Towards bridging non-ionizing, ultra intense, laser radiation and ionizing radiation in cancer therapy

In oncology, cancer radiotherapy is a well-established therapeutic technique for more than 100 years and, worldwide, about two-thirds of all cancer patients will undergo conventional X-rays or gamma-rays therapy, as monotherapy or as part of their treatment, to destroy tumor cells by damaging their DNA. As the high energy electromagnetic waves based radiotherapy is not equally effective in all types and location of cancerous tumors, radiotherapy using accelerator based hadron beams is a well-established alternative, especially for deep-placed tumors, as a result of the well-known Bragg peak phenomenon. External proton beam radiation therapy is most commonly used in the treatment of pediatric, central nervous system and intraocular cancers. To overcome the major obstacle of the very expensive proton production facilities (through accelerators) in building of proton cancer treatment medical centers, the use of high-power lasers for particle radiation production was proposed. The recent development of lasers with ultrashort pulses (e.g. with pulse lengths around 30 fs) resulted in particle acceleration from the rear side of a laser-irradiated thin foil, based on their unique properties and laser-matter interaction mechanisms. In this review work, we aim to present the progress toward laser-driven radiotherapy, as well as to discuss if and how the radiobiological effectiveness of particle radiation generated by lasers differs from that provided by other conventional techniques. We will discuss the expectations and limitations in anti-cancer laser-driven proton therapy, reported in literature over the last decade. In the framework of the national project HELLAS-CH, we will present some of the preliminary efforts on the combined photodynamic and ionizing radiation action, with ultra-fast laser pulses, on tissue simulators and biological samples.