ESTRO 2023 - Abstract Book

S634

Monday 15 May 2023

ESTRO 2023

Measurements were performed at baseline, after the intensive phase, after 1, 3, 6 months of maintenance phase, and after 6 months of follow-up. Results Results: In all three groups, excessive lymphedema volume decreased significantly after three weeks of intensive treatment (p< 0.001). No differences between the fluoro-MLD group (mean absolute reduction of 5.3 (95% CI: 3.9 -6.7) percentage points of % excessive volume representing a relative reduction of 23.3%) and the traditional MLD group (mean absolute reduction of 5.2 (95%CI 3.8-6.6) percentage points of % excessive volume, which is a relative reduction of 20.9%) (mean difference between groups: 0.0% (95% CI: -2.0; 2.1, p=0.890), or between the fluoro-MLD group and the placebo MLD group (mean absolute reduction (95% CI) or 5.4 (95%CI: 4.0-6.8) percentage points of % excessive volume, or a relative reduction of 24.8%) (mean difference between groups (95% CI): -0.2% (-2.1; 1.8, p=0.826) were found. An increased fluid accumulation at the level of the shoulder/trunk was present in all three treatment groups, however, this was not significantly different between the groups (p>0.0125) (mean difference between the fluoro-MLD and traditional MLD group (95% CI): -3.6% (-6.4; -0.8), p= 0.013; mean difference between fluoro-MLD and placebo-MLD group (95% CI): -2.4% (-5.2; 0.4, p=0.101)) Conclusion Conclusions: In patients with chronic BCRL, evidence for a benefit of MLD in addition to the other components of DLT could not be demonstrated. There is no indication to still prescribe and include time-consuming MLD in the treatment of BCRL. OC-0768 Breast induration and irradiated volume in the DBCG HYPO trial: The importance of age and smoking M.S. Thomsen 1 , J. Alsner 2 , C.M. Lutz 1 , M. Berg 3 , I. Jensen 4 , E.L. Lorenzen 5 , D.S. Møller 1 , H.M. Nielsen 6 , E.H. Jakobsen 7 , L. Stenbygaard 8 , M.H. Nielsen 9 , M. Jensen 10 , J. Overgaard 2 , B.V. Offersen 11 1 Aarhus University Hospital, Department of Medical Physics, Aarhus, Denmark; 2 Aarhus University Hospital, Department of Experimental Clinical Oncology, Aarhus, Denmark; 3 University Hospital of Southern Denmark, Department of Medical Physics, Vejle, Denmark; 4 Aalborg University Hospital, Department of Medical Physics, Aalborg, Denmark; 5 Odense University Hospital, Laboratory of Radiation Physics, Odense, Denmark; 6 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark; 7 University Hospital of Southern Denmark, Department of Oncology, Vejle, Denmark; 8 Aalborg University Hospital, Department of Oncology, Aalborg, Denmark; 9 Odense University Hospital, Department of Oncology, Odense, Denmark; 10 Copenhagen University Hospital, Rigshospitalet, Danish Breast Cancer Group, Copenhagen, Denmark; 11 Aarhus University Hospital, Department of Oncology, Aarhus , Denmark Purpose or Objective To investigate the association between irradiated breast volume and breast induration grade 2-3 at 3 years after radiation therapy (RT) in the phase III randomized Danish Breast Cancer Group (DBCG) HYPO trial (NCT00892814) [1] and the importance of patient age and smoking. Materials and Methods In the international DBCG HYPO trial, patients (pts) >40 years being candidates for whole breast irradiation (WBI) were randomized to either 50Gy in 25 fractions or 40Gy in 15 fractions. For this analysis, pts receiving boost were omitted (incl. all pts <50 years). Thus, the study included the 1,305 Danish pts treated without boost. During the accrual 2009-2014, RT plans for the Danish pts were stored in the Danish national RT data bank and the volume of the breast covered with various dose levels was determined. Irradiated breast volume was defined as the volume with D ≥ 50Gy or D ≥ 40Gy in the 50Gy and 40Gy arm, respectively. Model of breast induration according to breast volume irradiated was developed based on individual pt data using logistic regression and stratified by treatment arm, age groups (50-64 vs 65+), and smoking status (never/prior vs current). Results RT plans from 1,297 pts (50Gy: 655; 40Gy: 642) from four Danish RT centers were analyzed, and of these 1,131 pts (50Gy: 560; 40Gy: 571) had an induration score at 3 years. A volume effect for risk of induration has previously been described in the DBCG Partial Breast Irradiation (PBI) trial including pts age ≥ 60 years and not receiving boost [2]. Due to the variation in age distribution in the two trials, age-stratified models were applied to the 40Gy pts in the HYPO trial and the WBI arm of the PBI trial (Figure 1). Both trials show that the previously described volume effect is restricted to pts ≥ 65 years, whereas there is no association between irradiated volume and risk of induration in pts aged 50-64 years. In the HYPO trial, models stratified on treatment arm show a similar volume effect in the two arms in pts ≥ 65 years and a lack of volume effect in pts aged 50-64 years but with a slightly lower risk overall in the 40Gy arm (Figure 2). When stratifying models on smoking, the frequency of induration was a factor of two higher for current smokers than for never/prior smokers independent of the irradiated breast volume and age (Figure 2). NCT02609724, EudraCT 2015-004822-33