Treatment Planning in Intraoperative Radiation Therapy (IORT): Where Should We Go?

Abstract

As opposed to external beam radiation therapy (EBRT), treatment planning systems (TPS) dedicated to intraoperative radiation therapy (IORT) were not subject to radical modifications in the last two decades. However, new treatment regimens such as ultrahigh dose rates and combination with multiple treatment modalities, as well as the prospected availability of dedicated in-room imaging, call for important new features in the next generation of treatment planning systems in IORT. Dosimetric accuracy should be guaranteed by means of advanced dose calculation algorithms, capable of modelling complex scattering phenomena and accounting for the non-tissue equivalent materials used to shape and compensate electron beams. Kilovoltage X-ray based IORT also presents special needs, including the correct description of extremely steep dose gradients and the accurate simulation of applicators. TPSs dedicated to IORT should also allow real-time imaging to be used for treatment adaptation at the time of irradiation. Other features implemented in TPSs should include deformable registration and capability of radiobiological planning, especially if unconventional irradiation schemes are used. Finally, patient safety requires that the multiple features be integrated in a comprehensive system in order to facilitate control of the whole process.

In vivo dosimetry in cancer patients undergoing intraoperative radiation therapy

“…On-line imaging in combination with treatment planning could reduce the uncertainties in target assessment and applicator placement for IORT. In contrast to EBRT, treatment planning systems (TPS) for IORT did not see substantial changes during the last two decades (Cavedon and Mazzarotto 2022). Moreover, in-room imaging systems were not used routinely with IORT until now (Hensley 2017).…”

Full-Dose Intraoperative Electron Radiotherapy for Early Breast Cancer: Evidence from a Single Center’s Experience

“…In the last two decades, the introduction of dedicated mobile accelerators increased the popularity of intraoperative electron RT (IOERT), and the criteria for patient selection were reviewed in 2020 by the European Society for Radiotherapy and Oncology (ESTRO) [ 17 ]. Moreover, the possibility of combination of different IORT treatment modalities as the use of ultrahigh dose rates in a dedicated in-room imaging system can direct to a better optimization of the treatment and consequently to achieve better clinical outcomes [ 18 ]. More recently, full-dose IOERT was shown to have non-inferiority compared with whole-breast (WB)RT in terms of cosmesis [ 19 ], and excellent LC was reported in an Italian multicenter analysis for anticipated IOERT boost for early-stage BC [ 20 ].…”