The Role of Hormone Therapy for Node Negative Breast Cancer Patients With ER + Tumors 1 cm or Less

S248

International Journal of Radiation Oncology  Biology  Physics

Purpose/Objective(s): Recent studies have shown applications of conventional parallel-hole SPECT and single-pinhole SPECT in imaging the axillary region in association with breast cancer treatment. One application has been to image with 99mTc sulfur colloid in order to identify lymph nodes primarily responsible for arm lymphatic drainage. Lymphedema is a prominent morbidity in breast cancer treatment. This non-curable disease can be caused by axillary lymph node dissection (ALND), sentinel lymph node biopsy (SLNB), and radiation therapy, which may damage the axillary lymph nodes that drain the arm. In radiation therapy, such SPECT imaging may enable adjustments to the treatment plan to reduce dose to these nodes. Another SPECT application has been to detect metastases to lymph nodes using 99mTc Tetrofosmin and 99mTc MIBI. However, current SPECT systems have limited image resolution and sensitivity, and no SPECT systems have been implemented to acquire functional and molecular information when the patient is on the treatment table. Therefore, we propose onboard robotic multi-pinhole SPECT for imaging the axilla. This system can provide improved SPECT resolution and sensitivity within a target region about the axilla, and it enables SPECT imaging while the patient is in position for radiation therapy. Materials/Methods: Radiotracer fine structure was computer-simulated in the axillary region of a torso phantom that otherwise contained a uniform background activity. Based on this phantom, SPECT projection data were computer-simulated for a multi-pinhole SPECT system and for a reference parallel-hole collimated detector. Trajectories of the multi-pinhole and parallel-hole collimated systems were designed to image a small target region encompassing the fine structure. Noisy Poisson-distributed projection data were drawn from these simulated projections, and SPECT images were reconstructed by OSEM. A robot is proposed for maneuvering the SPECT detector system about patients in position for radiation therapy. Commercial CAD programs were utilized to evaluate the feasibility of robot and detector trajectories about the patient/axilla, treatment table, and linear accelerator gantry. Results: The multi-pinhole SPECT system resolves much of the fine structure in the axilla, whereas this fine structure is unresolved with the parallel-hole collimated detector. The CAD simulations demonstrate that robot and detector trajectories about patients in position for radiation therapy are feasible. Conclusion: Robotic multi-pinhole SPECT shows promise for targeted imaging of the axillary region as patients are in position for radiation therapy. Author Disclosure: S. Yan: None. J. Bowsher: None. F. Yin: None.

up and at yearly intervals using the Harvard Scale (E/G/F/P). Dosimetry parameters were evaluated for association with cosmesis outcomes. Results: For the early follow up period, 260 breasts were evaluated with 97.3% having excellent or good grades. Skin spacing was the only variable correlating significantly with cosmesis. Skin spacing for the E/ G group and F/P group were 14.2 +/- 13.6mm and 6.0 +/- 4.8mm (p Z 0.045). Cosmesis was E/G in 83% and 89% of patients with skin spacing of <3mm and 3-5mm, respectively. For all other variables, no clinically significant correlations were found. For the 1-year follow up period, 301 breasts were evaluated with 93.0% having excellent or good grades. Skin spacing was the only variable correlating significantly with cosmesis. Skin spacing for the E/G group and F/P group were 13.7 +/12.7mm and 8.2 +/- 6.1mm (p Z 0.042). Cosmesis was E/G in 82% and 84% of patients with skin spacing of <3mm and 3-5mm, respectively. For all other variables, no clinically significant correlations were found. For the 2-year follow up period, 146 breasts were evaluated with 91.1% having excellent or good grades. No variable correlated statistically with cosmesis (all p > 0.10). Skin spacing, although not significant (p Z 0.115), for the E/G group and F/P groups were 12.1 +/10.2mm and 7.5 +/- 4.9mm. Cosmesis was E/G in 89% and 80% of patients with skin spacing of <3mm and 3-5mm, respectively. For all three follow up time periods, device size (largest was 10-1, smallest was 6-1mini) was not correlated with cosmesis (<1-yr, p Z 0.63; 1-yr, p Z 0.97; 2-yr, p Z 0.95). Conclusions: The SAVI applicator provided excellent or good cosmetic outcomes in greater than 90% of patients. Skin spacing was weakly correlated with outcome at early follow up. Even in anatomically challenging cases (skin bridge <3mm and 3-5mm), cosmetic outcomes were excellent/good in 80-90% of patients at these follow up intervals. Author Disclosure: S.E. Finkelstein: None. R.L. Hong: F. Honoraria; Cianna Medical. L. Komarnicky-Kocher: None. R.R. Kuske: None. L. Liu: None. M. Lyden: B. Independent Contractor; Cianna Medical. R.R. Patel: F. Honoraria; Cianna Medical. C.A. Mantz: None. K.J. McClain: None. C. Yashar: F. Honoraria; Cianna Medical.

2078

Purpose/Objective(s): The use of screening mammography has increased the incidence of breast cancer that is 1cm or less. There is some uncertainty regarding the adjuvant systemic treatment for these node negative small tumors. For patients with ER + tumors that are less than 1cm, tamoxifen (TF) has been shown to decrease local recurrence and contralateral breast cancer. It is standard therapy to administer aromatase inhibitors (AIs) to postmenopausal women and TF to premenopausal women. However, the impact of AIs on clinical outcome has not been well studied for small ER+ tumors. We evaluated the clinical impact of two types of endocrine therapy including a large number of patients receiving AIs compared to TF or observation. Materials/Methods: Medical records of consecutively treated node negative, ER + patients with tumors 1cm or less receiving adjuvant radiation after breast conserving surgery between 1/95 and 7/11 were reviewed. Univariate Cox regression models were fitted to identify the significant predictors of overall survival (OS) and progression-free survival (PFS) regarding hormone therapy (HT). Wald chi-squared test derived from Cox models for testing HR were used. Results: Median follow-up was 43.5 months for 210 patients. HT patients were similar in age, menopause status, race, axillary lymph node number, p-size, follow-up time and RT dose when compared with non-HT patients. HT patients were more likely to be pT1b (46% vs 64%, p Z 0.043). Out of 171 patients receiving HT, 95 patients received AIs and 76 patients received TF. When AI patients were compared with TF patients, there were

Dosimetric Variables Correlating With Excellent and Good Cosmetic Outcomes in a Large, Retrospective Study of APBI With a Strutbased Breast Brachytherapy Applicator S.E. Finkelstein,1 R.L. Hong,2 L. Komarnicky-Kocher,3 R.R. Kuske,4 L. Liu,1 M. Lyden,5 R.R. Patel,6 C.A. Mantz,7 K.J. McClain,1 and C. Yashar8; 121st Century Oncology Translational Research Consortium (TRC), Scottsdale, AZ, 2Virginia Hospital Center, Arlington, VA, 3Drexel University College of Medicine, Philadelphia, PA, 4Arizona Breast Cancer Specialists, Phoenix, AZ, 5BioStat International, Tampa, FL, 6Western Radiation Oncology, Mountain View, CA, 721st Century Oncology TRC, Fort Myers, FL, 8University of California San Diego, San Diego, CA Purpose/Objective(s): The SAVI Collaborative Research Group (SCRG) is a coalition of 14 institutions who have retrospectively compiled a large database of APBI patients treat with the SAVI breast brachytherapy applicator. This report details the findings of statistical correlations between numerous dosimetry variables and cosmetic outcome. Materials/Methods: The SCRG database is a retrospective compilation of 1010 treated with the SAVI applicator. Dosimetry parameters were recorded for patients, including: V90, V95, V100, V150, V200, skin spacing, maximum skin dose, tumor size, PTV_Eval, and SAVI size (model). Cosmesis was graded by physicians at early (<1 yr) follow

2079 The Role of Hormone Therapy for Node Negative Breast Cancer Patients With ER + Tumors 1 cm or Less J.E. Panoff, T. Koru-Sengul, F. Miao, V. Gunaseelan, J. Wright, and C. Takita; University of Miami Leonard Miller School of Medicine, Miami, FL

Volume 84  Number 3S  Supplement 2012 significant differences in age (AI Z 60, TF Z 53, p < 0.0001), p-size (AI Z 0.68, TF Z 0.56, p Z 0.02), postmenopausal status (AI Z 90.5%, TF Z 58%, p < 0.0001) and stage pT1b (AI Z 72.6%, TF Z 52%, p Z 0.02). No patients had loco-regional recurrence. Five- year PFS was 97.4% and OS was 99.2%. Non-HT patients had worse 5-year PFS (92.5% vs 98.4%, p Z 0.02) compared to patients with HT. On univariate analysis PFS was improved in HT patients (HR Z 5.09; 95%CI: 1.15-22.48, p Z 0.03). There was no difference in PFS seen between the HT patients when AIs were compared with TF, although the number of events in these two groups was small. Conclusions: In this relatively large cohort node negative, ER+ patients with tumors 1cm or less there was excellent local control and OS. Five year PFS was worse in patients without HT as shown in previous studies. Furthermore, there was no difference in outcome between AIs when compared with TF. This analysis supports the efficacy of AIs when compared with TF. Further studies are needed to determine if AIs are superior to TF in node negative, postmenopausal women with ER+ tumors that are 1cm or less. Author Disclosure: J.E. Panoff: None. T. Koru-Sengul: None. F. Miao: None. V. Gunaseelan: None. J. Wright: None. C. Takita: None.

2080 Once Daily Radiation Therapy for Inflammatory Breast Cancer L.B. Weinshank, M.J. Blanchard, J.W. Rooney, M.C. Stauder, I.A. Petersen, E.S. Yan, and N.N. Laack; Mayo Clinic, Rochester, MN Purpose/Objective(s): Inflammatory breast cancer (IBC) is an aggressive breast cancer variant that portends a poor prognosis, with 5-year overall survival (OS) typically reported at 40-45%. Many published series employ twice-daily radiation therapy (RT) to compensate for the rapid proliferation that has been demonstrated in IBC. Once daily radiation with daily bolus through treatment has been the standard RT technique used in trimodality therapy. Herein, we report our outcomes with this approach. Materials/Methods: Review of medical records was performed to identify patients treated with RT for IBC from 2000 through 2010. Patients with non-metastatic, clinically diagnosed IBC were included. OS and diseasefree survival (DFS) were assessed using the Kaplan Meier method. Recurrence in the chest wall or regional lymph nodes was defined as locoregional recurrence (LRR). IRB approved this protocol. Results: Fifty-two women were included in the analysis. Median age at diagnosis was 54 years (range, 23-83 years). The majority of patients had clinically involved nodes (81%) and tumors that were of ductal histology (90%), Nottingham grade III (65%) and estrogen receptor (ER) positive (56%). Ninety-four percent received neoadjuvant chemotherapy and 46% received adjuvant chemotherapy. All but 1 patient (98%) received chemotherapy at some point in their treatment. All patients underwent mastectomy and 98% had axillary dissection; one patient has sentinel lymph node biopsy. Ten patients had pathologic complete response to neoadjuvant chemotherapy. All patients were treated with adjuvant RT. Radiation was delivered in once daily fractions of 1.8-2.25 Gy (median 2 Gy). The chest wall and draining nodal volumes were treated to a median of 50 Gy (range, 46-60 Gy). Sixtytwo percent of patients received a boost to the mastectomy scar with a median dose of 10 Gy (range, 10-16 Gy). Daily bolus was employed in 90% of patients. This was, most commonly (68%), 1 cm in thickness. Median follow-up for the population was 3.6 years (range, 0.711.9 years). Five-year OS was 64%. Five-year DFS was 54%. Six women experienced LRR, for a crude local control rate of 88%. LRR was associated with poorer DFS and OS (p < 0.01 and p Z 0.02, respectively). On univariate analysis, age greater than 50 years correlated with better 5-year DFS (65% versus 40%, p Z 0.037) but had no effect on OS. ER status and response to chemotherapy were not associated with OS or DFS. Conclusions: Our outcomes with once daily RT for IBC compare favorably to other reports in the literature. This supports the efficacy of once daily treatments, which are more convenient for patients and less resource

Poster Viewing Abstracts S249 intensive. Women younger than 50 years of age had poorer DFS than their older counterparts, in keeping with previously reported data. Author Disclosure: L.B. Weinshank: None. M.J. Blanchard: None. J.W. Rooney: None. M.C. Stauder: None. I.A. Petersen: None. E.S. Yan: None. N.N. Laack: None.

2081 4Pi Therapy for Partial Breast Irradiation P. Dong,1 S. McCloskey,1 Y. Yang,1 T. Long,2 D. Ruan,1 E. Romeijn,2 D. Low,1 P. Kupelian,1 and K. Sheng1; 1UCLA, Los Angeles, CA, 2 University of Michigan, Ann Arbor, MI Purpose/Objective(s): External beam accelerated partial breast irradiation (APBI) is the least operator and equipment dependent APBI technique. However, elevated normal tissue doses have limited wide applicability of external beam APBI due to its poor conformality, potentially high normal tissue toxicities, and unacceptable cosmetic outcomes. Specifically, subcutaneous fibrosis and unacceptable cosmesis have been correlated with V50% of the whole breast reference volume. To improve the conformality of external beam APBI, we develop a novel 4pi algorithm that optimizes both non-coplanar beam orientations and fluences based on pre-computed deliverable beam geometry solution space. Materials/Methods: The 4pi algorithm was developed as follows. A beam geometry solution space was generated based on surface measurements of a LINAC gantry, couch, and the patient. Deliverable beams were identified by exhaustively searching all combinations of couch and gantry positions. A two-stage inverse optimization was performed to select the beams and optimize fluences in the beam geometry solution space. Specifically, the beam orientations were selected from 1162 non-coplanar candidate beams using a generalized matching pursuit algorithm, which was also used to select apertures from a candidate pool in the fluence optimization stage. Dose deposition coefficients were pre-calculated by superposition/ convolution and 6 MV x-ray poly-energetic kernels. External beam APBI plans were generated for 10 left sided breast cancer patients using the proposed 4pi algorithm, and compared to 4 field non-coplanar 3D conformal plans generated according to NSABP B39/RTOG 0413 protocol. Doses to organs-at-risk and the ipsilateral normal breast volume receiving greater than 50% prescription dose (V50%) were compared. Results: On average, breast V50% was reduced from 41% (range, 24%51%) to 31% (range, 18%-39%) using the 4pi planning method. Based on the dosimetric constraint of V50% <40%, all potential patients qualified for external beam APBI using the 4pi technique, whereas only 6/10 patients met this constraint using the 4 field non-coplanar 3D conformal approach. The ipsilateral lung volume receiving 30 Gy or higher and the highest 5% heart doses were reduced by 53% and 82%, respectively. All improvements were statistically significant (p < 0.001). Doses to the contralateral breast and lung were negligible (<1 Gy) for all patients with both planning techniques. Conclusions: The 4pi non-coplanar plans significantly improve dose conformity and OAR sparing compared with conventional 3D conformal plans yet remain practical to deliver benefiting from the pre-planning modeling of the patient specific beam geometry solution space. This technique represents a compelling non-invasive alternative to brachytherapy techniques. Author Disclosure: P. Dong: None. S. McCloskey: None. Y. Yang: None. T. Long: None. D. Ruan: None. E. Romeijn: None. D. Low: None. P. Kupelian: None. K. Sheng: None.

2082 Partial Breast Reirradiation for Patients With Ipsilateral Breast Tumor Recurrence A.E. Khouri, R. Leeming, R. Shenk, P. Silverman, C. Graham, and J. Lyons; University Hospitals of Cleveland, Case Medical Center, Cleveland, OH Purpose/Objective(s): Standard of care for in breast recurrence following whole breast irradiation is mastectomy. Following IRB approval, we have