ESTRO 2024 - Abstract Book

S71 ESTRO 2024 multi-criteria optimization (MCO) approaches including DVH parameters, with recent examples from the literature. MCO approaches provide a number of treatment plans belonging to the Pareto front, that is, no single criterion can be improved without worsening another. We will further discuss possibilities and challenges in MCO approaches, for example regarding visualization and navigation of the Pareto front. In the last part, there will be an outlook of the next steps toward automated treatment planning and the remaining challenges. The role and potential of AI and its combination with MCO will also be discussed. Invited Speaker

3438

Navigating the opportunities and challenges of novel SRS/SRT methods: A medical physicist's perspective

Per Munck af Rosenschold

Lund University, Radiation Physics, Lund, Sweden

Abstract:

In this contribution we wish to give an overview of the advantages, limitations, and some possibilities of future advances in the realm of stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT). The pivotal role of optimization and planning tools in enhancing radiotherapy quality will be discussed. Further, we explore the technical constraints that current standards, specifically addressing the precision achievable in targeting small intra-cranial lesions and the consideration of treating multiple metastases disease in treatment planning. There are currently several treatment systems at our disposal in the radiotherapy field. These systems offer different sets of benefits, including by means of precision of targeting tissues. There are a few aspects needed to be considered in the case of SRS, including geometrical precision, delivery speed, degrees of freedom regarding irradiation directions, modulation potential, surface and image-guided monitoring. Personalized treatment plans tailored to individual patient needs by reduction of damage to surrounding healthy cells can be met by intensity modulation. The methods and indices suggested for comparison of plans will be reviewed (Paddick, RTOG, etc). Currently, we have a series of commercial clinical systems well-suited to offer high-quality SRS. The ability to accurately target and treat small tumors or metastatic sites is crucial for the success of SRS and SRT. For the treatment of brain metastases, the objective is to achieve high level of local control while preserving neurological function, and subsequently, reducing mass-effect. Recent meta-analysis of intra-cranial brain metastases data demonstrate 1-year local control rates of around 85-95% with single-fraction SRS to small tumors, while significantly lower for larger tumors (Redmond et al, 2021). Importantly, the actuarial rates of radiation-induced risk of brain necrosis demonstrated a strong association with irradiated volume. The risk of systematic brain necrosis has been reported to be typically around 10-20% (Milano et al, 2021). Clearly, the optimization of an SRS protocol involves striking the best possible balance between a tumoricidal dose while minimizing the risk of symptomatic brain necrosis. Also, the dosimetry of the optical nerves and the brainstem, must be considered. In relation to this topic, Planning Target Volume (PTV) calculation will be reviewed in terms of evidence and represent another critical aspect of treatment planning. Factors such as tumor size, location, and the proximity of sensitive structures may influence the choice of PTV margins, with the overarching goal of maximizing treatment efficacy while minimizing adverse effects.