ESTRO 2021 Abstract Book

S43

ESTRO 2021

including level I or not. For 62 randomly selected pts (5% or ≥3 pts per Swedish RT-site), the CTVs for individual axillary levels were redelineated according to ESTRO guidelines. ESTRO-based delineations were also available in 210 Danish pts. Results In Swedish pts, the CTV included only breast/chest wall in 4% (n=36), breast/chest wall and level I-IV in 40% (n=332), breast/chest wall and level II-IV in 56% (n=465), or only level I-IV in 0.1% (n=1). In Danish pts, the corresponding figures were breast/chest wall and level I-IV in 51% (n=154), and breast/chest wall and level II- IV in 49% (n=148). In Swedish pts, there was no difference regarding inclusion of level I between randomized groups (39% vs. 41%, p=0.5). In Danish pts, the CTV included level I in 14% of those receiving ALND, and in 97% of pts in the surveillance group. Dose coverage data for the 62 SE pts and 210 DK pts with level I delineated are shown in table 1. Even when level I is not included as a planning target, it still receives significant dose in both Sweden and Denmark. Figure 2 shows a full dose-volume histogram for the Swedish patients only, further detailing the relatively small change in dose distribution to level I regardless if included in the CTV or not.

Conclusion In Swedish SENOMAC pts no difference in target volumes was seen between randomized groups. In Denmark, level I was included in the surveillance group but not in case of ALND. This analysis shows, however, that regardless of inclusion in the original CTV, level I receives high dose coverage from adjacent fields through RT to the breast/chest wall and level II-IV. Hence, differences in axillary RT target volumes between randomized groups should not significantly confound the interpretation of survival analyses. OC-0070 Patient-reported symptoms of late radiation toxicity in breast cancer patients D. Mink van der Molen 1 , M. Batenburg 1 , A. Doeksen 2 , T. van Dalen 3 , E. Schoenmaeckers 4 , R. Bijlsma 5 , A. Witkamp 6 , M. Ernst 7 , M. Sier 8 , W. Maarse 9 , D. van den Bongard 10 , F. van der Leij 11 , H. Verkooijen 1 1 University Medical Centre Utrecht, Division of Imaging and Oncology, Utrecht, The Netherlands; 2 St. Antonius Hospital, Department of Surgery, Utrecht, The Netherlands; 3 Diakonessenhuis Utrecht, Department of Surgery, Utrecht, The Netherlands; 4 Meander Medisch Centrum, Department of Surgery, Amersfoort, The Netherlands; 5 University Medical Centre Utrecht, Department of Medical Oncology, Utrecht, The Netherlands; 6 University Medical Centre Utrecht, Department of Surgery, Utrecht, The Netherlands; 7 Alexander Monro Ziekenhuis, Department of Surgery, Bilthoven, The Netherlands; 8 Ziekenhuis Rivierenland, Department of Surgery, Tiel, The Netherlands; 9 University Medical Centre Utrecht, Department of Plastic, Reconstructive and Hand Surgery, Utrecht, The Netherlands; 10 Amsterdam University Medical Centre, Department of Radiation Oncology, Amsterdam, The Netherlands; 11 University Medical Centre Utrecht, Department of Radiation Oncology, Utrecht, The Netherlands Purpose or Objective To assess the prevalence of patient-reported symptoms of late radiation skin toxicity (LRT) in breast cancer patients and to determine the association between LRT and quality of life. Materials and Methods Within the prospective UMBRELLA cohort, a survey on self-reported LRT was sent to breast cancer patients with > 12 months interval since radiotherapy with curative intent. Symptoms of LRT were evaluated on a 4- point Likert scale. Based on the CTCAE version 4.03 and RTOG, LRT was defined as grade 3-4 (moderate- severe) breast or chest wall pain in combination with at least one other grade 2-4 (mild-severe) LRT symptom, i.e. breast or arm/hand lymphedema, firmness of the breast or impaired arm movement. Physical, role and