Dynamics of sheath-connected plasma filaments in magnetic field with arbitrary geometry

We present the results of analysis of sheath-connected blob dynamics in magnetic field with arbitrary geometry. For the case of magnetic configurations with small curvature of the field lines it is demonstrated that motion of a plasma filament can be described by a single time-independent effective potential. Dynamics of blobs in magnetic fields with non-zero curvature of the field lines is also analyzed and we show that depending on filament dimensions and geometry of the magnetic field blobs can demonstrate different propagation patterns. The qualitative results of the presented analysis are supplied with results of simulations of filament dynamics in sheared and non-sheared tokamak-like magnetic configurations. Keywords: Plasma filaments, Blob dynamics, Magnetic field with arbitrary geometry, Magnetic shea

Energy balance in plasma detachment

Divertor plasma detachment is analyzed from the viewpoint of energy and particle balance in the edge plasma. It is shown that volumetric recombination and impurity radiation losses are responsible for the transition to the detached plasma regime, whereas “momentum removal” plays although important, but auxiliary role providing conditions necessary for the first two to become efficient. A criterion of the local (on an isolated flux tube) detachment onset is studied for both pure and impurity-seeded plasmas. Keywords: Divertor, Detachment, Impurity, Recombinatio

Role of molecular effects in divertor plasma recombination

Molecule-Activated Recombination (MAR) effect is re-considered in view of divertor plasma conditions. A strong isotopic effect is demonstrated. In deuterium plasmas, the reaction chain through D2+ formation, usually considered dominant and included in 2D edge plasma models, is negligible. However, in this case the other branch, through D−, usually neglected in modelling, becomes relatively strong. The overall share of MAR in divertor plasma recycling stays within 20%. The operational parameters of the divertor plasmas, such as the peak power loading on the divertor targets or the pressure limit for partial detachment of the divertor plasma, are insensitive to the presence of MAR, although the latter may be important for correct interpretation of the divertor diagnostics. Keywords: Tokamak, Divertor, Recombination, MA

Stability of divertor detachment

The 2D simulations of edge plasma transport show that unlike some earlier publications, the impurity radiation loss per se does not cause the bifurcation-like transition to detached divertor regime. However, for the case where anomalous plasma transport is increasing with advancement to detachment, like it was recently observed experimentally, the transition to detachment exhibit the bifurcation-like character. Some other plausible reasons for similar bifurcation-like evolution to detachment are discussed. It is demonstrated that the current convective instability can be triggered in detached inner divertor plasma for the condition when outer divertor is still attached. This can explain the fluctuations of radiation loss observed recently experimentally for similar conditions. The self-sustained oscillations observed recently in numerical simulations and related to the interplay of the thermal force effects in impurity transport and impurity radiation loss are further investigated. It is shown that for some conditions these oscillations are ubiquitous, since no stable solutions possible. Keywords: Divertor detachment, Stability, Bifurcation, Impurity, Anomalous transport, Recyclin

Neoadjuvant chemohormonal therapy and radical prostatectomy in a patient with lymphogenic metastatic prostate cancer

Prostate cancer (PC) is now one of the most common malignancies among men. Radical prostatectomy is the most commonly used therapy option for patients with localized PC. The appropriateness of surgical treatment for locally advanced and lymphogenic metastatic PC remains controversial, as the probability of non-radical intervention increases significantly and the risk for disease progression becomes higher. At the same time, interest in surgical treatment in patients with PC at high risk of progression, including those with lymphogenic metastases has recently increased greatly. There are more and more studies demonstrating improved survival rates in patients with high-risk PC, including those with distant metastases, who have undergone radical prostatectomy and lymphadenectomy compared with a cohort of patients who have received only drug therapy In addition to the studies evaluating the efficiency of neoadjuvant therapy before surgery in patients with localized or locally advanced high-risk PC, there are also investigations considering this option in PC patients with lymphogenic metastases. The paper gives the results of a clinical observation that shows the high efficiency of a multimodal approach with neoadjuvant chemohormonal therapy, followed by surgical treatment in a patient with lymphogenic metastatic PC

Neoadjuvant and adjuvant chemohormonal therapy in patients with high-risk and very high-risk prostate cancer: Our experience

Background. The approach to the management of prostate cancer with lymph node metastases has recently moved towards aggressive multi-modal treatment with the use of the most rational combinations that are currently available. Objective: to assess the efficacy and tolerability of chemohormonal therapy (CHT) in patients with high-risk and very high-risk prostate cancer. Materials and methods. An open prospective clinical trial evaluating the efficacy and tolerability of neoadjuvant and adjuvant CHT in patients with high-risk and very high-risk prostate cancer was initiated in 2016 at the P.A. Herzen Moscow Oncology Research Institute. Patient recruitment is still ongoing. A total of 64 patients with high-risk and very high-risk prostate cancer (сT3N0-T3N+М0, prostate specific antigen (PSA) ≥20 ng/mL, and Gleason score of 8-10) were recruited since July 2016. All patients were examined prior to treatment initiation and after 3 and 6 courses of therapy. The examination included pelvic magnetic resonance imaging, ultrasound imaging of the abdominal cavity and retroperitoneal space, transrectal ultrasound imaging, and chest radiography or computed tomography. Serum PSA level was evaluated before each course of therapy. Bone scintigraphy was performed before treatment and after its completion. Study participants were divided into two groups. Group A included patients that initially underwent surgical treatment and then 6 courses of CHT no later than 6 weeks after surgery: docetaxel 75 mg/m2 given intravenously on day 1 of a 21-day cycle and oral prednisolone 10 mg/day. Patients also received hormonal therapy with luteinizing hormone-releasing hormone analogue (aLHRH) given in depot injections every 28 days. Group B included patients that initially received 6 courses of CHT: docetaxel 75 mg/m2 given intravenously on day 1 of a 21-day cycle and oral prednisolone 10 mg/day. After that, patients underwent radical prostatectomy with pelvic lymphadenectomy no later than 4 weeks after the completion of chemotherapy. Patients also received hormonal therapy with aLHRH given in depot injections every 28 days. The total treatment duration was 6 months. Results. The group of adjuvant CHT included 24 patients with high-risk prostate cancer (T3b-4N+М0 with at least 5 regional lymph node metastases detected by morphological examination of surgical specimens). All patients had Gleason score 8-10 tumors. Mean age of patients was 63.0 ± 7.7 years (range: 46-72 years). In total, all patients received 142 courses of CHT. By the time of publishing this article, 23 (96 %) of patients completed their treatment. The group of neoadjuvant CHT included 40 patients with very high-risk prostate cancer (T3b-4N+М0 with metastases to pelvic and retroperitoneal lymph nodes detected by instrumental examination). All patients had Gleason score 8-10 tumors. Mean age of patients was 61.0 ± 6.4 years (range: 43-69 years). In total, all patients received 236 courses of CHT. By the time of publishing this article, 36 (90 %) of patients completed their treatment. Thirty-five patients (87 %) underwent radical prostatectomy with extensive pelvic and paraaortic lymphadenectomy. Routine pathological examination demonstrated that all patients had signs of tumor destruction. Thirty-three participants (94 %) had grade II therapeutic pathomorphosis, whereas 2 patients (6 %) had grade III therapeutic pathomorphosis. Median PSA relapse-free survival (PSA-RFS) rate in the neoadjuvant CHT group was 10 months. Serum PSA of 0.1 ng/mL 1 month postop-eratively correlated with longer RFS (р = 0.04). Biochemical relapse (PSA level >0.2 ng/mL) was observed in 6 patients (15 %) from this group. Later these patients received hormonal therapy with aLHRH. Median PSA-RFS in the adjuvant CHT group was 11 months. The main adverse events in the two groups were hematological toxicity, observed in 24 patients (34.29 %), and gastrointestinal toxicity, observed in 9 patients (12.86 %) (diarrhea (n = 6) and stomatitis (n = 3)). Only grade I-II toxicity was registered so far. Two patients (3.1 %) had febrile neutropenia, which required cytostatic dose reduction by 20 %. Relatively good tolerability and acceptable quality of life allowed the vast majority of patients to be treated on an outpatient basis. Conclusion. So far, we can make only a preliminary conclusion that adjuvant and neoadjuvant CHT is a promising treatment strategy for high-risk and very high-risk prostate cancer. © ABC-press Publishing House. All rights reserved

Neoadjuvant chemohormonal therapy and radical prostatectomy in a patient with lymphogenic metastatic prostate cancer

Prostate cancer (PC) is now one of the most common malignancies among men. Radical prostatectomy is the most commonly used therapy option for patients with localized PC. The appropriateness of surgical treatment for locally advanced and lymphogenic metastatic PC remains controversial, as the probability of non-radical intervention increases significantly and the risk for disease progression becomes higher. At the same time, interest in surgical treatment in patients with PC at high risk of progression, including those with lymphogenic metastases has recently increased greatly. There are more and more studies demonstrating improved survival rates in patients with high-risk PC, including those with distant metastases, who have undergone radical prostatectomy and lymphadenectomy compared with a cohort of patients who have received only drug therapy In addition to the studies evaluating the efficiency of neoadjuvant therapy before surgery in patients with localized or locally advanced high-risk PC, there are also investigations considering this option in PC patients with lymphogenic metastases. The paper gives the results of a clinical observation that shows the high efficiency of a multimodal approach with neoadjuvant chemohormonal therapy, followed by surgical treatment in a patient with lymphogenic metastatic PC