112 Abstracts / Brachytherapy 7 (2008) 91e194

median 8 Gy was applied. In the case of a massively incomplete excisiona mastectomy was performed. This was the case in 29 cases and thesepatients were excluded from analysis. Also excluded were 8 patients whodid not receive external beam radiotherapy to the breast. The excisionwas microscopically complete for 129 LDR patients and 207 PDRpatients. Median followup was 10.4 years in the LDR group and 7.4 yearsin the PDR group.Results: There was no statistically significant difference in 7-year localrecurrence-free rate, being 91.7% (95% CI 87.1 to 96.2) and 95.0% (95%CI 92.1 to 97.9) in the LDR and PDR group, respectively (log rank P 5

0.18). The hazard ratio (HR) for local recurrence was 0.61 (95% CI 0.29to 1.27) with LDR as the reference group. When adjusting for potentialconfounders the HR increased to 1.06 (95% CI 0.48 to 2.34). Overallsurvival was not significantly different in both groups with a 7-yearoverall survival rate of 80.3% (95% CI 74.0 to 86.6) and 82.1% (95% CI77.2 to 87.0) for the LDR and PDR groups, respectively (log rank P 5

0.58).Conclusions: In this first report on a comparison between LDR and PDRboost as part of breast conserving treatment, the choice of the boostmodality is equally effective in preventing local recurrences in the longterm. Also no difference in overall survival was noticed. An office hourPDR schedule is not only more convenient to the patient for boosttreatment in breast conserving therapy, but can also safely replacecontinuous LDR brachytherapy.

OR57 Presentation Time: 8:10 AM

APBI outside the box: Outcome analyses in ‘‘high-risk’’ patients

eligible for the NSABP B-39/RTOG 0413 trial

Charles Hodge, M.D., Michael Christensen, B.S., Jarrod Adkison, M.D.,

Rakesh R. Patel, M.D. Human Oncology, University of Wisconsin,

Madison, WI.

Purpose: The NSABP B-39/RTOG 0413 is a multi-institutionalrandomized trial for patients with early stage breast cancer comparinglumpectomy followed by either accelerated partial breast irradiation(APBI) or six weeks of whole breast irradiation. In December 2006, thetrial closed enrollment to low-risk patients. Since then, patient accrual hasseen a significant decline, with the theory being that physicians are lesscomfortable treating ‘‘higher-risk’’ patients with APBI. In this study, weexamine outcomes in this high-risk patient subset treated with APBI atour institution.Methods and Materials: Between 2000 and 2005, 273 women with earlystage breast cancer were treated with lumpectomy followed by APBI,using either multi-catheter interstitial brachytherapy (n 5 247) orMammoSite� (n 5 26). All patients received 34 Gy in 10 twice-dailyfractions via high-dose rate iridium-192 brachytherapy. All womenincluded in this analysis met inclusion criteria for NSABP B-39/RTOG0413. For this analysis, the patients were separated into two groups: high-risk patients, who satisfied one or more of the ‘‘high-risk’’ criteria (!50years, ER negative, and/or positive nodes; n 5 90), and low-risk patientswho comprise the remainder of the cohort (n 5 183). The former grouprepresents the cohort that remains eligible for the Intergroup trial. Theoutcomes of the two cohorts were analyzed and compared.Results: The median followup of the entire cohort was 48.4 months (47.9months for low-risk and 49.7 months for high-risk patients). There was nosignificant difference for local control at five-years between the low andhigh-risk groups (97.8% versus 93.6%; p 5 0.29). There were 4ipsilateral breast recurrences in each group. There was no significantdifference in five-year overall survival between the low- and high-riskgroups (92.1% versus 89.5%, respectively; p 5 0.75).Conclusions: There is no statistically significant difference in five-yearoutcomes for patients that are deemed at higher risk on the currentNSABP B-39/RTOG 0413 Intergroup trial. The local control and overallsurvival rates observed in high-risk patients in this series are concordantwith those seen in contemporary APBI trials with adequate followup.This clinical data supports the inclusion of this high-risk population in theIntergroup study.

OR58 Presentation Time: 8:20 AM

Dosimetric correlation of clinical fat necrosis in patients treated

with multi-catheter breast brachytherapy

Rakesh R. Patel, M.D., Rupak Das, Ph.D. Human Oncology, University of

Wisconsin, Madison, WI.

Purpose: To evaluate the correlation of dosimetric variables withdevelopment of clinical fat necrosis in patients treated with image-guidedhigh-dose-rate (HDR) multi-catheter accelerated partial breast irradiation(APBI) with 3D CT-based treatment planning.Methods and Materials: 172 women with favorable breast cancer weretreated with lumpectomy + APBI from May 2002 through December2005. Only patients with a minimum of 12 months followup wereincluded in this analyses. All patients met the selection criteria for theNSABP B-39/RTOG 0413 trial. Post-lumpectomy APBI utilized animage-guided multi-catheter technique. The patients were treated to 34Gy in 10 twice-daily high-dose-rate fractions utilizing Iridium-192. ThePTV was defined as the seroma + 1.5-2 cm margin modified to 5 mmfrom skin and pectoralis muscle. 3D CT-based planning was performed tocover 100% of the seroma and 98% of the PTV. Several dosimetricvariables were analyzed including number of catheters, PTV, volumes oftissue encompassed by the 100%, 150%, 200%, 250%, and 300% isodoselines (V100, V150, V200, V250, V300), the correlating dosehomogeneity indices defined as V150, V200, V250, and V300 asa fraction of the V100 as well as the ratio of V100: PTV.Results: The median followup of all patients was 35.5 months (range: 13e57months). Clinical fat necrosis determined by RTOG late toxicity criteriaoccurred in 25 of 172 women (14.5%). The variables that significantlycorrelated with fat necrosis were PTV (p 5 .006), V150 (p 5 .004), V200(p 5 .001), V250 (p 5 .001), and V300 (p 5 .003). The number ofcatheters, the V100, DHI at any level and V100/PTV was not significant.Conclusions: This study validates analyses published by Wazer (IJROBP2001:50;107-111) that larger regions of ‘‘hot spots’’ (V150 and V200) arecorrelated with a higher incidence of fat necrosis. Additionally, we findthat the V250, V300, and PTV itself are all significantly correlated toclinical fat necrosis. The fact that no DHI was significantly correlatedwith fat necrosis suggests that the fraction of tissue in the ‘‘hot spots’’does not matter. Rather, it is the absolute volume of tissue within thesehigher isodose lines that puts the patient at risk. Image-guided techniquesand 3D CT-based planning has allowed more rigorous dosimetric analysisof multi-catheter APBI. Studies are ongoing to analyze regions of fatnecrosis within the PTV and their dose-volume correlates.

PHYSICS ORAL PRESENTATION SESSION 2

(HDR QA, radiobiology, image guided)

Tuesday May 6, 2008

11:00 AMe12:00 PM

OR59 Presentation Time: 11:00 AM

Seed imaging and reconstruction quality of different CT parameters

and various seed models

Frank-Andre Siebert, Ph.D.1 Marisol De Brabandere, M.Sc.2 Christian

Kirisits, Ph.D.3 Gyoergy Kovacs, M.D., Ph.D.4 Jack Venselaar, Ph.D.5

1Radiotherapy, University Hospital of Schleswig-Holstein, Campus Kiel,

Kiel, Germany; 2Radiotherapy, University Hospital Gasthuisberg, Leuven,

Belgium; 3Radiotherapy, Medical University Vienna, Vienna, Austria;4Interdisciplinary Brachytherapy, University Hospital of Schleswig-

Holstein, Campus Luebeck, Luebeck, Germany; 5Dr. B. Verbeeten

Instituut, Tilburg, Netherlands.

Purpose: The Braphyqs group is the physics task group of GEC-ESTRO.This group presents results of phantom investigations of seedreconstructions using computer tomography. Different seed models andCT parameters were studied for the seed imaging in the post-planningprocedure using a solid phantom.Methods and Materials: The Perspex phantom (Kiel-Phantom) wasequipped with a test configuration of 17 non-radioactive seeds. To