Preoperative Proton Irradiation for High-grade Brain Gliomas. (PPrestige)

High grade gliomas (HGG), especially glioblastomas, are among those disease, for which oncological science doesn't propose any improvements for several decades, since temozolomide became a part of therapy. Preoperative irradiation is a standard of care for various malignant diseases. Historically, for intracranial targets preoperative RT is a taboo. Besides, recent data from preoperative RT of brain metastasis showed promising results and good toxicity profile. We would like to investigate the hypotheses of preoprative proton short-course irradiation can be tolerable and potentially improve outcomes in HGG patients.

High-grade gliomas (astrocytomas CNS WHO grade 3-4, glioblastomas, etc) are the most common primary brain tumors, with an extremely poor survival prognosis and a median overall survival of approximately 15-18 months [1, 2]. Recent advances in drug therapy have, unfortunately, not made a substantial contribution to improving treatment outcomes. Therefore, novel approaches to enhance treatment efficacy are more relevant than ever, and over the past decades, the use of radiotherapy has indeed improved survival in these patients. The standard treatment protocol currently includes maximal safe surgical resection followed by chemoradiotherapy, which is initiated 4-6 weeks after surgery [3]. However, microscopic foci of tumor cells in the postoperative period may proliferate and become manifest even before the start of radiotherapy. A recent meta-analysis showed that 40-50 % of patients with high-grade gliomas experience disease progression already during the interval between surgery and adjuvant treatment [4]. Since complete tumor resection is virtually unattainable, intensification of preoperative treatment may represent an effective option, as it targets the disease at an earlier and potentially more vulnerable stage [5].

There is considerable interest in early treatment strategies for high-grade gliomas that target the pre-, intra-, or early postoperative tumor microenvironment [5]. Preoperative radiotherapy is of particular interest, given the encouraging results observed in many other tumor types; however, it has never been applied to high-grade gliomas before [6, 7, 8, 9]. The preoperative period offers more favorable therapeutic characteristics compared with the postoperative tumor microenvironment, including less tumor hypoxia and molecular heterogeneity, which may consequently enhance the effectiveness of irradiation at this stage [5]. Data from dose-escalation safety studies suggest that a radiation dose additional to the standard postoperative regimen (60 Gy/30 fractions) can be delivered safely, but it remains unclear whether dose escalation can improve patient outcomes [10]. Currently, there are only a limited number of studies on preoperative radiotherapy for high-grade gliomas at various stages of preclinical and clinical investigation [6, 11, 12].

Proton therapy is currently the most sparing modality of radiotherapy, allowing, through its unique dose-distribution characteristics, a significant reduction in exposure to normal tissues-a particularly important consideration when irradiating the brain [13]. The use of proton therapy has been widely established both in primary tumors of the nervous system, including extreme dose escalation in glioblastomas, and in re-irradiation settings [14, 15]. Accumulated clinical experience suggests that the application of protons in the pre- and postoperative setting in patients with high-grade gliomas of the brain may minimize the risks of radiation complications and open up new therapeutic opportunities for this disease.