Positive Axillary Lymph Node Number Rather Than Total Lymph Node Number Removed Associates With Arm Lymphedema Among Postoperative Breast Cancer Patients Over Radiation Therapy Course

Volume 96  Number 2S  Supplement 2016

Poster Viewing

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3DCRT: 930.3 mL vs. 729.8 mL (P Z 0.003) for V5 and 762.5 mL versus 649.8 mL (P Z 0.023) for V10. The same relationships held for the upper and lower M-groups. Conclusion: IMRT significantly reduces the volume of neck/shoulder/trunk musculature receiving intermediate and high doses of radiation compared with 3DCRT in women receiving RNI in a routine clinical practice. Prospective evaluation is needed to determine if IMRT can reduce long term morbidity associated with radiation dose to the musculature and to help define the optimal dose volume constraints for this structure. Author Disclosure: J.G. Bazan: None. D.J. DiCostanzo: None. A.M. Quick: None. R.L. Young: None. J.L. Wobb: None. J.R. White: N/A; NRG Oncology, NCI Breast Cancer Steering Committee.

Conclusion: WBRT seems to decrease the incidence of leptomeningeal seeding after resection for brain metastases in breast cancer patients. Especially for patients with tumor in adjacent to CSF flow, WBRT rather than localized RT needs to be considered as postoperative treatment. Author Disclosure: B. Ha: None. S. Chung: None. Y. Kim: None. H. Gwak: None. I. Park: None. S. Lee: None. T. Kim: None. D. Kim: None. S. Kang: None. J. Chang: None. C. Suh: None.

2137 Radiation Dose to the Musculature of the Neck/Shoulder and Trunk in Women With Breast Cancer Undergoing Regional Nodal Irradiation: A Comparison of Intensity Modulated Radiation Therapy Versus 3D Conformal Radiation Therapy J.G. Bazan,1 D.J. DiCostanzo,2 A.M. Quick,3 R.L. Young,1 J.L. Wobb,1 and J.R. White1; 1The James Cancer Hospital and Solove Research Institute, Wexner Medical Center at The Ohio State University, Department of Radiation Oncology, Columbus, OH, 2Ohio State University, Columbus, OH, 3The Ohio State University, Department of Radiation Oncology, Columbus, OH

2138 Positive Axillary Lymph Node Number Rather Than Total Lymph Node Number Removed Associates With Arm Lymphedema Among Postoperative Breast Cancer Patients Over Radiation Therapy Course Z. Li, W. Geng, J. Zhang, J. Yin, D. Kong, J. Kong, J. Zhang, and A. Zhang; The Fourth Hospital of Hebei Medical University, Shijiazhuang, China

Purpose/Objective(s): Higher rates of ipsilateral shoulder, arm, and chestwall morbidity are seen with the addition of regional nodal irradiation (RNI) to whole breast (B) or chest wall (CW) only radiation (RT). Excess RT dose to the muscles of the neck/shoulder and trunk regions may contribute to this long term morbidity. We hypothesized that intensitymodulated radiation therapy (IMRT) decreases the volume of muscle receiving high doses of radiation compared to 3D conformal radiation therapy (3DCRT) in women treated with RNI. Materials/Methods: We identified cases that received RNI in our department from the date IMRT was first used April 2013 to April 2015. Target volumes routinely contoured for treatment planning on all included the B/ CW planning target volume (PTV), supraclavicular (SCV PTV), internal mammary node PTV, and axilla PTV. For all cases, normal tissues are standardly contoured and must meet dose constraints including the heart, bilateral lungs, contralateral breast, and thyroid. No planning constraints are set for muscle groups. We retrospectively contoured the musculature of the neck/shoulder and trunk from 2 cm above the SCV PTV to 2 cm inferior to the B/CW PTV and defined this as Musculature (M). The M structure was divided into 2 M-groups: Upper (beginning 2 cm cranial to the SCV PTV and ending 1 slice superior to the cranial aspect of the B/CW PTV) and lower (beginning at the cranial edge of the B/CW PTV and ending 2 cm below the B/CW PTV). The dose volume histogram (DVH) was analyzed to determine the volume of M and each M-subgroup (in mL) receiving at least 50 Gy (V50), 45 Gy (V45), 40 Gy (V40), 30 Gy (V30), 20 Gy (V20), 10 Gy (V10) and 5 Gy (V5). We used the t-test to examine for significant differences (P < 0.05) in mean volume at each dose level between IMRT and 3DCRT. Results: We identified 132 consecutive cases that received RNI (21 B, 111 CW). IMRT significantly reduced the amount of M receiving RT compared to 3DCRT: 17.4 mL versus 132.5 mL (P Z 0.022), 49.9 mL versus 360.7 mL, 88.0 mL versus 441.7 mL (P<0.0001), 239.8 mL versus 507.8 mL (P<0.0001), and 467.2 mL versus 584.4 mL (P Z 0.015) for V50, V45, V40, V30, and V20 respectively. IMRT significantly reduced V20-V50 in the upper M-group and V30-V50 in the lower M-group. Low dose radiation to the M was significantly higher in patients receiving IMRT versus

Purpose/Objective(s): To evaluate how radiotherapy (RT) and clinical factors associate with breast cancer related lymphedema (BCRL) events over the first postoperative RT course Materials/Methods: Two hundred eighty-one one-sided BC women admitted consecutively for RT from November 2013 to February 2015 after breast conserving surgery (BCS) or mastectomy (MAS) with ALND and 6 - 8 cycles of chemotherapy were prospectively analyzed. Standard 50-51 Gy/25f/5-6w dose was delivered to ipsilateral breast (+ electron boost 10 Gy on BCS cavity)/chest wall and regional LN areas. Bilateral upper limb volumes (ULV) measured by water displacement were utilized to assess BCRL through calculating their difference (illness minus healthy side) before and immediately after RT. Both repeated ULV differences (ULVd) and BCRL events (defined as  200 mL) over RT period were analyzed by using Mixed and GEE models to evaluate the effects of RT and groups of LN number removed in total and positive. Coefficients and/ or their corresponding relative risk (RR) and its 95% CI from models were calculated with/out covariates which included age, BMI, tumor side and size, and surgery type. Results: Mean age 46.2 (8.7 SD) yrs and BMI 26.8(3.5) kg/m2, left tumor 52%, path tumor size 2.1 (1.2) cm, MAS was 97%. First RT after surgery had median 167 days. Overall, ULVd had mean (SD, median) 40.6 (123.9, 30.0) before RT and 42.9 (117.2, 30.0) mL after RT. By groups of LN total # removed of <10 (n Z 32), <15 (n Z 65), <20 (n Z 99) and  20 (n Z 85), these statistics were 31.3 (112.5,45.0), 51.0 (130.8,30.0), 33.3 (112.9, 25.0), 44.5 (135.2, 27.0) before RT and 36.0 (91.3,40.0), 56.2 (122.8, 47.5), 35.4 (121.3, 20.0), 44.2 (117.8, 30.0) after RT. By groups of LN+ # removed of 0 (n Z 58), <4 (n Z 119), <10 (n Z 74), and 10 (n Z 30), these statistics were 5.8 (101.1, 12.5), 43.6 (134.7, 25.0), 60.7 (131.0, 40.0), 47.1 (85.3, 66.0) before RT and 22.6 (95.7,20.0), 40.7 (121.6, 30.0), 62.4 (131.1, 22.5), 42.3 (97.0, 50.0) after RT. Univariate and adjusted Mixed models on ULVd indicated the significant effect of LN+ # group only (no data). Table 1 shows the GEE model results on repeated BCRL

Abstract 2138; Table 1. BCRL Incidence (%)

RT LN+ 0 1-3 4-9 10

Univariate

Before RT

After RT

RR

95% CI

7.5(21/279)

8.6(24/280)

1.156

(0.741

3.4( 2/58) 9.2(11/119) 11.0( 8/73) 0.0( 0/29)

1.8( 1/57) 10.9(13/119) 12.2( 9/74) 3.3( 1/30)

1.000 4.271 4.959 0.675

ref. (1.236 (1.343 (0.070

Multivariable P

RR

-1.804)

0.523

1.165

(0.727

-1.866)

-14.761) -18.311) - 6.486)

ref. 0.022 0.016 0.734

1.000 4.147 3.758 0.599

ref. (1.196 (0.946 (0.060

-14.374) -14.933) - 5.954)

* 2 patients were maximally excluded from analyses due to their absent records of ULV measurements.

95% CI

P 0.526 ref. 0.025 0.060 0.662

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International Journal of Radiation Oncology  Biology  Physics

events by LN+ group. No significant P values were found at all GEE model results by LN total number group (no data). Conclusion: Positive axillary LN number removed associates with arm lymphedema among BC patients. RT does not increase BCRL over the first postoperative RT course. Long term effect of RT on BCRL needs follow-up data for evaluation. Author Disclosure: Z. Li: None. W. Geng: None. J. Zhang: None. J. Yin: None. D. Kong: None. J. Kong: None. J. Zhang: None. A. Zhang: None.

UZ Brussel, Vrije Universiteit Brussel, Brussels, Belgium, 2CHU de Martinique, Fort de France, Martinique

2139 Does Achieving Pathologic Complete Response From Neoadjuvant Chemotherapy (NAC) for Breast Cancer Lead to Higher Rates of Breast Conservation Therapy? R.L. Young, J.G. Bazan, J.L. Wobb, C. Decker, and J.R. White; The James Cancer Hospital and Solove Research Institute, Wexner Medical Center at The Ohio State University, Department of Radiation Oncology, Columbus, OH Purpose/Objective(s): Neoadjuvant chemotherapy (NAC) is more frequently used for treatment of operable breast cancer since it has the established benefits of identifying those with improved prognosis based on disease response and enabling more women to undergo lumpectomy and radiation for breast conservation therapy (BCT). With the use of new, targeted agents in combination with traditional chemotherapy, pathologic complete response (pCR) rates have dramatically increased in select groups. We hypothesized that we would see more breast conservation in those women that achieve pCR from undergoing NAC at our institution. Materials/Methods: The Institution Cancer Registry was used to identify women who had undergone NAC between 2009 and 2014, excluding women who would not qualify for BCS (T4d), cN3, or metastatic disease. Tumor characteristics (histology, grade, and receptor status), clinical (c) and pathological (yp) staging, and loco-regional management (BCT, mastectomy and RT use) were recorded. SAS was used for all statistical analyses. Results: A total of 396 women underwent NAC during the study period. Most (71%) were cStage II with 54.8% cN+, 44.7% cN0, 59.3% cT2 tumors, 55.8% Grade 1-2, and 44.2% Grade 3. Hormone receptor positive disease was noted in 54.8%, HER2 was positive in 31.1%, and 31.1% were triple negative (TN). Clinical stages I and III comprised 11.4% and 16% of the group, respectively. One third of women (33.8%) achieved a pCR (ypT0N0) with specific breast response as follows: 38% ypT0, 37% ypT1, 20% ypT2, 4% ypT3, and 1% ypT4. The rate of pCR was 42.7% for TN, 50.5% for HER2+, and 24% for hormone sensitive. Nodal response was 62% ypN0, 22% ypN1, 11% ypN2, and 5% ypN3. Mastectomy was done for 69.2% (274/396) rather than BCS (30.8%) following NAC. Of note, 15% of women (58/396) underwent b/l mastectomies (contralateral prophylactic). On Chi-square analysis, the use of BCS versus mastectomy did not correlate with achievement of pCR; BCT 38.5% versus 31.8% for mastectomy (P Z 0.1885). Specifically, BCT was performed for 36% ypT0/Tis, 36% ypT1, 21% ypT2, and 5.6% ypT3. Breast surgery type did correlate with overall downstaging (P Z 0.0002). Approximated molecular subtype was not related to usage of BCS (P Z 0.1214e0.6101). Conclusion: Despite demonstrating a pCR rate comparable to other current data, we did not find higher rates of BCT compared to mastectomy in women whose disease achieve pCR after NAC. These patterns of surgical management observed in our institution may reflect national trends in which mastectomy continues to be favored over BCT even among women with complete responses to NAC therapy. Author Disclosure: R.L. Young: None. J.G. Bazan: None. J.L. Wobb: None. C. Decker: None. J.R. White: member; National Cancer Institute Breast Cancer Steering Committee. Co-chair; NRG Oncology.

2140 Breast Respiratory Motion in Free Breathing Assessed by 4Dimensional Computed Tomography V. Vinh-Hung,1,2 T. Gevaert,1 K. Tournel,1 D. Verellen,1 N. Leduc,2 T. Reynders,1 T. Mulliez,1 and M. De Ridder1; 1Radiotherapy Department,

Purpose/Objective(s): In order to assess whether respiratory motion should be accounted for in the radiation treatment of the breast, we evaluate displacements of the breast during free breathing as measured by 4D-CT. Materials/Methods: The radiotherapy department’s records of women undergoing thoracic free breathing 4D-CT regardless of pathology were retrospectively reviewed. Mastectomy cases and repeated 4D-CT’s were excluded. Transversal and sagittal displacements of the right and left breast’s surface at different respiratory phases were measured at the nipple and on the 4 quadrants at 5.7 cm distance from the nipple. Comparisons used the 2-sided t-test. Identification of groups of patients used KMeans clustering. Results: Sixty-eight women were identified. The overall largest motion measured in any patient ranged from 1.3 to 10.4 mm, mean m Z 3.8 mm, standard deviation Z 1.7 mm. By breast location, the means of the max displacements were: upper inner quadrant right (UIQR) 2.8 mm vs. lower inner quadrant right (LIQR) 1.9 mm, P < 0.0001; upper outer right (UOQR) 3.0 mm vs. lower outer right (LOQR) 2.2 mm; upper inner left (UIQL) 2.7 mm vs. lower inner left (LIQL) 1.8 mm, P < 0.0001; upper outer left (UOQL) 2.7 mm vs. lower outer left (LOQL) 2.0 mm, P < 0.0001, nipple right 2.4 mm vs. left 2.2 mm, P Z 0.0895. KMeans identified 3 clusters: group 1 small motion, N Z 34 (50%) patients, m Z 2.7 mm, SD Z 0.9; group 2 intermediate motion, N Z 25 (36.8%), m Z 4.3 mm, SD Z 1.0; group 3 (including one outlier) large motion, N Z 9 (13.2%), m Z 6.6 mm, SD Z 1.7. Conclusion: Respiratory motion was significantly larger in the upper quadrants as compared with the lower quadrants. Stereotactic radiation techniques might be feasible in Group 1 without requiring respiratory management. The majority of patients in this study (86.8%) presented with small respiratory motion of 2.7-4.3 mm, indicating that conventional radiation treatment without breathing control appears adequate, with a caveat regarding the differences of movements according to location. Clustering indicates that 13.2% of patients might benefit from respiratory control for their radiation treatment. Author Disclosure: V. Vinh-Hung: Chairman; INRWG. Clinical research; IGRG. T. Gevaert: None. K. Tournel: None. D. Verellen: Treasurer; ESTRO. N. Leduc: None. T. Reynders: None. T. Mulliez: None. M. De Ridder: Chairman; UZ Brussel.

2141 Assessing Long-Term Complication Rates in Patients Undergoing Immediate Postmastectomy Breast Reconstruction and Adjuvant Radiation R. Sacotte,1 N. Fine,2 J.Y. Kim,2 M. Alghoul,2 K. Bethke,3 N. Hansen,3 S.A. Khan,3 S. Kulkarni,3 J.B. Strauss,4 J.P. Hayes,4 and E.D. Donnelly4; 1 Feinberg School of Medicine, Northwestern University, Chicago, IL, 2 Division of Plastic and Reconstructive Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL, 3Department of Surgery, Northwestern University Robert H. Lurie Comprehensive Cancer Center, Chicago, IL, 4Department of Radiation Oncology, The Robert H. Lurie Comprehensive Cancer Center, Chicago, IL Purpose/Objective(s): Postmastectomy radiation therapy (PMRT) for breast cancer increases survival, decreases local recurrences, and is a pillar of care in locally advanced disease. While immediate postmastectomy breast reconstruction has been shown to significantly improve psychosocial outcomes, it has also been linked to increased complications when followed by PMRT. Though there are multiple studies assessing and comparing the complication rates of immediate tissue expander/implant reconstructions (TE/I) and autologous tissue reconstructions (ATR) when PMRT is utilized, there are few with long term follow up. This study aims to quantify the long term complication rates of PMRT following immediate reconstruction and timing of complications in a large patient population.