State of the art in Image Guided Radiotherapy

Pisa (Italy) – Recently, the advent of high-quality on-board imaging technology on radiotherapy equipment, coupled with tracking and gating technologies during treatment delivery, have fulfilled the goal of image-guided radiotherapy (IGRT). This has dramatically improved precision in tumour targeting and finally enabled reduction of safety margins around the target. The near complete removal of normal tissues from the volume exposed to high dose has rendered fractionation essentially dispensable, permitting the delivery of as high doses as required for tumour cure. This goal may be pursued at ultra-high doses per fraction (extreme hypo-fractionation) or even in a single dose exposure (Single-Dose IGRT). The latter two approaches have yielded an unprecedented quantum leap in local cure rates of human tumours, rendering obvious practical advantages in terms of patient convenience, machine throughput and overall treatment cost-effectiveness. The mechanism of tumor cure by ultra-high dose exposures is clearly distinct from the mechanism operating in classical fractionated radiotherapy and its radiobiology is gradually being unraveled. This difference may explain the dramatic advantage of the ultra-high dose approach in curing human cancer.

A growing body of clinical evidence indicates that the overall actuarial local cure for lesions receiving 24 Gy is approximately 90% in oligometastatic deposits, regardless of their anatomic location or histology of the primary tumour. Taken together, the published data provide evidence that SD-IGRT exceeds by far classical fractionated radiotherapy as a safe modality in rendering long-term local control, ablating human tumours without associated toxicities.

In this regard, SD-IGRT may outscore even surgery in many instances as a preferred approach to eradicate early stage disease such as in the case of borderline medically operable patients with stage I non-small cell lung cancer, where clinical evidence on the safety and efficacy of this approach is rapidly accruing in the literature. Current clinical challenges entail the design and implementation of trials incorporating IGRT in the management of a wider spectrum of primary tumours both as a sole treatment modality and in combination with surgery and/or systemic therapy.

Currently, The University of Pisa (UNIPI) is actively involved several projects dealing with advanced IGRT techniques. In collaboration with Memorial Sloan Kettering Cancer Center in New York, the University Hospital of Pisa (AOUP) is accruing patients with oligometastatic disease in a phase III randomized study comparing SD-IGRT vs. Hypofractionation. These studies are successfully carried out thanks to the availability of a state-of-the-art IGRT platform (TrueBeam STx) which is operated by the medical and technical staff of the University Hospital of Pisa (AOUP) within the framework of an institutional collaboration with Casa di Cura San Rossore where the device is installed.

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