Extracapsular Extension (ECE) of Lymph Nodes Predicts Locoregional Recurrence (LRR) in Breast Cancer - Is There a Role for Radiation?

Proceedings of the 51st Annual ASTRO Meeting displacement (SD) between 2 consecutive US during the course of radiotherapy were 5.8(6.0), 5.4(5.0) and 6.9(7.0) mm. The amount of TB displacements between weekly and daily US scans were not significantly different (p=0.1). The mean differences in the localization of the TB between US scans acquired from the same fraction were 0.9 (0.6), 0.9(0.7) and 1.1 (0.9) mm. Conclusions: Results from this study suggest that a 10mm PTV margin may be insufficient to account for TB displacement during radiotherapy. In the absence of image guidance, a PTV margin larger than 10mm is needed to cover the CTV 95% of the time in PBI or electron boost. This US based image-guided verification offers a potential solution for localizing the tumor bed, allowing patient alignment during daily radiotherapy. Breast radiotherapy techniques could benefit from daily IGRT to reduce the PTV. Author Disclosure: P. Wong, None; T. Muanza, None; E. Reynard, None; J. Barker, Resonant Medical, A. Employment; K. Robert, None; K. Sultanem, Resonant medical, F. Consultant/Advisory Board.

2036

Extracapsular Extension (ECE) of Lymph Nodes Predicts Locoregional Recurrence (LRR) in Breast Cancer - Is There a Role for Radiation?

K. Shah1, K. Albuquerque2, Y. Li2, C. Ershain2, K. Rychlik2 1

Loyola University Stritch School of Medicine, Maywood, IL, 2Loyola University Health System, Maywood, IL

Purpose/Objective(s): Our study focuses on understanding the significance of extracapsular extension (ECE) as a predictor of locoregional recurrence (LRR) in breast cancer patients. Materials/Methods: We retrospectively analyzed outcome data of 184 patients diagnosed with invasive breast cancer (stage I-III) at Loyola University Health System between 1998 and 1999. Data collection included descriptive (race, age, type of surgery), prognostic (tumor type/size, positive lymph nodes, metastasis), and pathologic parameters (grade, ER/PR/Her2Neu, ECE) as well as adjuvant therapy (chemo/hormone/radiation). We measured ECE in mm and then, grouped them accordingly: none, 0-2mm, and greater than 2mm. We recorded the date of first recurrence, type of recurrence (none, locoregional, and distant) and death from disease. The LRR was defined as any first recurrence with local/regional component (including patients who presented with distant and also had locoregional spread). Statistical analysis included chi-square and Fischer’s exact test to measure significance of ECE in regards to recurrence, and multinomial logistic regression was used to measure significance of predictive parameters. Kaplan-Meier survival analysis included estimated survival time and ECE differences. Results: Median age at surgery was 58.8 years. Surgery distribution: 86 (46.7%) breast conserving vs. 98 (53.3%) mastectomy. 123 (66.8%) patients received systemic therapy (chemo, hormone, or both). 105 (53.1%) patients had radiation therapy: 75 (71.4%) local, 30 (28.6%) locoregional. Of the 184 patients, 69 had recurrence (37.5%), with 27 locoregional component (14.7%) and 42 distant (22.8%). With univariate analysis, ECE was significantly associated with any recurrence (p=0.003), while ECE was also significantly associated with reduced disease-specific survival (p\0.001). On multinomial analysis, ECE was an independent predictor for LRR (p=0.043) (corrected for systemic therapy). Adding radiation to the regression model did not impact LRR (p = 0.581), but ECE still remained statically significant (p=0.040). The estimated survival time for patients with ECE greater than 2mm was 76.8 months, ECE less than 2mm was 80.2 months, and ECE negative was 105.3 months (Log Rank p = 0.014). Conclusions: ECE is a strong predictor for LRR even when correcting for adjuvant chemo, hormone, or radiation therapy in our series. ECE also has significant prognostic value for disease-specific survival. Almost half of the patients in our study did not receive adjuvant radiation and they were predominately in the mastectomy group, for whom radiation has shown to improve locoregional control. Larger studies are recommended to evaluate the role of radiation in preventing LRR in ECE positive patients. Author Disclosure: K. Shah, None; K. Albuquerque, None; Y. Li, None; C. Ershain, None; K. Rychlik, None.

2037

Consistent Skin and Rib Dose Reduction Using the Contura Multi-Lumen Balloon (MLB) Breast Brachytherapy Catheter: Preliminary Dosimetric Findings of a Phase II Trial

D. W. Arthur1, F. A. Vicini2, D. A. Todor1, T. B. Julian3, M. R. Lyden4 Virginia Commonwealth University, Richmond, VA, 2William Beaumont Hospital, Royal Oak, MI, 3Allegheny General Hospital, Pittsburgh, PA, 4BioStat International, Inc., Tampa, FL

1

Purpose/Objective(s): Initial dosimetric findings in patients treated with the Contura Multi-Lumen Balloon (MLB) breast brachytherapy catheter to deliver accelerated partial breast irradiation (APBI) on a multi-institutional phase I/II registry trial are presented. Materials/Methods: Patients were enrolled prior to catheter placement. CT-based 3D planning with dose optimization based on specific dosimetric goals was completed. APBI treatment of 34 Gy in 3.4 Gy fractions was delivered. Dosimetric planning goals were set to reflect reported best anticipated outcome and lowest toxicity as experienced with a single lumen balloon. Specifically, skin thickness required to be $5mm (i.e. \145% of prescribed dose (PD)) and decreased toxicity when skin thickness and rib distance $7mm (i.e. \125% of PD). For this trial, dosimetric goals included $95% of PD covering $90% of the target volume while assuring that max skin dose \125% of PD, max rib dose \ 145% of PD and V150 \ 50cc and V200 \ 10cc. The ability to achieve these dosimetric goals using the Contura MLB in relationship to the balloons proximity to skin and rib was analyzed. Results: To date, 100 cases have complete data sets available for review. Median age is 65.6 years and 25% had stage Tis, 66% with T1N0 and 9% with T2N0 (\3cm). Median tumor size was 1.2 cm. Utilizing the multi-lumen capabilities, all dosimetric criteria were met in 77% of cases. Evaluating dosimetric criteria individually, 89% and 90% of cases met skin and rib dose criteria, respectively. In 96% of cases, target volume coverage goals were met and in 99%, dose homogeneity criteria of V150 and V200 were satisfied. In all cases when skin and rib distances were judged to be close, dosimetric improvements were documented. When skin thickness was $5mm - \7mm (#19), median skin dose was limited to 121% (74 - 131.5) of PD and when \5mm (#12), median skin dose was 124.8% (100-134). When rib distance was \5mm (#31), median rib dose was reduced to 135% (104-178) of PD. In those cases (#10) when both skin thickness was \7mm and distance to rib was \5mm, median skin and rib dose were jointly limited to 120.6% and 140.1% of PD, respectively. Conclusions: Dose delivered by single lumen balloon based brachytherapy is directly related to skin thickness and distance to rib. A multi-lumen design removes the reliance of dose on device placement geometry. Contura MLB catheter use produced potential

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