ESTRO 2025 - Abstract Book

S48

Invited Speaker

ESTRO 2025

metastatic cancers by enhancing the immunomodulatory effects of radiation therapy and improving the efficacy of immunotherapies through sustained, local delivery.

Although combining brachytherapy with immunotherapy holds promise, further research is required to optimise treatment regimens, including dose, fractionation, timing, and sequencing. Prospective clinical trials are critical to better understanding the interaction between these modalities. References: 1. Patel RB, Baniel CC, Sriramaneni RN, Bradley K et al. Combining brachytherapy and immunotherapy to achieve in situ tumor vaccination: A review of cooperative mechanisms and clinical opportunities. Brachytherapy. 2019 Mar;18(2):240. 2. Rehman LU, Nisar MH, Fatima W, Sarfraz A et al. Immunotherapy for Prostate Cancer: A Current Systematic Review and Patient Centric Perspectives. J Clin Med. 2023 Feb 11;12(4):1446. 3. Maisch P, Koll F, Bolenz C, Chun FKH et al. Combination of radiation and immunotherapy in the treatment of genitourinary malignancies: A systematic review and meta-analysis. Urol Oncol Semin Orig Investig. 2023 May;41(5):219–32. 4. Fleischmann M, Glatzer M, Rödel C, Tselis N. Radioimmunotherapy: future prospects from the perspective of brachytherapy. J Contemp Brachytherapy. 2021;13(4):458–67. 5. Saidian A, Dolendo I, Sharabi A, Stewart TF et al. The Current and Future Promises of Combination Radiation and Immunotherapy for Genitourinary Cancers. Cancers. 2022 Dec 25;15(1):127. 6. Kelly G, Milligan JJ, Mastria EM, Kim S et al. Intratumoral delivery of brachytherapy and immunotherapy by a thermally triggered polypeptide depot. J Controlled Release. 2022 Mar;343:267–76. Speaker Abstracts The role of interventional radiotherapy (brachytherapy) in the immunotherapy era: Focus on gynaecological cancers Ina Jürgenliemk-Schulz Radiation Oncology, University Medical Center Utrecht, Utrecht, Netherlands Abstract: Radioimmunotherapy originates from the idea to use radionuclides linked to monoclonal anti-tumour antibodies to treat cancer. For gynaecological tumours, this concept found clinical importance and implementation especially for ovarian cancer and abdominal carcinomatosis. There is no major activity or breakthrough in this field for gynaecological cancers of other origin. However, radioimmunotherapy, also includes combinations of radiotherapy and immunotherapeutic agents with rapidly growing interest in the last two decades. This includes gynaecological cancers and especially cervical cancer. There is growing interest for the use of monoclonal antibodies against vascular epithelial growth factor (VEGF) or immune check points (PD-1/PDL-1), which can activate intra-cellular mechanisms to induce cancer cell death. Several of these antibodies are currently being investigated in pre-clinical and clinical studies, including the search for biomarkers for their use and clinical trials with palliative or curative intention. For anti-VEGF antibody bevacizumab effectiveness has been demonstrated in recurrent or stage IVb disease, however, with an increased risk of major morbidities in case radiotherapy has been applied. Currently, immune check point inhibitors in combination with (chemo) radiotherapy and brachytherapy are being assessed in clinical trials, especially for advanced cervical cancer. Among others, anti-PD-1 antibodies pembrolizumab, nivolumab, cemiplimab, and anti-PDL-1 antibodies azetolizumab, avelumab, durvalumab have been with mixed clinical results. In CALLA (NCT03051906), no clinical gain could be demonstrated using durvalumab in combination with radiotherapy for advanced cervical cancer. Keynote A-18 (NCT04221945) combining pembrolizumab with chemoradiotherapy and brachytherapy was recently published, demonstrating improved survival in the study arm, however not that differing from survival results as obtained in recent chemoradiotherapy trials including 4726