Is curative gastrectomy justified for gastric cancer with cytology positive as the only stage IV factor?

AIMS: The prognosis of patients with gastric cancer and stage IV factors is poor. However, several recent studies have identified that curative surgery followed by S-1 chemotherapy for cytology positive (CY1) only patients contributed to a better prognosis. This study was designed to compare the prognosis between curative and palliative gastrectomy followed by chemotherapy in CY1 only stage IV gastric cancer. METHODS: Between 2001 and 2016, 1507 patients underwent gastrectomy for gastric cancer. Of these, 51 consecutive patients with only CY1 factor who underwent gastrectomy followed by chemotherapy were enrolled in this study. RESULTS: (1) Twenty three (45%) patients underwent curative D2 or D2+ gastrectomy, and the remaining 28 (55%) patients underwent palliative gastrectomy, followed by S-1 based or another historical recommended chemotherapy postoperatively. (2) Compared with patients undergoing palliative gastrectomy, patients undergoing curative gastrectomy had a significantly better prognosis (P = 0.042; median survival time: curative vs. palliative, 22.6 months vs. 11.8 months) and a lower incidence of recurrences (P = 0.091). Two- and five-year overall survival rates of patients following curative gastrectomy were 48.2% and 18.2%, respectively. A multivariate analysis showed that venous invasion [P = 0.006; hazard ratio (HR), 3.70 (95% CI: 1.27-9.43)] and curative gastrectomy [P < 0.005; HR, 0.28 (95% CI: 0.12-0.87)] were independent prognostic factors. CONCLUSION: Curative gastrectomy followed by chemotherapy might be justified to improve the prognosis of patients with only CY1 Stage IV gastric cancer.

Short Ballistic Josephson Coupling in Planar Graphene Junctions with Inhomogeneous Carrier Doping.

We report on short ballistic (SB) Josephson coupling in junctions embedded in a planar heterostructure of graphene. Ballistic Josephson coupling is confirmed by the Fabry-Perot-type interference of the junction critical current I_{c}. The product of I_{c} and the normal-state junction resistance R_{N}, normalized by the zero-temperature gap energy Δ_{0} of the superconducting electrodes, turns out to be exceptionally large close to 2, an indication of strong Josephson coupling in the SB junction limit. However, I_{c} shows a temperature dependence that is inconsistent with the conventional short-junction-like behavior based on the standard Kulik-Omel'yanchuk prediction. We argue that this feature stems from the effects of inhomogeneous carrier doping in graphene near the superconducting contacts, although the junction is in fact in the short-junction limit.

Self-expandable Metallic Stents Contribute to Reducing Perioperative Complications in Colorectal Cancer Patients with Acute Obstruction.

BACKGROUND/AIM: The self-expandable metallic stent (SEMS) is an excellent non-invasive tool for emergent bowel obstruction. This study was designed to evaluate the clinical usefulness of the SEMS for avoiding perioperative complications. PATIENTS AND METHODS: We analyzed a total of 47 consecutive patients who had a bowel obstruction due to colorectal cancer at initial diagnosis between 2012 and 2017 from hospital records. RESULTS: Perioperative complications occurred in 30% (14/47) of patients. Univariate and multivariate logistic regression analyses identified an age of more than 75 years [p=0.037, OR=6.84 (95% CI=1.11-41.6)] and the absence of an SEMS treatment [p=0.028, OR=18.5 (95% CI=1.36-250.0)] as independent risk factors for perioperative complications. Pneumonia (12.7% (6/47)) was the most common complication. There were no pneumonia patients (0% (0/15)) who were treated with the SEMS. In contrast to patients with the non-SEMS treatment, 18.7% (6/32) of all patients and 35.7% (5/14) of elderly patients had pneumonia. CONCLUSION: The SEMS is a safe and effective treatment for avoiding perioperative complications, particularly pneumonia, and may be a crucial strategy in elderly patients with acute obstruction due to colorectal cancer.

Engineering Dirac electrons emergent on the surface of a topological insulator.

The concept of the topological insulator (TI) has introduced a new point of view to condensed-matter physics, relating a priori unrelated subfields such as quantum (spin, anomalous) Hall effects, spin-orbit coupled materials, some classes of nodal superconductors, superfluid 3He, etc. From a technological point of view, TIs are expected to serve as platforms for realizing dissipationless transport in a non-superconducting context. The TI exhibits a gapless surface state with a characteristic conic dispersion (a surface Dirac cone). Here, we review peculiar finite-size effects applicable to such surface states in TI nanostructures. We highlight the specific electronic properties of TI nanowires and nanoparticles, and in this context we contrast the cases of weak and strong TIs. We study the robustness of the surface and the bulk of TIs against disorder, addressing the physics of Dirac and Weyl semimetals as a new research perspective in the field.

Density of states scaling at the semimetal to metal transition in three dimensional topological insulators.

The quantum phase transition between the three dimensional Dirac semimetal and the diffusive metal can be induced by increasing disorder. Taking the system of a disordered Z2 topological insulator as an important example, we compute the single particle density of states by the kernel polynomial method. We focus on three regions: the Dirac semimetal at the phase boundary between two topologically distinct phases, the tricritical point of the two topological insulator phases and the diffusive metal, and the diffusive metal lying at strong disorder. The density of states obeys a novel single parameter scaling, collapsing onto two branches of a universal scaling function, which correspond to the Dirac semimetal and the diffusive metal. The diverging length scale critical exponent ν and the dynamical critical exponent z are estimated, and found to differ significantly from those for the conventional Anderson transition. Critical behavior of experimentally observable quantities near and at the tricritical point is also discussed.

Disordered weak and strong topological insulators.

A global phase diagram of disordered weak and strong topological insulators is established numerically. As expected, the location of the phase boundaries is renormalized by disorder, a feature recognized in the study of the so-called topological Anderson insulator. Here, we report unexpected quantization, i.e., robustness against disorder of the conductance peaks on these phase boundaries. Another highlight of the work is on the emergence of two subregions in the weak topological insulator phase under disorder. According to the size dependence of the conductance, the surface states are either robust or "defeated" in the two subregions. The nature of the two distinct types of behavior is further revealed by studying the Lyapunov exponents.

Flat edge modes of graphene and of Z2 topological insulator.

A graphene nano-ribbon in the zigzag edge geometry exhibits a specific type of gapless edge modes with a partly flat band dispersion. We argue that the appearance of such edge modes are naturally understood by regarding graphene as the gapless limit of a Z2 topological insulator. To illustrate this idea, we consider both Kane-Mele (graphene-based) and Bernevig-Hughes-Zhang models: the latter is proposed for HgTe/CdTe 2D quantum well. Much focus is on the role of valley degrees of freedom, especially, on how they are projected onto and determine the 1D edge spectrum in different edge geometries.