ESTRO 36 Abstract Book

S511 ESTRO 36 _______________________________________________________________________________________________

Image-guided radiation therapy using MV imaging can be incorporated into the treatment plan to give clinically acceptable dose distributions. Dose to normal tissues is increased, however, and depends on the imaging technique, it is important to select the technique which minimizes normal tissue dose while providing sufficient image quality for patient setup.

same score, 36% had a better final score, and 4.4% had a worse final score. Patient age, tumor location, tumor size, number of catheters, V100 (volume receiving 100% of the prescription dose), V150 (volume receiving 150% of the prescription dose), DNR (dose non-uniformity ratio), and skin D max (maximum skin dose) were correlated with the final cosmetic scores and with the change in cosmetic scores between both photographs. Only lower DNR values (0.3 vs 0.26; p=0.009) were significantly associated with improved cosmetic outcome vs same/worse cosmetic outcome.

Poster: Brachytherapy: Breast

PO-0922 Late toxicity and cosmetic outcome following APBI using interstitial multicatheter HDR brachytherapy T. Soror 1,2 , G. Kovács 2 , N. Seibold 2 , C. Melchert 2 , K. Baumann 3 , E. Wenzel 4 , S. Stojanovic-Rundic 5 1 National Cancer Institute, Radiation Oncology Department, Cairo, Egypt 2 Interdisciplinary Brachytherapy Unit, University of Luebeck/UKSH-CL- Germany, Lübeck, Germany 3 Clinic for Gynecology and Obstetrics, University of Luebeck/UKSH-CL- Germany, Lübeck, Germany 4 Clinic for Plastic Surgery, University of Luebeck/UKSH- CL- Germany, Lübeck, Germany 5 5Institute for Oncology and Radiology IORS, Radiation Oncology Department, Belgrad, Serbia Purpose or Objective Accelerated partial breast irradiation (APBI) has became a valid option in treating patients with early stage breast cancer following breast conservation surgery (BCS). This work reports on the late toxicity and the cosmetic outcome following APBI using interstitial multicatheter HDR intensity modulated brachytherapy (HDR-IMBT). Material and Methods Between 2006 and 2014, 114 patients received adjuvant APBI using interstitial multicatheter HDR-IMBT. Late toxicities were reported according to both the RTOG/EORTC score and the LENT/SOMA score. Cosmetic changes were documented by taking digital photographs before the APBI and during each follow-up visit. For each patient, we assessed two photographs, the first was taken after surgery and before APBI (baseline image), and the second at the last available follow-up visit. The cosmesis was assessed through a multidisciplinary team using the Harvard breast cosmesis scale. The clinical and the dosimetric parameters were investigated for any potential correlations with the cosmetic results.

Conclusion APBI using interstitial multicatheter HDR-IMBT adjuvant to BCS results in acceptable rates of late toxicity and cosmetic outcome. Deterioration in the breast cosmetic scores occurs in less than 5% of the patients. The final breast cosmetic outcome seems to be mainly influenced by the cosmetic result of the surgery. Lower DNR value is significantly associated with better cosmetic outcome. PO-0923 Does catheter entry-exit dosimetry correlate with grade of skin marks after breast brachytherapy? T. Wadasadawala 1 , R. Krishnamurthy 1 , U. Gayake 1 , R. Phurailatpam 1 , S. Paul 1 , R. Sarin 1 1 Actrec-Tata Memorial Centre, Radiation Oncology, Navi Mumbai, India Purpose or Objective Grade of post-implant skin marks after multi-cathetar interstitial brachytherapy (MIB) is an important factor in determining cosmesis. This study intends to establish the correlation if any between catheter entry-exit (E-E) dosimetry and grade of skin marks at the E-E sites. Material and Methods Visibility of the post implant E-E catheter marks was noted plane-wise for 25 patients (173 planes) with minimum 18 months follow-up post implant. All patients were treated with 34 Gy in 10 fractions, twice a day at minimum 6 hours apart. These were graded as 'not visible', 'faint', 'clear' and 'prominent'. Dose received by the skin at the E-E sites was calculated from the treated plans which were retrieved from the Oncentra treatment planning system (Figure 1). Dose maximum (Dmax) for each plane was determined meticulously. Closest distance of each E-E point in each plane from the respective first or last dwell position, clinical target volume (CTV) and the reference isodose (85%) was measured. Statistical analysis was done in IBM SPSS version 21. Correlation between quality of implant marks and dosimetric parameters was analyzed using Spearman’s co-efficient (single tailed). Chi square test was done between the quality of marks and plane Dmax as well as closest distances each from CTV, prescription isodose and first or last dwell position. ROC curve was used to determine dose constraints.

Results The median follow-up period was 3.5 years (range 0.6 – 8.5). Late skin/soft tissue toxicities at the last follow-up visit are listed in Table1. Ten patients had grade-3 toxicity (8.8%) and no patients showed grade-4 toxicity. The most common toxicities were fibrosis (56.2% by LENT/SOMA score, and 47.4% by RTOG/EORTC score) followed by pain (42.1%). The final cosmetic scores were 81.5% excellent/good and 18.5% fair/poor. Comparing both the baseline and the last follow-up cosmetic scores, 59.6% of the patients had the