ESTRO 38 Abstract book

S167 ESTRO 38

scars treated with perioperative interstitial high dose rate (HDR) brachytherapy. Material and Methods The patient cohort under study comprised 61 keloids in 51 patients. All keloid lesions were treated with 12Gy in 4 fractions, during 48h, i.e., one fraction every 12h. The treating physician inserted a catheter along the scar during the surgical procedure, which served for the delivery of the subsequent brachytherapy fractions. The lapse of time between surgery and brachytherapy was less than 90 minutes. Local failure was defined as recurrence of the apparent keloid as well as symptoms at the same location. The median age of the patients was 46 years (20-89 years). Keloids had an average size of 6.3cm and were located on the chest (41%), ear lobe (21%), back (1.6%), and extremities (11.5%). The IBM SPSS v.24 software was used for statistical analysis of quantitative variables (Analysis of Variance, ANOVA test) and qualitative variables (Chi- square test), such as the scar size or patient’s race. P- value ≤ 0.05 was taken as significant. Results The recurrence rate, with a median follow-up of 48 months (range 1-96 months), was only of 4.9%, all of them located on the chest. In addition, most patients with successful treatment presented an excellent cosmetic result at the scar location, except some patients (below 20%) for which a small part of the scar remained but no pain, stinging or tissue thickening was reported. The ANOVA and Chi-square tests showed no significant statistical relationship between the recurrence rate and the race (p=0.312), or the size of the scar (p=0.525). Figure 1 illustrates the cosmetic outcome in one of the patients with a keloid scar located in the ear lobe, before (Figure 1.a) and after treatment (Figure 1.b).

applicators and 0.82 [95% CI: 0.80–0.85] for the 3D-prints (p<0.01,Fig. 2) Dosimetry: TLD measurements for both types of applicators agreed with the expected doses predicted by the TPS within a local tolerance of ±5%. Conclusion The applicators made using the digitally designed 3D printing process were more geometrically accurate compared with the applicators made using the current traditional fabrication process. Both types of applicators gave satisfactory dosimetric performance. The 3D-printing process is faster and less labour intensive. The resulting applicators are durable, lightweight, low cost and visually appealing. They can be easily reprinted for teaching or further studies. As a result of this study digitally designed 3D-printed HDR skin applicators will be incorporated into our routine clinical practice.

[1] Ricotti, R et al. 2016. 3D-printed applicators for high dose rate brachytherapy: Dosimetric assessment at different infill percentage. Physica Medica, 32(12),p.1698-1706 [2] Jones, EL et al. 2017. Introduction of novel 3D- printed superficial applicators for high-dose-rate skin brachytherapy. Brachytherapy ,6(2),p.409-414 OC-0323 Perioperative interstitial high dose rate brachytherapy for keloids scars V. Vera Barragam 1 , M. De Juan Marín 2 , S. Blanco Parajón 1 , J. Fernández García 3 , G. Juan Rijo 1 , A.I. Alonso García 1 1 Hospital Universitario Central de Asturias, Radiotherapy oncolgy, Oviedo, Spain ; 2 Hospital Universitario Central de Asturias, Plastic Surgery, Oviedo, Spain; 3 Hospital Universitario Central de Asturias, Phisics, Oviedo, Spain Purpose or Objective The treatment of keloid scars is still a clinical challenge due to their high recurrence rate, which can happen in up to 30% of the cases. The use of radiation therapy combined with surgical excision is considered as one of the most effective treatments. However, there is little consensus among the medical community about the most optimal treatment in terms of dose, fractionation, and type of treatment: external or internal, i.e. brachytherapy. This study evaluates the treatment outcome in terms of local control, as well as from a cosmetic point of view, of keloid

Conclusion Perioperative interstitial HDR brachytherapy appears to be a high effective treatment against keloid scars, with a decreased recurrence rate below 5%. All failed treatments happened in the chest, which suggests the investigation of higher dose for this site. The treatment was well tolerated by all patients and did not present significant side effects. The cosmetic results were also excellent and the patients reported great satisfaction after treatment.

Presidential Symposium: Presidential symposium

SP-0324 Umberto Ricardi 1 1 University of Turin,Turin, Italy

Abstract not received

Award Lecture: Claudius Regaud Award Lecture

SP-0325 Is fractionation history? D. De Ruysscher 1