ESTRO 2021 Abstract Book

S1685

ESTRO 2021

evaluated. Results Information in PROs and medical records was overall consistent concerning acute toxicity to radiotherapy. However, acute toxicity was often documented in the medical record prior to completion of the PRO questionnaire. Documentation of the consultations in the medical records was seemingly not based on the PRO questionnaire. Information in the PROs indicated decreased mental well-being compared with documentation in the medical records. Conclusion Patients completed the PRO questionnaire weekly, but the medical record review indicated that PRO data were not used in consultations. Thus, the PRO questionnaire did seemingly not support patient-centered communication. Acute toxicity to radiotherapy was mainly identified in the daily meetings between patients and healthcare professionals in the radiotherapy clinic. However, the PRO questionnaire has the potential to identify issues related to patients' mental well-being, which may support a patient-centered dialouge if further implemented in the clinical workflow. PO-1981 Dosimetric predectifs factors of acute skin toxicity after hypofractionated breast irradiation M. bohli 1 , R. Ben Amor 1 , D. Aissaoui 1 , J. Yahyaoui 2 , A. Hamdoun 2 , L. Kochbati 1 1 Faculty of Medicine_Tunis El Manar Univerity/Abderrahman Mami Hospital, Radiation Oncology, Ariana, Tunisia; 2 Abderrahman Mami Hospital, Radiation Oncology, Ariana, Tunisia Purpose or Objective The aim of this study was to evaluate acute skin toxicity in early breast cancer patients treated with hypofractionated whole breast radiotherapy (HF-WBRT) after breast conserving surgery and to analyze their correlation with dosimetric parameters. Materials and Methods We retrospectively evaluated 201 breast cancer patients treated with 3D HF-WBRT after breast conserving surgery between August 2017 and December 2019. The prescribed dose was 40.05 Gy in 15 fractions to the whole breast followed by 13.35 Gy in 5 fractions to tumor bed. The median age was 53 years (25-82 years). Tumor was classified T1 and T2 in respectively 55% (n=111) and 45% (n=91). The dosimetric parameters including: the breast volume, boost volume, the volume of the breast receiving 95%, 105% and 107% of the prescribed dose (V95%, V105% and V107%) and the maximum dose (Dmax) were analyzed. Acute skin toxicity during RT was recorded, according to The Common Toxicity Criteria for Adverse Events scale (CTCAE) version 4.0. The correlation between the incidence of skin toxicity and its grading with dosimetric parameters was performed with the χ2 test. Results There was no erythema in 9%, grade 1 erythema in 64.5%, grade 2 in 24% and grade 3 in 2.5%. No grade 4 erythema was observed. The median breast volume was 693.80 cc (100-2777cc). The median boost volume was 14.65cc (1.86-201cc).The median breast volume receiving 95%, 105% and 107% of prescribed dose was 683cc (99.8-2664cc), 48 cc (0-1140cc) and 0.017cc (0- 732cc) respectively. The mean breast volume, boost volume and V95% were significantly higher in patients with acute skin toxicity Grades 2-3 than in patients with skin toxicity Grade 0-1 (p=0.000, p=0.02 and p=0.000 respectively). Positive correlation was found between Grade 2-3 skin and breast volume > 800cc (p=0.000), boost volume > 18cc (p=0.002), V105% > 40cc (p=0.03) and Dmax >56Gy (p=0.007). Conclusion We identified 105 % of the prescribed dose as a cut off for Dmax with a volume less than 40 cc as parameters to minimize acute skin toxicity in hypofractionated radiotherapy for breast cancer. PO-1982 Dosimetric and clinical outcome in image guided interstitial brachytherapy for cervical stump cancer F. GUILLEMIN 1 , P. POMMIER 2 , A. SERRE 2 , F. GASSA 2 , N. SANDT 2 , F. LAFAY 2 1 Centre Jean Perrin, Radiotherapy, Clermont-Ferrand, France; 2 Centre Léon Bérard, Radiotherapy, Lyon, France Purpose or Objective According to the European guidelines for cervix cancers, management of cervical stump cancers should follow the recommendations of patients without previous subtotal hysterectomy, but may necessitate an adaptation of the radiotherapy modalities especially for brachytherapy (BT). However, data with modern BT technics are very scarce. Materials and Methods From May 2013 to March 2020, 6 patients (71 to 88 years) with cervical stump squamous cell carcinoma have been treated by external beam radiotherapy (IMRT, 45Gy in 25 fractions (5 patients) and 50,4Gy in 28 fractions (1 patient)) with concomitant chemotherapy in 2 patients, followed by Image Guided adaptive brachytherapy with Pulsed Dose Rate (5 patients) or High Dose Rate (1 patient). We used the Utrecht Interstitial BT applicator (ELEKTA), with the implant of bilateral (3 patients) or unilateral (3 patients) external interstitial needles and the insertion of the four interstitial internal needles within the residual cervix (3 patients). Dosimetry was based on the GEC-ESTRO recommendations. Results The median HR-CTV volume was 15.15cc (12-35cc). The median dose delivered to 90% (D90) of the High-Risk and Intermediate Risk CTV was 81.2 (78.2- 89.8) and 68,95 (64.3-72.3) GyEQD2 respectively. With a 26,5 months median follow- up (10-92 months), we did not observe any local or distant recurrence. No grade 2 or more acute or late toxicities were reported. Conclusion Cervix brachytherapy with a standard applicator using interstitial needle is safe and effective in cervical stump cancer patients.