Proceedings of the 52nd Annual ASTRO Meeting S241

Results: Statistical analysis of all patients (N = 116) revealed no significant differences in skin reactions when stratifying by type oflotion (RP vs. standard lotions), treatment delivery technique; intensity modified radiation therapy (IMRT) vs. standard tangentialfields (STF), and chemotherapy received. When stratifying by bra cup size (BCS), only week 7 showed a significant difference ingrade 3 skin reactions with D+ having 16% vs. 0% for both A/B and C (p = 0.010). Analysis of the subset of patients utilizing the RP(N = 61) revealed patients treated with IMRT vs. STF had significantly less grade 2 skin reactions at week 5 and week 6, 11% vs.56% (p = 0.001) and 23% vs. 69% (p = 0.004), respectively. However, at week 7 and 2 weeks post treatment there was no signif-icant difference in skin reactions between the two treatment technique groups. Stratifying by BCS showed at week 7, D+ BCS hada significantly larger number of grade 3 skin reactions 25% vs. 0% for BCS A/B and C (p = 0.024). However, by 2 weeks posttreatment the skin reactions showed no significant difference between treatment technique groups. The use of chemotherapydid not show any significant difference in skin reactions in the using RP. Analysis of the subset of patients utilizing the SC resultedin no significant difference when stratifying by treatment delivery technique, BCS, and use of chemotherapy. Subset analysis of thepatients treated with IMRT revealed significant difference in grade 2 skin reaction at week 6 between RP patients and SC, 22% vs.45% (p = 0.045), respectively. At the week 7 and 2 weeks post treatment time points there were no significant skin reactions notedbetween the two treatment technique groups.

Conclusions: Overall analysis revealed no difference in skin reaction between RP and SC at week 7 and 2 weeks post treatment.Larger breast size as evidenced by BCS D+ tended to have more grade three reactions. Also patients that received IMRT with RPhad less grade 2 skin reactions at week 5 and 6.

Author Disclosure: A.S. Maynard, None; C. Mitchell, None; A. Calcaterra, None.

2081 Interstitial High Dose Rate Brachytherapy for Early Stage Breast Cancer: Median 6 Year Follow-up of 268

Cases Using Multi-catheter Technique

P. J. Anderson1, R. J. Mark1,2, R. S. Akins1, M. Nair1

1Joe Arrington Cancer Center, Lubbock, TX, 2Texas Tech University, Lubbock, TX

Purpose/Objective(s): External Beam Radiation Therapy (EBRT) has been the standard of care for breast conservation radiationtherapy. Recent data indicates that Interstitial Implant and High Dose Rate (HDR) radiation afterloading compares very favorablyto EBRT in selected patients.

Materials/Methods: Patients with Tis, T1, and T2 tumors measuring # 4 cm, negative surgical margins, and # 3 axillary lymphnodes were judged to be candidates for Interstitial Implant. Implants were performed under Stereotactic Mammographic guidancewith conscious sedation and local anesthesia. The implants were placed with a custom designed template using from 3 to 8 planes,and 8 to 74 needles. Catheters were subsequently threaded thru the needles, and the needles removed. Catheter spacing was 1.0 to1.5 cm. Radiation Treatment planning was performed using CT Scanning and the Plato System. Treatment volumes ranged from 25cm3 to 359 cm3. HDR treatment was given using the Nucletron afterloading system. The breast implant volume received 3400 c Gyin 10 fractions prescribed to the Planning Target Volume, given BID over 5 days.

Results: Between 2000 and 2010, 268 patients underwent Interstitial HDR Implant. The procedure was well tolerated. No patientrequired hospital admission. With a median follow-up 72 months (range, 6-128 months), local recurrence occurred in 3.7% (10/268). Cosmetic results were good to excellent in 89.5% (240/268) of the patients. There were no infections. Wound healing com-plications developed in 3.0% (8/268). Three of these patients had received anthracycline based Chemotherapy. The other five hadlarge (. 200 cm3) implant volumes, catheter spacing of 1.5 cm, and V-150% of . 30%. Two patients healed after 6 months ofconservative treatment. Surgery was required in six patients who developed fat necrosis.

Conclusions: With median 72 month follow-up, Breast Conservation radiation therapy utilizing Interstitial Multi-Catheter HDR Im-plant has yielded local recurrence rates and cosmetic results which compare favorably to EBRT in selected patients. Treatment withanthracycline based Chemotherapy, large (. 200 cm3) implant volumes, and V-150% . 30%, appear to be relative contraindicationsto Interstitial HDR Implant. Finally, catheter spacing of 1 cm yielded optimal dosimetry and minimized complications. Compared toMammosite and Contura techniques, the Interstitial Multi-Catheter method offers greater flexibility of radiation delivery. Advantages,include no concern regarding surgical cavity shape irregularities, balloon conformality to surgical cavity, balloon rupture, balloon move-ment, air gaps, hematoma, seroma, skin balloon proximity to skin, balloon shape distortion, and catheter movement within the balloon.

Author Disclosure: P.J. Anderson, None; R.J. Mark, None; R.S. Akins, None; M. Nair, None.

2082 Is the 1 cm CTV Margin Used in Breast Balloon Brachytherapy Equivalent to a 1.5 cm CTV Margin in

External Beam Partial Breast Irradiation? A Deformable Registration Study

L. Kim, S. Shaitelman, I. Grills, F. Vicini, A. Martinez, D. Yan

William Beaumont Hospital, Royal Oak, MI

Purpose/Objective(s): Different expansion margins are typically used to define the clinical target volume (CTV) in acceleratedpartial breast irradiation (APBI) delivered via balloon brachytherapy (1 cm) vs. three-dimensional conformal radiotherapy (3D-CRT) (1.5 cm). Previous studies have argued using geometric reasoning that these margins should be equivalent. In this study,deformable registration is used to generate directly comparable treatment volumes on CT sets with and without a brachytherapyballoon.

Materials/Methods: Ten patients previously treated with MammoSite were studied. Each patient had two CT scans, one with andone without the balloon. In-house deformable registration software was used to deform the brachytherapy target volume onto theballoonless CT set. Results of the deformation were verified using anatomical landmarks common to both image sets. The de-formed brachytherapy target volume was compared to volumes based on uniform lumpectomy cavity expansions of 1 and 1.5cm. Non-uniform cavity expansions in 6 directions (left, right, anterior, posterior, superior, inferior, 60 expansions total) werealso chosen to match the deformed brachytherapy target’s dimensions and volume.

Results: Of the sixty direction-specific cavity expansions used to match the deformed brachytherapy target, only 22 exceeded 1 cm,and none exceeded 1.5 cm. Only small portions of the deformed targets could be found to lie 1.5-2 cm from the cavity. Fourteen of60 expansions were smaller than 1 cm. These decreases in effective treatment margin were attributed to poor cavity-to-balloon

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conformance. In terms of volume, the deformed brachytherapy targets were on average 8 ± 9% larger and 37 ± 4% smaller than 3D-CRT targets based on uniform expansions of 1 and 1.5 cm respectively.

Conclusions: Deformable registration suggests that although balloon brachytherapy typically does treat an effective margin greaterthan 1 cm, its treatment volumes are significantly smaller, from both a margin and volume standpoint, than CTVs based on a 1.5 cmmargin, which are often used in interstitial brachytherapy and 3D-CRT. If long-term patient follow-up shows a difference in tumorrecurrence rates between APBI modalities, this could be an explanation. Alternatively, if there is no difference in recurrence, thenthis result may support margin reduction for 3D-CRT to reduce toxicity risks.

Author Disclosure: L. Kim, None; S. Shaitelman, None; I. Grills, None; F. Vicini, None; A. Martinez, None; D. Yan, None.

2083 Omitting Postoperative Radiation after Excision for Ductal Carcinoma In Situ of the Breast

J. Lee1, D. H. Choi1, S. J. Huh1, W. Park1, H. Nam1, J. H. Yang2, S. J. Nam1, J. E. Lee1

1Dept. of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic ofKorea, 2Dept. of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea

Purpose/Objective(s): There is a hypothesis that a subset of patients with ductal carcinoma in situ (DCIS) of the breast will notbenefit from radiation therapy (RT) after local excision. Based on this hypothesis, we conducted a prospective study evaluating theresult of omitting RT in patients with low-risk DCIS.

Materials/Methods: From 1999 to 2005, 54 patients who were diagnosed with DCIS underwent breast-conserving surgery with-out RT. The indication of omitting RT was tumor equal or smaller than 1 cm, non-comedo type and resection margin more than 3mm. Tamoxifen was added in 41 patients.

Results: During follow-up period of median 60 months, 3 (5.6%) patients experienced local recurrence; one with DCIS and twowith invasive ductal carcinoma. No regional/distant failure or disease-specific death was occurred.

Conclusions: With relatively short-term follow-up, excision without postoperative RT achieved high local control rate in selectedDCIS patients. Randomized trial with longer follow-up is needed to evaluate the safety of omitting RT and to identify patient se-lection criteria.

Author Disclosure: J. Lee, None; D.H. Choi, None; S.J. Huh, None; W. Park, None; H. Nam, None; J.H. Yang, None; S.J. Nam,None; J.E. Lee, None.

2084 Comparative Analysis of Dose-volume Histogram between Multistatic Field Technique and Three

Dimensional Radiation Therapy Planning for Postoperative Radiation Therapy of Left Breast Cancer

S. Moon

Soonchunhyang University Hospital, Radiation Oncology, Bucheon-Si Gyeonggi-Do, Republic of Korea

Purpose/Objective(s): The purpose of this study was to determine the clinical feasibility of tangential multistatic field techniqueand to compare dosimetric factors with 3-dimensional conformal radiation therapy (3DCRT).

Materials/Methods: Twenty nine left breast cancer patients were randomly selected for comparison of MSF radiation treat-ment plan with 3DCRT. Both MSF planning and 3CDRT planning were performed employing the Plato Planning System (Nu-cletron, Netherlands). The dosimetric factors compared were V95 (the percentage of target volume receiving $95% ofprescribed dose), V105, V110, and dose homogeneity index, DHI (percentage of target volume receiving between 95% and110% of prescribed dose).

Results: The mean V95, DHI, V105, and V110 for target volume for MSF vs. 3D were : 90.5 (SD:4.6) vs. 90.01 (SD: 3.1), 90.1(SD:4.0) vs.86.23 (SD:7.1), 22.1 (SD:15.8) vs. 51.21 (13.1), 2.2 (SD:5.8) vs. 9.35 (SD:8.4), respectively. DHI was increasedby 4.49% with MSF compared to 3DCRT (p \ 0.05). The reductions of V105 and V110 for the MSF compared to 3DCRT were56.8% and 76.4%, respectively (p = 0.001 and p = 0.002). The V10, V20, and V30 for heart with MSF were 15.7 (SD:5.4), 10.3(SD:7.5), and 11.1 (SD:6.2), respectively. The percent reduction in dose with MSF compared to 3DCRT were 10.2%, 11.9%,and 13.2%, respectively. Similarly the V10, V20, and V30 for the ipsilateral lung and the percentage of volume of contralateral vol-ume lung receiving . 5% of PD were reduced by 6.74%, 1.65%, 10.1%, and 37.5%, respectively. The mean of total MU used forthe MSF and 3DCRT was not about the same (235 vs. 389). The reduction in total MU with MSF was statistically significant (p =0.03).

Conclusions: The dosimetric data showed that improved dose homogeneity in the breast and reduction in the dose to lung and heartfor MSF treatments, which may be of clinical value in potentially contributing to improved cosmetic results and reduced late treat-ment-related toxicity.

Author Disclosure: S. Moon, None.

2085 Daily MV Portal Imaging with 2D Matching of Supraclavicular Fields Improves Conformal Radiotherapy

Setup Accuracy for Multiple Field Breast Treatments

K. O’Leary1, P. Clancy1, L. Sroczinski2, L. Kachnic1, M. Qureshi1, A. Hirsch1

1Boston Medical Center, Boston, MA, 2Jordan Hospital, Plymouth, MA

Purpose/Objective(s): Multiple field breast treatments require precise positioning of the supraclavicular field which is tradition-ally assessed via daily surface anatomy and weekly MV portal images. We investigated the placement of the supraclavicular field inrelation to the setup tattoo using MV imaging with 2D image matching overlay of the digitally reconstructed radiograph (DRR) in