A modeling investigation was performed to choose moderator material and size for creating optimal epithermal neutron beams for BNCT based on a proton accelerator and the 7 Li(p,n) 7 Be reaction as a neutrons source. An optimal configuration is suggested for the beam shaping assembly made from polytetrafluoroethylene and magnesium fluorine. Results of calculation were experimentally tested and are in good agreement with measurements.

Proton therapy (PT) due to dosimetric characteristics (Bragg peak formation, sharp dose slowdown) is currently one of the most hightech techniques of radiation therapy exceeding the standards of photon methods.In recent decades, PT has traditionally been used, primarily, for head and neck cancers (HNC) including skull base tumors. Regardless of the fact that recently PT application area has significantly expanded, HNC still remain a leading indication for proton radiation since PT's physic-dosimetric and radiobiological advantages enable to achieve the best treatment results in these tumors.The present review is devoted to PT usage in HNC treatment in the world and Russian medicine, the prospects for further technique development, the assessment of PT's radiobiological features, a physical and dosimetric comparison of protons photons distribution. The paper shows PT's capabilities in the treatment of skull base tumors, HNC (nasal cavity, paranasal sinuses, nasopharynx, oropharynx, and laryngopharynx, etc.), eye tumors, sialomas. The authors analyze the studies on repeated radiation and provide recent experimental data on favorable profile of proton radiation compared to the conventional radiation therapy.The review enables to conclude that currently PT is a dynamic radiation technique opening up new opportunities for improving therapy of oncology patients, especially those with HNC.

background: This study presents a retrospective analysis (efficacy and toxicity) of outcomes in patients with unresectable recurrence of previously irradiated head and neck (h&N) cancers treated with proton therapy. Locoregional recurrence is the main pattern of failure in the treatment of h&N cancers. proton re-irradiation in patients with relapse after prior radiotherapy might be valid as promising as a challenging treatment option. Materials and methods:From November 2015 to January 2020, 30 patients with in-field recurrence of head and neck cancer, who were not suitable for surgery due to medical contraindications, tumor localization, or extent, received re-irradiation with intensity-modulated proton therapy (IMpT). sites of retreatment included the aerodigestive tract (60%) and the base of skull (40%). The median total dose of prior radiotherapy was 55.0 Gy. The median time to the second course was 38 months. The median re-irradiated tumor volume was 158.1 cm 3 . patients were treated with 2.0, 2.4, and 3.0 GyrBe per fraction, with a median equivalent dose (eQD 2 ) of 57.6 Gy (a/b = 10). radiation-induced toxicity was recorded according to the rTOG/eOrTc criteria. results:The 1-and 2-year local control (Lc), progression-free survival (pFs), and overall survival (Os) were 52.6/21.0, 21.9/10.9, and 73.4/8.4%, respectively, with a median follow-up time of 21 months. The median overall survival was 16 months. acute grade 3 toxicity was observed in one patient (3.3%). There were five late severe side effects (16.6%), with one death associated with re-irradiation. conclusion: re-irradiation with a proton beam can be considered a safe and efficient treatment even for a group of patients with unresectable recurrent h&N cancers.

Treatment of breast cancer (BC) is a complex multidisciplinary problem. Often, radiation therapy is an obligatory component of treatment of breast cancer patients. Numerous large randomized trials have proved the efficacy of adjuvant radiotherapy in both the standard fractionation regimen in a single focal dose of 2 Gy to a total focal dose of 50 Gy for 25 fractions and in modes of hypofractionation using radiation exposure at a larger daily dose with a reduction in the total treatment time. The presented review summarizes the data of the largest studies on the modes of hypofractionation of postoperative radiotherapy for breast cancer. Most of the studies comparing the standard mode of fractionation of postoperative radiotherapy with the modes of hypofractionation showed comparable results for the main oncological parameters with similar tolerability, frequency of complications and good cosmetic results. It also shows the economic feasibility of applying accelerated regimes in everyday practice. Despite the fact that radiotherapy in the mode of hypofractionation has already become the standard of treatment and is recommended for use by the largest European and American cancer associations, indications for its conduct, the criteria for selection in the studies and the range of recommended single focal doses differ. The obtained results do not give an opportunity to confidently judge the advantage of one or another regime. It is necessary to determine the factors of a favorable and unfavorable prognosis, to clarify the indications for the use of various radiotherapy techniques. Therefore, questions about the optimal mode of hypo-fractionation of adjuvant radiotherapy, the timing of its initiation and the criteria for selecting patients for this type of therapy as part of the comprehensive treatment of breast cancer have not yet been fully resolved. Also open is the choice of optimal single and total doses of radiation, its combination with drug therapy.

Aim This study presents an analysis (efficacy and toxicity) of outcomes in patients with skull-base chordomas or chondrosarcomas treated with a fixed horizontal pencil proton beam. Background Chordomas (CAs) and chondrosarcomas (CSAs) are rare tumours that are usually located near the base of the skull and very close to the brain's most critical structures. Proton therapy (PT) is often considered the best radiation treatment for these diseases, but it is still a limited resource. Active scanning PT delivered via a fixed pencil beamline might be a promising option. Methods This is a single-centre experience describing the results of proton therapy for 31 patients with CA (n = 23) or CSA (n = 8) located near the base of the skull. Proton therapy was utilized by a fixed pencil beamline with a chair to position the patient between May 2016 and November 2020. Ten patients underwent resection (32.2%), 15 patients (48.4%) underwent R2 resection, and 6 patients had unresectable tumours (19.4%). In 4 cases, the tumours had been previously irradiated. The median PT dose was 70 GyRBE (relative biological efficacy, 1.1) [range, 60 to 74] with 2.0 GyRBE per fraction. The mean GTV volume was 25.6 cm3 [range, 4.2–115.6]. Patient demographics, pathology, treatment parameters, and toxicity were collected and analysed. Radiation-induced reactions were assessed according to the Common Terminology Criteria for Adverse Events (CTCAE) v 4.0. Results The median follow-up time was 21 months [range, 4 to 52]. The median overall survival (OS) was 40 months. The 1- and 2-year OS was 100%, and the 3-year OS was 66.3%. Four patients died due to non-cancer-related reasons, 1 patient died due to tumour progression, and 1 patient died due to treatment-related injuries. The 1-year local control (LC) rate was 100%, the 2-year LC rate was 93.7%, and the 3-year LC rate was 85.3%. Two patients with CSA exhibited progression in the neck lymph nodes and lungs. All patients tolerated PT well without any treatment interruptions. We observed 2 cases of ≥ grade 3 toxicity, with 1 case of grade 3 myelitis and 1 case of grade 5 brainstem injury. Conclusion Treatment with a fixed proton beam shows promising disease control and an acceptable toxicity rate, even the difficult-to-treat subpopulation of patients with skull-base chordomas or chondrosarcomas requiring dose escalation.