This research considers potential dose increase in target due to cisplatin (Pt) concentration and radiation type. Cisplatin concentrations from 0.003 to 120 mM were used. Monte-Carlo simulation of Linear accelerator (Elekta Synergy) and X-ray tube (Xstrahl300) was carried out using Geant4 and PClab. As the first step of this research, we performed simulation of energy spectrum from radiotherapy units (spectrum model). The next step was the modeling of linear accelerator head and X-ray tube, and the distribution of dose in the water phantom (PDD model). At the second stage, dose changes were investigated in the presence of cisplatin in the target (CIS model). The simulation results showed that the dose escalation can be caused by photon-capture therapy (PCT). There is a dose enhancement in the volume where cisplatin is accumulated. Then higher is concentration, then higher is the effect. However, the photon energy increase from 60 to 250 kV and increase of depth of target reduces the effect of PCT due the decrease of the photoelectric effect cross-section. Should be noticed, that the orthovoltage X-rays energy, listed in the table with results shows higher dose enhancement, than the megavoltage photon beam generated from linear acceleration sources. In addition, that the dose enhancement factors (DEF) are higher in linac without flattening filter, than in linac with flattening filter.

OBJECTIVE The authors sought to evaluate clinical outcome in patients with large, high-risk brain metastases (BMs) treated with different dose strategies by use of two-fraction dose-staged Gamma Knife radiosurgery (GKRS). METHODS A retrospective analysis was performed with data from 142 patients from two centers who had been treated with two-fraction dose-staged GKRS between June 2015 and January 2020. Depending on the changes in marginal dose between the first (GKRS1) and second (GKRS2) GKRS treatments, the study population was divided into three treatment groups: dose escalation, dose maintenance, and dose de-escalation. RESULTS The 142 study patients underwent two-fraction dose-staged GKRS treatments for 166 large, high-risk BMs. The median tumor volume of 7.4 cm3 decreased significantly from GKRS1 to GKRS2 (4.4 cm3; p < 0.001), and to the last follow-up (1.8 cm3; p < 0.001). These significant differences in BM volume reduction were achieved in all three treatment groups. However, differences according to the primary tumor histology were apparent: while dose maintenance seemed to be the most effective treatment strategy for BMs from lung cancer or melanoma, dose escalation was the most beneficial treatment option for BMs from breast, gastrointestinal, or genitourinary cancer. Of note, the vast majority of patients who underwent dose-staged BM treatment did not show any significant postradiosurgical complications. CONCLUSIONS In patients with large, high-risk BMs, dose-staged GKRS treatment represents an effective local treatment method with acceptable complication risks. Different dose-strategy options are available that may be chosen according to the primary tumor histology and treatment volume but may also be tailored to the findings at GKRS2.

The paper presents the experience of use a new surgical technique in the treatment of gastroesophageal reflux disease, which consists of laparoscopic fixing of the His angle by using new biological material - xenopericard made in the form of tape. The access, the sequence and progress of surgical intervention, the advantages of plastic material – calfspericard - are described in details. The implant has a high mechanical strength, a smooth sliding surface, antigenic resistance, bio-resistance while contact with the surrounding tissues and high bio-integration with esophagus, that allowing to prevent possible the prosthesis associated complications, and to obtain good functional results. The anti-reflux surgery is performed using endoscopic original universal access, allowing to performing simultaneous operations. Method is technically simple, non-invasive, absence of stage of mobilization of the stomach and excludes damage to the branches of the vagus nerve, thus prevent the occurrence of postoperative evacuation disorders. Result of the operation using the new method is the restoration of normal topographic anatomical relationships between structures of the esophagogastric junction and recreation of a reliable anti-reflux mechanism. The clinical observation and generalized results of treatment of 36 patients demonstrate the effectiveness of the proposed method for the surgical treatment of gastroesophageal reflux disease.

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Radiation therapy in the presence of heavy elements nuclei (Z > 53) is widely developed these days. The presence of such nuclei in cancer cells results in the local increase of energy release from primary photon beam thus increasing relative biological efficiency. In this paper we present the preliminary results of the cell survival study while irradiating cells by X-Ray photon beam in the presence of cisplatin (Pt, Z = 78). The preliminary results show the decrease of the cell survival in the presence of both radiation and cisplatin.