S3028
Invited Speaker
ESTRO 2026
OMBC and how combined treatment shall be delivered. References: Major references: Harrow S, Palma DA, Olson R et al (2022). Int J Radiat Oncol Biol Phys 114(4):611–616. Chmura SJ, Winter KA, Woodward WA et al (2022). J Clin Oncol 40(16_suppl):1007–1007. https://doi. org/ 10. 1200/ JCO. 2022. 40. 16_ suppl. 1007. Reddy JP, Sherry AD, Fellman B et al (2024). Int J Radiat Oncol Biol Phys. 2025 Mar 15;121(4):885-893. Salvestrini V, Kim K, Caini S et al (2023) Radiother Oncol. 2023 Sep;186:109805. Meattini I, Becherini C, Caini S et al (2024). European Society for Radiotherapy and Oncology (ESTRO)- endorsed recommendations. Lancet Oncol. 2024 Feb;25(2):e73-e83. Review Visani L, Ratosa I, Bartsch R (2026). Breast. 2026 Feb;85:104691. 5405 Why prediction models fail in clinical translation: Methodological pitfalls, clinical barriers and lessons learned Lisanne V vanDijk Radiotherapy, University Medical Center Groningen, Groningen, Netherlands Prediction models have the potential to become a powerful tool for realising personalised radiotherapy. By providing patient-specific estimates of toxicity, tumour control, and survival, they can support treatment decisions that move beyond the current one-size-fits-all approach and better tailor treatment to the individual patient. By identifying the patients who are most likely to benefit from treatment intensification or de-escalation, advanced radiotherapy techniques such as proton therapy, or supportive interventions, prediction models may improve outcomes, reduce unnecessary toxicity, and support more effective allocation of healthcare resources. Despite the benefits of personalised radiotherapy, only a limited number of prediction models have entered clinical practice. In this talk, I will discuss the few prediction models that have been clinically deployed, together with what has hampered others. Model performance alone is often not the limiting factor for clinical implementation. The central theme of this talk is what is needed to realise the clinical potential of prediction models responsibly. Key principles include robust model development, a clear treatment application, and the trust, reliability, and explainability required for clinical use. Clinical translation often does not fail because of a single weakness, but because of a chain of methodological
The oligometastatic (OM) disease state, characterized by a limited number of metastases, represents an intermediate stage between localized and widespread cancer, with outcomes superior to those of patients with disseminated disease. Standard management of oligometastatic breast cancer (OMBC) primarily involves systemic therapy. Local treatment in metastatic breast cancer (MBC) is generally reserved for symptomatic lesions. Type of systemic therapy and prognosis differ between BC subgroups. The French ESME database reports different overall survival (OS) according to BC subgroup: 50.1 months (HER2 positive); 42.9 months (hormone receptor positive) and 14.5 months (triple negative) MBC. The prognosis of patients with OMBC is probably better although data specifically on this group is scares. New efficient compounds such as cdk4/6-, PIK3-, mTOR-, AKT-, PARP- and Immune Checkpoint Inhibitors, TKIs and Antibody-Drug- Conjugates (ADCs) have further improved survival times but have a different mechanism of action than traditional chemotherapy that may interfere with radiotherapy. If the addition of metastasis directed local treatment improves survival for OMBC patients has gained research interest. Stereotactic ablative body radiotherapy (SABR) enables the delivery of high-dose, precise radiation with strong therapeutic efficacy and minimal toxicity to surrounding tissues. Results from three randomized phase II trials (SABR-COMET, NCT01446744; NRG-BR002, NCT02364557 and EXTEND NCT03599765) have shown conflicting outcomes, underscoring the need for further randomized studies on OMBC. Toxicity from SABR is reported to be manageable but available data when combined with new anti-cancer treatments in general derives from smaller retrospective series. With this limitation the recommendations from ESTRO international multidisciplinary consensus on the integration of radiotherapy with new systemic treatments are as follows: CDK4/6 inhibitors can be delivered without dose reductions and without increasing the number of SABR fractions; PIK-AKT inhibitors, PARP inhibitors and Sacitumab-govitecan with insufficient data should only be given concomitant with SABR within the frame of a prospective trial; mTOR inhibitors sequential administration is recommended; HER2-blocking agents not ADCs: there is an increased risk of radionecrosis when T-DM1 is given in conjunction to SABR toward intra cranial metastases; T-DXd, limited data but a recently published international study indicates that the combination is feasible and well tolerated, without a significant increase in acute or late treatment-related toxicity, also when RT was delivered with ablative intent. Ongoing prospective trials will give more solid data both on the efficacy of SABR in
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