S216 I. J. Radiation Oncology d Biology d Physics Volume 78, Number 3, Supplement, 2010

were 85% vs. 79%, 90% vs. 81% and 79% vs. 79%, respectively (p = NS). Loco-regional relapse occurred in one non-SSM patient,while distant failure occurred in 6 (18%) SSM patients and 18 (33%) non-SSM patients (p = 0.12). Univariate analysis demon-strated that pathCR (p = 0.03) predicted for higher overall survival.

Conclusions: This study is one of the largest series addressing outcomes and implications of SSM vs. non-SSM among womenwith locally advanced breast cancer. In our small study with limited follow-up, SSM does not appear to delay adjuvant RT, impaironcologic outcomes, nor lead to increased rates of biopsies for fat necrosis. Although surgical complication rates were significantlyhigher in SSM patients, this did not result in significant delays in adjuvant RT. Longer follow-up time is needed, but SSM appearsto be a viable option for locally advanced breast cancer patients who achieve good response to neoadjuvant chemotherapy.

Author Disclosure: R.S. Prabhu, None; K. Godette, None; R. O’Regan, None; A. Zelnak, None; C. Fasola, None; G. Carlson,None; A. Losken, None; T. Styblo, None; S. Gabram, None; M. Torres, None.

2025 Simultaneous Integrated Boost Radiotherapy for Breast Cancer: Patient Characteristics, Side Effects, and

Long Term Outcomes of Two Different Regimens

M. Torres1, M. McDonald1,2, K. Godette1, F. Andic1,3, T. Liu1, H. Liu1, D. Whitaker1, L. Davis1

1Emory University, Atlanta, GA, 2Indiana University School of Medicine, Indianapolis, IN, 3Cukurova University School ofMedicine, Adana, Turkey

Purpose/Objective(s): Recent studies support less than the traditional 6 weeks of radiotherapy (XRT) in select women with breastcancer (BRCA). We compare two different fractionation schemes using simultaneous integrated boost (SIB) XRT in a 5.5 vs. 5week period.

Materials/Methods: We reviewed the records of 455 Stage I-III consecutive BRCA patients (pts) treated with SIB XRT followingbreast preserving surgery from 9/2001 to 12/2008. 45 Gy (1.8 Gy per fraction [fxn]) was delivered to the whole breast while 60 Gywas delivered to the lumpectomy cavity. In 345 pts (SIB28), 2.14 Gy per fxn was delivered to the cavity simultaneously during 5weeks of whole breast XRT followed by 3 additional fxns of 2.14 Gy to the cavity alone (28 total fxns). In 110 pts (SIB25), 2.4 Gyper fxn was delivered to the cavity concurrently during whole breast XRT for 5 weeks (25 total fxns).

Results: The median follow-up period for SIB28 was significantly longer than for SIB25 pts (50 months vs. 26 months, respec-tively; p = 0.02). In both groups, most pts were white (57% SIB28 vs. 71% SIB25; p = 0.01), over age 40 (92% SIB28 vs. 92%SIB25), postmenopausal (68% SIB28 vs. 67% SIB25), and had BMI .24 (79% SIB28 vs. 73% SIB25). The majority had stage 0 orI disease (70% SIB28 vs. 69% SIB25), node negative tumors (80% SIB28 vs. 73% SIB25), and invasive carcinoma (79% SIB28 vs.77% SIB25) which was estrogen receptor positive (72% SIB28 vs. 78% SIB25) and Her2 negative (79% SIB28 vs. 81% SIB25)(p . 0.05 for all comparisons). There were no significant differences in margin status (negative in 83% vs. 86%) or use of che-motherapy (47% vs. 46%) and hormone therapy (66% vs. 69%) between SIB28 and SIB25 groups, respectively. SIB25 pts hadsignificantly greater median medial-lateral (ML) and anterior-posterior (AP) breast separation than SIB28 pts: ML 16.4 vs. 16.1cm (p = 0.02) and AP 11.6 vs. 11.3 cm (p = 0.04). SIB25 pts also had significantly larger breast volumes treated with XRT (Median847.4 cm3 vs. 742.6 cm3, p = 0.01). Despite having larger breasts and receiving higher daily cavity dose, SIB25 pts had significantlylower rates of grade 2 or higher acute skin toxicity than SIB28 pts (23% vs. 41%, respectively p = 0.01). On multivariate analysis,treatment with 28 fxns (p = 0.001) and larger breast volumes (p = 0.001) predicted for worse acute skin toxicity. Among womenwith invasive BRCA, there was no difference in local control (95% SIB28 vs. 97% SIB25), distant metastasis free survival (94%SIB28 vs. 97% SIB25, or overall survival (96% SIB28 vs. 89% SIB25) at 4 years. Among DCIS pts, there was also no difference inoutcome based on SIB regimen.

Conclusions: Our data supports the use of a 5 week SIB regimen in select pts and suggests that larger breast size may not be a con-traindication to hypofractionation techniques. Randomized studies are warranted to investigate this further.

Author Disclosure: M. Torres, None; M. McDonald, None; K. Godette, None; F. Andic, None; T. Liu, None; H. Liu, None; D.Whitaker, None; L. Davis, None.

2026 A Rapid Automated Process for Selection of Breath Hold Technique via Active Breathing Control to

Achieve Cardiac Dose Reduction among Patients Receiving Left Sided Breast Irradiation

W. Wang, T. G. Purdie, M. Rahman, A. Marshall, A. Fyles

Department of Radiation Oncology, Princess Margaret Hospital, Toronto, ON, Canada

Purpose/Objective(s): To use a rapid automated planning process for the selection of patients for moderate deep inspiration breathhold (mDIBH) technique. ii) To evaluate the dose reduction to the left anterior descending artery (LAD) and the heart by mDIBHtechnique via active breathing control (ABC) for left-sided breast irradiation.

Materials/Methods: Between Nov 2009 and Mar 2010, 39 patients underwent left-sided breast irradiation with two-field tangen-tial intensity modulated radiation therapy (IMRT). Automated plan were generated for cardiac dose assessment. All patients withunfavorable cardiac anatomy, defined as having more than 10cc of heart receiving 50% of the prescribed dose on the free breathing(FB) plans, were treated on a protocol using mDIBH technique via ABC. The dose to the LAD and the heart were compared be-tween FB and mDIBH plans using paired t-test.

Results: Tangential breast IMRT plans were generated by an automated planning process requiring approximately 9 minutes forplanning and QA. Based on the dose to the heart in the FB plans, 17 of the 39 patients screened were selected for ABC (42.4 Gy in16 fractions in 16 patients, and 50 Gy in 25 fractions in 1 patient). The mean volume of the heart receiving 50% of prescribed dosewas 30.7 cc on the FB plans, and 3.7 cc on the mDIBH plans, a reduction of 88% (p \ 0.001). The mean dose to the heart wasreduced from a mean of 318.0 cGy on FB plans, to 131.2 cGy on mDIBH plans, a reduction of 59% (p\0.001). The median lengthof LAD within the radiation field was reduced from 6cm (range, 4-10 cm) on the FB plans, to 0 cm (range, 0-4 cm) on the mDIBHplans. The mean dose to LAD was reduced from a mean of 1946.4 cGy on FB plans, to 548.5 cGy on mDIBH plans, a reduction of72% (p\0.001). The maximum dose to 0.2 cc of LAD, equivalent to approximately 1 cm in length, was reduced from a mean of