Breast Radiation Therapy (RT) Using Simultaneous Integrated Boost (SIB): Which Is the Optimal Intensity Modulated RT (IMRT) Technique?

Volume 90  Number 1S  Supplement 2014

Poster Viewing Abstracts S227

Purpose/Objective(s): DIBH during radiation of left breast cancers has been shown to reduce heart dose, potentially reducing late cardiac ischemic events. We sought to improve the accuracy of treatment delivery with DIBH by using electromagnetic surface transponders. Herein we examine improvement in intra-fraction motion during DIBH and dose reduction to the heart with this technique. Materials/Methods: Fifteen patients were included in this retrospective IRB-approved study. Patients were planned and treated using DIBH. We also obtained treatment-position free-breathing (FB) CT scans and fused them to DIBH scans based on breast position to compare mean heart (MH) and left anterior descending coronary artery (LAD) dose between techniques. We used daily port films to verify treatment position. Surface transponders were used to track the position of the chest wall (CW) during port film and treatment. We retrospectively used transponder tracking reports to compare CW position during treatment to that at the time of port film and to determine CW motion in each axis during beam-on time and each total breath hold period. Total breath hold period CW motion was measured from just after the patient held her breath to just before she released it. This represented a surrogate for potential CW position during an unmonitored breath-hold. A paired t-test was used to compare heart dose with and without DIBH and CW excursion during beam-on and total breath hold time. Results: DIBH significantly reduced MH and LAD dose versus FB plans (MH 1.26  0.51 Gy vs 2.84  1.55 Gy, p  0.001), (LAD 5.49  4.02 Gy vs 18.15  8.78 Gy, p  0.001). Mean CW positional difference from port film  2SD and CW excursion 1SD during breath hold and beam-on time are reported in the Table . In each dimension, CW excursion during breath hold was significantly greater than CW position during beam-on time with p  0.001. Treatment was paused in 23% of fractions to adjust for suboptimal breath hold or CW position. Conclusions: Electromagnetic confirmation of CW position is technically feasible, allowed verification of breath-hold reproducibility to within 3.2 mm (2SD) in 95% of fractions, and allows therapists to constrain beam-on time to the most reproducible and stable portion of each breath hold leading to a significant reduction in intrafraction motion during DIBH. With our technique DIBH during irradiation of left-breast cancer patients reduced the mean heart and LAD dose by at least 50%.

Scientific Abstract 2024; Table

Difference in CW position between port film and treatment  2SD CW excursion during breath hold CW excursion during beam-on

Lateral (LR) (mm)

Longitudinal (SI) (mm)

Vertical (AP) (mm)

0.1  2.5

0.1  3.1

0.1  2.3

2.5  2.3

5.0  4.0

4.2  2.8

1.1  1.2

1.7  1.4

1.3  0.9

Author Disclosure: M. Kathpal: None. B.A. Tinnel: None. C. Malmer: None. S. Ninneman: None. S. Wendt: None. G. Hughs: None. M. Gossweiler: None. D. Valentich: None. S. Buff: None. D.M. Macdonald: None.

2025 Correlation of Pathological Features of Ductal Carcinoma In Situ (DCIS) and Oncotype DCIS Score J. Wallach, S. Cate, S. Boolbol, I. Preeshagul, A. Gillego, A. Radzio, and M. Chadha; Mount Sinai Beth Israel Medical Center, New York, NY Purpose/Objective(s): The Oncotype DCIS score algorithm is derived from a composite of 12 genes, and it has been described as a prognostic factor in predicting subsequent risk of in-situ and invasive local recurrence. These observations were validated using a largely low-risk subset of patients enrolled in the ECOG 5194 trial. The objective of this study is to correlate the known pathologic prognostic features of DCIS with Oncotype DCIS score.

Materials/Methods: In a retrospective review of the breast database, we identified 72 patients diagnosed with DCIS and for whom the DCIS score was obtained. In addition to age, size of DCIS, nuclear grade (NG), presence of necrosis, and receptor status (ER/PR), we also recorded DCIS score in the 3 sub-categories low (0-38), intermediate (39-54), and high (>54). Results: The median age was 59.5 years (range 35-84 years). The median size of DCIS was 10.5 mm. NG distribution was NG1: 11.6%, NG2: 59.4%, and NG3: 29.0%. Necrosis was noted in 50.8% of cases. ER and PR status was positive (+) in 82% cases. Overall, mean DCIS score was 28.4 (range 0-85). Forty-six (63.9%) patients had low DCIS scores, 14 (19.4%) had intermediate scores, and 12 (16.7%) patients had high scores. Patients with size of DCIS  20 mm had a higher mean score of 36.0 compared to 21.5 in patients with DCIS size 10 mm size (p Z 0.0035).The mean DCIS score distribution by grade was 4.75 (NG1), 18.7 (NG2), and 54.2 (NG3), respectively. Patients with NG3 had significantly higher DCIS score compared to NG1/NG2 (p < 0.0001). The mean DCIS score was 35.8 in patients with necrosis and 16.3 in patients without necrosis (p Z 0.0005). Patients with ER + and PR + (n Z 53) DCIS had a mean score of 20.8, ER + PR - or ER - and PR+ (n Z 6) had a mean DCIS score of 50.5, and the score in ER- and PR- DCIS (n Z 7) was 62.9 (p Z 0.0019). In this study, we observed that well recognized low risk pathologic features in DCIS were consistently associated with DCIS scores in the low risk category. Conclusions: In this preliminary review, we observed that DCIS with known low-risk pathologic prognostic features frequently overlapped with low-risk category of DCIS scores. The added value of Oncotype DCIS score in the routine management of DCIS remains to be defined. Through carefully designed prospective trials, the role of DCIS score in administering risk-tailored therapy, in a cost-conscious health care environment are warranted. Author Disclosure: J. Wallach: None. S. Cate: None. S. Boolbol: None. I. Preeshagul: None. A. Gillego: None. A. Radzio: None. M. Chadha: None.

2026 Breast Radiation Therapy (RT) Using Simultaneous Integrated Boost (SIB): Which Is the Optimal Intensity Modulated RT (IMRT) Technique? Y. Abo-Madyan,1,2 M.M. Aly,3,4 L. Jahnke,1 F. Wenz,1 and G. Glatting3,1; 1 Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Mannheim, Germany, 2Department of Radiation Oncology and Nuclear Medicine, Faculty of Medicine, Cairo University, Cairo, Egypt, 3Medical Radiation Physics/Radiation Protection, Universita¨tsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany, 4Department of Radiotherapy and Nuclear Medicine, South Egypt Cancer Institute, Assiut University, Assiut, Egypt Purpose/Objective(s): To differentiate dosimetrically between different IMRT breast SIB techniques with regard to target coverage and organs at risk (OARs) exposure. Materials/Methods: Four inverse IMRT techniques were compared in CTdatasets of 12 breast cancer patients. Three techniques employ tangential based whole breast (PTV-breast) irradiation plus additional: two coplanar fields (T-2F), four non-coplanar fields (T-NC) or one volumetric modulated arc therapy (T-VMAT) directed only at the boost volume (PTV-boost). The fourth technique is a fully-modulated VMAT technique (f-VMAT). Various DVH parameters were used to compare the techniques. Delivery efficiency was analyzed based on number of monitor units (MUs) and estimated delivery time. Results: Overall, the four techniques produced plans with acceptable quality. The f-VMAT technique was significantly better than the other techniques in terms of boost target volume homogeneity index (1.02 vs 1.03 for the other 3 techniques, p < 0.001) and breast target volume heterogeneity index (p < 0.04) and V107% (10% vs w18% for the other 3 techniques, p < 0.001). F-VMAT resulted in significantly higher mean

International Journal of RadiatiOncology  Biology  Physics

S228 Scientific Abstract 2026; Table

Dosimetric parameters (mean  SD)

N Z 12 PTV-breast PTV-boost Ipsilateral Lung Contralateral Lung Contralateral Breast Heart (Lt.) Unspecified Tissue

T-2F V95 (%) Heterogeneity Index (D2%/D98%) V95 (%) mean (Gy) mean (Gy) mean (Gy) V30 (%) mean (Gy) low dose spillage index (V5/Breast Volume)

cardiac doses in right-sided cancer patients (2.6 Gy vs < 1.9 Gy for the other 3 techniques, p < 0.003), contra-lateral lung and contra-lateral breast mean doses and MUs (1015 MU vs < 424 MU for the other three techniques, p < 0.001). F-VMAT had the lowest “prescribed dose spillage” outside the respective targets but the highest “low dose spillage” to nearby OARs. T-2F resulted in significantly lower V95% in PTV-boost compared to other techniques (p < 0.009). T-NC had significantly lower mean contralateral OAR dose (p < 0.05) (Table). The estimated beam-on time was similar in all techniques (between 2.8  0.5 and 3.3  1.5 min) however T-NC would practically require more setup and overall treatment time. Conclusions: While all techniques produced plans of acceptable quality, the VMAT techniques, f-VMAT and T-VMAT, offered the best target coverage. F-VMAT increases the low dose spillage so that its use would only be justified when cardiac dose (V30) is critically high. T-VMAT would be considered the technique of choice for most patients due to its robustness, practicality and offering a most balanced mix between homogenous and sufficient target coverage on one side versus dose scatter to the OARs on the other. T-NC although dosimetrically marginally better than T-VMAT, puts more load on setup accuracy and machine time due to complexity. Author Disclosure: Y. Abo-Madyan: A. Employee; University Medical Center Mannheim, University of Heidelberg. F. Honoraria; Zeiss, Merck. M.M. Aly: E. Research Grant; Deutscher Akademischer Austausch Dienst (DAAD e German Academic Exchange Service). L. Jahnke: A. Employee; University Medical Center Mannheim, University of Heidelberg. F. Honoraria; Elekta. G. Consultant; Elekta. H. Speakers Bureau; Elekta. I. Travel Expenses; Elekta. F. Wenz: A. Employee; University Medical Center Mannheim, University of Heidelberg. E. Research Grant; Elekta, Zeiss. F. Honoraria; Elekta, Zeiss, Celgene, Roche, Lilly, Ipsen. G. Consultant; Elekta. I. Travel Expenses; Elekta, Zeiss, Celgene, Roche, Lilly, Ipsen. K. Advisory Board; Elekta, Celgene. Q. Patent/License Fee/ Copyright; Zeiss. G. Glatting: A. Employee; University Medical Center Mannheim, University of Heidelberg. E. Research Grant; grant by the Federal Ministry of Education and Research, and Bundesamt fu¨r Strahlenschutz (Federal Office for Radiation Protection), for the establishment of professorship.

Scientific Abstract 2027; Table

Year of Radiation therapy

Year of Radiation therapy

94.5 1.36 95.9 8.4 0.9 1.1 1.3 3.0 1.42

        

1.8 0.03 2.4 1.6 0.2 0.3 1.4 0.9 0.26

T-NC 94.6 1.37 98.0 8.8 0.7 0.9 1.0 2.8 1.31

        

T-VMAT

1.9 0.01 0.9 1.5 0.1 0.2 0.9 0.6 0.19

95.5 1.35 99.3 9.1 1.1 1.2 1.2 3.5 1.38

        

2.3 0.01 0.6 1.5 0.2 0.3 1.4 1.0 0.25

f-VMAT 96.6 1.30 98.6 9.5 1.8 1.8 0.0 4.2 2.65

        

1.6 0.02 1.7 0.9 0.3 0.4 0.0 0.4 0.55

2027 Adoption of Intensity Modulated Radiation Therapy (IMRT) in Early-Stage Breast Cancer Patients Receiving Hypofractionated and Conventionally Fractionated Radiation in the United States A. Falchook,1 L.H. Hendrix,1 H.A. Curry,2 R.C. Chen,3 and R. Jagsi4; 1 University of North Carolina, Chapel Hill, NC, 2Eviti, Philadelphia, PA, 3 University of North Carolina at Chapel Hill, Chapel Hill, NC, 4University of Michigan, Ann Arbor, MI Purpose/Objective(s): Large randomized trials have demonstrated the non-inferiority of hypofractionated RT (HyRT) to the whole breast compared to conventional fractionation for many patients with early-stage breast cancer. Uptake of HyRT should represent cost-savings to the health care system, but these savings might be offset if providers are more likely to deliver HyRT using IMRT. We sought to evaluate the hypothesis that providers might preferentially use IMRT in HyRT courses, in an attempt to minimize the impact of higher doses per fraction to normal tissues. Therefore, we examined patterns of IMRT uptake in the US for breast cancer patients receiving HyRT and conventionally fractionated RT in recent years. Materials/Methods: A total of 21,211 women in the SEER-Medicare database with pTis-pT2 N0 M0 breast cancer who received lumpectomy followed by external beam radiation therapy from 2004-10 were included. Medicare claims were used to determine which patients received IMRT and the fractionation used: HyRT (13-24 treatments), conventional (25+ treatments). Bivariable and multivariable analyses were used to evaluate factors associated with receipt of IMRT. Results: On a background of increasing HyRT use over time, IMRT utilization increased, both in patients receiving HyRT and conventional RT (Table). By 2009-10, 22.7% of HyRT patients and 23.0% of conventional RT patients received IMRT. On multivariate analysis, later RT year (OR Z 3.49 for 2009-10 compared to 2004, p < 0.001) and left sided tumor (OR Z 1.45, p < 0.001) were associated with increased IMRT, with significant regional variation in use. Fractionation scheme (HyRT vs conventional) was not associated with IMRT (p Z 0.34), nor were age, race, comorbidity status, tumor grade, T stage, or regional education and income levels.

IMRT use in hypofractionated and conventionally fractionated RT Hypofractionated Radiation therapy

Not IMRT, N (%)

Received IMRT, N (%)

2004 2005 2006 2007 2008 2009-2010 Conventional Fractionation 2004 2005 2006 2007 2008 2009-2010

99 (90.0) 109 (80.7) 110 (84.6) 141 (79.2) 255 (81.7) 437 (77.3) Not IMRT, N (%) 2458 (90.9) 2897 (85.6) 2775 (84.1) 2594 (82.2) 2369 (79.2) 2763 (77.0)

11 (10.0) 26 (19.3) 20 (15.4) 37 (20.8) 57 (18.3) 128 (22.7) Received IMRT, N (%) 247 (9.1) 487 (14.4) 525 (15.9) 560 (17.8) 621 (20.8) 825 (23.0)

P Z 0.04

P < 0.001