific Abstract 2126; Table

T1a/b T1c T2 T3

Luminal A 9.4% (n Z 76/808) 26.6% (n Z 328/1232) 47.1% (n Z 395/839) 66.7% (n Z 72/108)Luminal B 2.5% (n Z 1/40) 20.6% (n Z 21/102) 44.9% (n Z 35/78) 92.3% (n Z 12/13)HER 2 0.0% (n Z 0/14) 33.3% (n Z 5/15) 47.6% (n Z 10/21) 100% (n Z 4/4)Basal 6.4% (n Z 2/31) 26.0% (n Z 19/73) 40.0% (n Z 30/75) 76.9% (n Z 10/13)

International Journal of Radiation Oncology � Biology � PhysicsS268

metastasis for each combination of molecular subtype and T-stage. For the

Luminal A subtype, there was no significant difference in the incidence of

LN metastasis according to the PR status (p Z 0.228). Independent sta-

tistically significant (p < 0.05) predictors of LN metastasis included T-

stage, younger age, and number of nodes evaluated, whereas statistically

significant predictors of advanced nodal stage included T-stage, grade,

number of nodes evaluated.

Conclusions: Molecular subtype does not independently predict for nodal

involvement or advanced nodal stage in breast cancer. Instead, T-stage,

tumor grade, patient age, and number of nodes evaluated may be the most

relevant factors in guiding regional management considerations.

Author Disclosure: J.K. Bhatia: None. D. Metzger: None.H. Ashamalla:

None. E. Katsoulakis: None. M.D. Mattes: None.

2127Postmastectomy Chest Wall Radiation of Left-Sided Breast CancerPatients With Single Energy Electron Beam Versus 3-DimensionalConformal Radiation Therapy With Photons: Analysis of DosimetricParametersA. Kesava Ramgopal, H. Mahendran, T. Deepa, S. Uma Rajeswari,

D. Anbalagan, J. Kumar Reddy, R. Ramesh Babu, G.V. Satheesh Kumar,

T.V. Basava Sankara Rao, V. Sivanageswara Rao, and M. Gopichand; HCG

Curie City Cancer Centre, Vijayawada, India

Purpose/Objective(s): Post mastectomy chest wall radiation is routinely

delivered using tangential photon fields. However for left sided tumors

underlying heart and left lung form major organs at risk and this report

studies the use of single energy electron-beam radiation therapy in these

patients. The aim of this study is to compare mean left lung dose, per-

centage volume of left lung receiving dose more than 20 Gy (V20 Gy),

mean heart dose, percentage volume of heart receiving dose more than 25

Gy (V25 Gy) and 45 Gy (V45 Gy), percentage volume of planned target

volume (PTV) receiving more than 95% of prescribed dose (V95%).

Materials/Methods: Twenty left sided breast cancer patients who under-

went modified radical mastectomy and required postmastectomy chest wall

radiation were included in this study. Patients were immobilized in a ther-

moplastic mold and simulation was done using spiral CT scan with 4 mm

thick slices. Images were transferred to a planning system and contouring of

target volumes and organs at risk was done according to standard guidelines.

Three dimensional conformal radiation therapy plans were generated using

6MV medial and lateral tangential beams with paired wedges and 0.5 cm

bolus, multileaf collimators were used to shape the beams. Electron-beam

plans were generated with a single anterior oblique beam of 12MeVand 0.5

cm bolus. A dose of 50 Gy was prescribed to PTV in 2 Gy per fraction, 25

fractions. Dose plans were evaluated and data analysis was done using

Windows SPSS software for Statistical analysis version 20.

Results: There was significant difference in favor of electron-beam plans

for mean lung dose (pZ 0.001), V20 Gy of left lung (pZ 0.001) and V45

Gy of heart (pZ 0.017). There was no significant difference in mean heart

dose (p Z 0.624) and V25 Gy of heart (0.622). The difference in

percentage volume of PTV receiving more than 95% of prescribed dose

(p Z 0.077) showed trend towards significance.

Conclusions: Single energy electron-beam therapy can significantly reduce

doses to heart and left lung in postmastectomy radiation therapy of left

sided breast tumors with appropriate patient selection when compared to

conformal radiation using photons.

Author Disclosure: A. Kesava Ramgopal: None. H. Mahendran: None.

T. Deepa: None. S. Uma Rajeswari: None. D. Anbalagan: None. J.

Kumar Reddy: None. R. Ramesh Babu: None. G.V. Satheesh Kumar:

None. T.V. Basava Sankara Rao: None. V. Sivanageswara Rao: None.

M. Gopichand: None.

2128Association Between Breast Cancer and Glioblastoma Multiforme inWomen: A California Cancer Registry Population-Based AnalysisR.L. Wei,1,2 A. Ziogas,3 P. Daroui,1,2 and C. Nangia1,2; 1University of

California Irvine, Orange, CA, 2Chao Comprehensive Cancer Center,

Orange, CA, 3University of California Irvine, Irvine, CA

Purpose/Objective(s): Reports of a relationship between breast cancer

patients subsequently developing glioblastoma multiforme (GBM) have

been reported in the literature, however there are no published analytical

studies addressing this association. This current study is a population-

based, retrospective cohort analysis that evaluated the risk of developing

GBM in women who were diagnosed with breast carcinoma.

Materials/Methods: We analyzed data on 390,429 women from the Cal-

ifornia Cancer Registry whose first cancer was either invasive or in-situ

breast cancer, diagnosed from 1988 through 2009, yielding 339 subsequent

diagnosed GBMs. Standardized incidence ratios (SIR) with 95% confi-

dence intervals (CIs) were used to evaluate risk of GBM, accounting for

age at first diagnosis with breast cancer, duration at risk, and race/ethnicity.

Results: 339 women diagnosed with an invasive GBM with a median age

at diagnosis of GBM of 69 years old and median time between diagnosis of

breast cancer and GBM of 5 years (range 1-22). Women diagnosed at an

early stage breast cancer, diagnosed with breast cancer at older ages, White

Non-Hispanic, and ER positive were more likely to develop GBM A

moderately increased SIR of GBM was found among women diagnosed

with breast carcinoma, with an SIR of 1.16 (95% confidence interval [95%

CI], 1.04-1.29). The SIR was 1.41 (95% CI Z 1.01 - 1.92) in woman who

developed breast carcinoma prior to menopause (�45 years old). Women

who were not on hormonal blockade had higher (SIR 1.19, 95%

CI Z 1.05-1.36) risk than patients that were on hormonal blockade (RR

1.07, CI 0.87-1.31). Women who did not underwent radiation therapy

(RR 1.21, 95% CI Z 1.05-1.39), and/or did not undergo chemotherapy

(RR 1.23, 95% CIZ 1.08-1.39) had a higher risk of GBM development. In

addition, women with localized disease were more likely to develop GBM

(SIR 1.25, 95% CI Z 1.09-1.43) as well as women with estrogen receptor

positive tumors (SIR 1.17, 95% CI Z 1.00-1.37).

Conclusions: This is the first study demonstrating a statistically significant

association between breast cancer and subsequent development of GBM.

These results suggest that the risk of developing GBM among women with

breast cancer is elevated moderately relative to their peers, but that the risk

is substantially elevated in women who develop breast cancer before the

age of 45, when the level of estrogen is presumed to be higher before

menopause. This preliminary population based data lends support to

research showing estrogen receptor markers that link hormonal pathway

with GBM formation and/or progression. Further studies are needed to

determine specific molecular pathways that may be associated with this

clinical association.

Author Disclosure: R.L. Wei: None. A. Ziogas: None. P. Daroui: None.

C. Nangia: None.

2129Outcomes for APBI With Strut-Based Brachytherapy: First 200Accrued Patients (52-Month Median Follow-Up)C.M. Yashar,1 D. Scanderbeg,1 C.A. Quiet,2 M.B. Snyder,2 M. Lyden,3

D. Attai,4 L.T. Komarnicky,5 J. Reiff,5 S.S. Nigh,6 J. Pollock,7 E. Butler,7