ESTRO 2023 - Abstract Book

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ESTRO 2023

with MHD was 0.50 (p=0.025) and 0.645 (p=0.002) for CCDax and CCDtf respectively indicating moderate positive correlation, with a better correlation for CCDtf [Figure 2]. CCDax ranged between 1.56 cm to 10cm, with a median of 7.52cm. CCDtf ranged between 0 to 7.4 cm, with a median of 2.3cm. CCDtf was ≤ 2cm in 9 (45%), ≤ 4cm in 17 (85%) and >4cm in 3 (15%) patients. There was no correlation between inspiratory volume threshold and MHD; Pearson correlation coefficient -0.082 (p=0.732).

Conclusion In-field axial cardiac contact distance in breath-hold scan (CCDtf) correlates with mean heart dose achieved. This can be used as a surrogate measure to check the adequacy of breath-hold benefit while planning left-sided breast cancer radiotherapy. Patients with inadequate breath-hold might benefit from alternate planning techniques such as rotational IMRT/VMAT/proton therapy and more research on this is warranted.

PO-1283 Correlation between cardiac rotation and LAD Artery dose In breast cancer radiation therapy

Abstract withdrawn

PO-1284 Comprehensive analysis to predict lymphedema after salvage irradiation in locoregional breast cancer

H. Shin 1 , H. Kim 1 , W.K. Cho 1 , N. Kim 1 , W. Park 1

1 Samsung Medical Center, radiation oncology, Seoul, Korea Republic of

Purpose or Objective Regarding salvage radiation therapy (RT) for breast cancer, lymphedema is one of the most concerning complications. However, optimal dose constraints to minimize subsequent arm lymphedema (SAL) are not well studied. This study aimed to identify risk factors for SAL including dosimetric parameters in patients treated with salvage repeated RT for locoregional breast cancer. Materials and Methods We retrospectively reviewed 65 patients who received salvage repeated RT for locoregional recurrent breast cancer between 2003 and 2017. Regional nodal areas were divided into 7 distinct subregions and retrospectively contoured per atlas suggested by Gross et al (Int J Radiat Oncol Biol Phys, 2019). Initial and repeated RT plans for each patient were deformed and merged to calculate dose-volume histogram at nodal area. Dosimetric analysis was performed using EQD2 dose of Dmax, Dmean, Dmin, V30Gy, V40Gy, V45Gy, and V50Gy, V60Gy of each subregion. Maximally selected rank statistics were used to identify optimal cut points of dosimetric variables. Multivariate Cox proportional hazard regression and Akaike information criterion model were used to identify optimal model to predict SAL. Results Salvage repeated RT was combined with salvage surgery in 34 patients (52.3%) and salvage taxane-based chemotherapy was administered in 29 patients (44.6%). Total number of RT course were 2 in 59 patients (90.6%) and 3 in 6 (9.4%). Median EQD2 of accumulated prescription dose was 113.0 Gy (interquartile range [IQR] 105.0-121.6). Salvage RT modalities were 3DCRT/electron in 28 patients (43.1%), IMRT in 26 patients (40.0%), and proton beam therapy in 11 patients (16.9%). With a median follow-up of 30.4 months (IQR 19.3-52.5), 15 patients (23.1%) experienced SAL with a median interval of 6.43 months (IQR 13.3-16.5) after secondary RT. Patients with SAL frequently received salvage taxane-based chemotherapy and higher dose to axillary-lateral thoracic vessel junction (ALTJ), lateral to ALTJ, supraclavicular/superior-medial, and superior-lateral region compared with patients without SAL. In multivariate analysis for SAL without dosimetric parameters, salvage taxane-based chemotherapy remained significant (Hazard ratio [HR], 4.19; P= 0.041). After incorporating dosimetric parameters, an final optimal model selected lateral to ALTJ V30Gy ≥ 55.8% (HR 5.35; P = 0.001) and salvage taxane-based chemotherapy (HR, 4.73; P = 0.021).

Conclusion