ESTRO 2025 - Abstract Book

S589

Clinical - Breast

ESTRO 2025

Results: The study closed early after 86 of the planned 120 patients were enrolled. 79 patients completed the study as planned: 40 in the HA cream group and 39 in the placebo group. Among patients undergoing hypofractionated RT, 41.7% in the HA group and 57.7% in the placebo group developed grade 1 dermatitis by the end of RT. No patients in the hypofractionated group developed >grade 2 dermatitis, whereas 10 patients under conventional fractionation did. The primary endpoint analysis showed no significant difference between the two groups (p=0.3477). Clinical RTOG scores and SRS measures of acute radiodermatitis followed similar patterns in both treatment groups. Time to onset of dermal toxicity (RTOG ≥ G1) was comparable between groups, with a shorter onset in the hypofractionation schedule. SRS values increased rapidly from week 1 of RT, continuing throughout, and decreased post-RT more notably in the conventional fractionation group. The ANCOVA model indicated no significant differences between treatment groups or RT schedules. Changes in SRS values and RTOG scores were similar across the study period. The patient-assessed level of discomfort at the irradiated area increased with time during RT and reached a maximum at the end-of-treatment visit. The discomfort was generally reported as mild in both treatment groups. No changes in patients’ quality of life were assessed by SF-36 at baseline and end-of-study periods. Conclusion: The extremely low incidence of grade 2 or higher radiodermatitis failed to show a significant benefit from the use of a topical hyaluronic acid-based cream. Additional studies are recommended to further evaluate the efficacy of HA based cream in preventing radiodermatitis. Digital Poster Tolerance of adjuvant radiotherapy after neoadjuvant chemo-immunotherapy for triple-negative breast cancer and impact of the immunotherapy regimen. Ludovic HERNANDEZ 1 , Tamasine KHADROUCHE 2 , Mathilde MORISSEAU 3 , Amélie LUSQUE 3 , Ciprian CHIRA 1 , Audrey KELLER 1 , Françoise IZAR 1 , Céline DALMASSO 1 , Mony UNG 4 , Eleonora DE MAIO 4 , Eva JOUVE 2 , Carole MASSABEAU 1 1 Radiotherapy, IUCT Oncopole, Toulouse, France. 2 Surgery, IUCT Oncopole, Toulouse, France. 3 Biostatistic, IUCT Oncopole, Toulouse, France. 4 Medical oncology, IUCT Oncopole, Toulouse, France Purpose/Objective: The KEYNOTE-552 trial established chemo-immunotherapy with neoadjuvant and adjuvant pembrolizumab as the standard of care for locally advanced triple-negative breast cancer (TNBC). However, detailed data on the safety of combining immunotherapy with other modalities are lacking, particularly adjuvant radiotherapy (RT). This raises further questions regarding the optimal therapeutic sequence. This study compared the acute tolerance (≤6 months) of RT in patients who did or did not receive pembrolizumab, and whether it was delivered concomitantly or sequentially with RT. Material/Methods: This single enter retrospective study included patients with non-metastatic TNBC, regardless of stage, who received adjuvant RT after neoadjuvant treatment. Neoadjuvant treatment consisted of either chemotherapy alone (RT alone group) or chemo-immunotherapy with pembrolizumab (RT+P group), followed by adjuvant RT. Pembrolizumab, when continued as adjuvant therapy, was administered either concomitantly or sequentially with RT. Radiation induced adverse events were assessed using the CTCAE.5 scale. Keywords: radiodermatitis, RT, hyaluronic acid cream 3629

Results: This study was conducted from October 2019 to April 2023, 110 patients were included: 54 in the RT alone group, 56