ESTRO 37 Abstract book

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ESTRO 37

the safety of this regimen. Its actual effectiveness will be tested in a longer follow-up. EP-1304 Patterns of loco-regional failure in early breast cancer treated by WBRT in lateral position H. XU 1,2 , B. Estelle 1 , C. Emilie 1 , K. Samar 1 , L. Christelle 1 , B. Louis 1 , F.B. Nathalie 1 , B. Anne 1 , F. Alain 1 , K. Youlia M. 1 1 Institut Curie, Radiation Oncology, Paris, France 2 Ruijin Hospital- Shanghai Jiaotong University School of Medicine, Radiation Oncology, Shanghai, China Purpose or Objective To evaluate loco-regional control and describe the patterns of failure in patients (pts) with breast cancer irradiated by previously published whole breast radiotherapy (WBRT) in the isocentric lateral decubitus position (ILD). Material and Methods We studied 832 consecutive female patients with early stage BC treated by breast conservative surgery (BCS) followed by 3D conformal WBRT-ILD between 2005 and 2010. All patients who experienced loco-regional recurrence have been studied. Five-year RFS and OS rate were calculated. Mapping patterns of regional recurrences was also performed. Results Among the 832 women included 51% of the patients presented left side BC and 49% right. The median age was 61.5 years (range, 29-90). Different types of fractionation schemes were used: 66 Gy in 33 fractions (fr) (46.5%), 50Gy/25 fr (17.9%), 40Gy/15 fr or 41.6Gy/13 fr (26.1%) and 30Gy/5 fr (9.5%). With the median follow-up of 6.4 years, only 36 locoregional recurrences were observed without any association with the fractionation regimen (p=0.2). In the population of 36 pts, 28 cases (77.8%) presented with "in breast" local recurrences (LR), 2 cases (5.6%) with LR and regional lymph node recurrence (RLNR), and 6 cases (16.6%) with RLNR alone (in non- irradiated areas). The median latency recurrence time was 50 months. Complete cartography of the recurrences was realized and in the most cases the LR was situated close to the initial tumor bed. The LR cases showed a significantly lower metastasis rate, P<0.001 ， and had a significantly long overall survival in comparison with the patients with RLNR. However, multivariate Cox regression analysis showed the recurrences site had no significant impact on the overall survival (P=0.14). Conclusion The presented results are excellent in terms of LR rate. Further careful follow-up and careful registration of the recurrences is needed to improve their understanding. EP-1305 Location of arm draining lymph node in relation to breast cancer radiotherapy field and volume W. Wang 1 , R. Ward 1 , D. Jia 1 , S. Ashworth 1 , E. Estoesta 1 , T. Moodie 1 , R. McCredie 2 , V. Ahern 1 , K. Stuart 1 , N. Ngui 3 , J. French 3 , E. Elder 3 , D. Farlow 4 1 The Crown Princess Mary Cancer Center Westmead, Department of radiation oncology, Westmead, Australia 2 The Crown Princess Mary Cancer Center Westmead, Department of medical physics, Westmead, Australia 3 Westmead Breast Cancer Institute, Department of Surgery, Westmead, Australia 4 Westmead Hospital, Department of Nuclear Medicine, Westmead, Australia Purpose or Objective Axillary reverse mapping (ARM) is a technique used to identify the lymph node draining the arm (ARM node). Our study aim was to examine the location of the ARM nodes in relation to target volumes and treatment fields for breast cancer radiotherapy. Material and Methods 18 breast cancer patients underwent lymphoscintigraphy of contralateral arm (left 10, right 8) and SPECT CT scan

on a research study. Patient position for the SPECT CT scan approximated the position used for radiotherapy. Using MIM software, the ARM node for each subject was contoured on the SPECT CT and verified by a nuclear medicine physician. The CT component of the SPECT CT was then transferred to ECLIPSE radiotherapy planning software, and breast and axilla were contoured on this CT scan according to the ESTRO contouring guideline. Two radiotherapy plans were generated for each subject using standard tangential IMRT technique at a dose of 50 Gy in 25 fractions, one treating breast alone, the other treating breast and axilla level 1-4. The ARM node was considered 'within the radiotherapy field” if the mean dose received by the ARM node was more than 50% of the prescribed dose: i.e. 25 Gy. Results One right-sided subject had 2 ARM nodes, all others had 1 ARM node. All ARM nodes (left 10, right 9) were located within level 1 of the axilla. For the subject with 2 ARM nodes, the node that received higher dose was used for the analysis. The mean dose received by the ARM node in the whole breast radiotherapy plans ranged from 0.8 - 45.5 Gy, with a median of 10.9 Gy. The mean dose received by the ARM node in the whole breast and axilla plans ranged from 43.4 - 52.5 Gy, with a median of 49.3 Gy. In the whole breast radiotherapy plans, only 5 out of 18 ARM nodes were found to be 'within radiotherapy field’, and only 2 ARM nodes received more than 40 Gy. In the breast and axilla plans, all 18 ARM nodes were 'within radiotherapy field”. To better visualise the locations of ARM nodes, all left sided ARM nodes were then mapped onto a CT set from one of the left-sided subjects, and all the right sided ARM nodes mapped onto one of the right-sided subjects, and digitally reconstructed radiograph (DRR) for radiotherapy fields were produced. The DRR of Lateral tangential field in the whole breast radiotherapy plan was shown in image 1, and DRR of the anterior oblique axillary field in the breast and axilla radiotherapy plan was shown in image 2. In the DRRs, the ARM nodes were shown in blue, the two ARM nodes belonging to the same patient were shown in red.

Conclusion Our study demonstrates that the vast majority of ARM nodes (72%) are outside the tangential whole breast radiotherapy fields, whereas previous studies have shown that the majority of sentinel nodes of the breast are located within the tangential breast radiotherapy fields. In our study, all the ARM nodes were within the axillary