Prognosis of Young Survivors of Gastric Cancer in China and the U.S.: Determining Long-Term Outcomes Based on Conditional Survival.

BACKGROUND: Young survivors of gastric cancer (GC) have better prognoses than elderly patients, yet their disease-specific survival (DSS) has received little attention. PATIENTS AND METHODS: Data on young patients (aged ≤40 years) with GC undergoing resections at three Chinese institutions (n = 542) and from the SEER database (n = 533) were retrospectively analyzed. Three-year conditional disease-specific survival (CS3) was assessed. The effects of well-known prognostic factors over time were analyzed by time-dependent Cox regression. RESULTS: Overall, young Chinese patients with GC had a better 5-year DSS than U.S. patients (62.8% vs. 54.1%; p < .05). The disease-specific mortality likelihood of the entire cohort was not constant over time, with most deaths occurring during the first 3 years after surgery but peaking at 1 and 2 years in China and the U.S., respectively. Based on 5-year survivorship, the CS3 rates of both groups were similar (90.9% [U.S.] vs. 91.5% [China]; p > .05). Cox regression showed that for Chinese patients, site, size, T stage, and N stage were independent prognostic factors at baseline (p < .05). For U.S. patients, grade, T stage. and N stage significantly affected DSS at baseline (p < .05). In both groups, only T stage continuously affected DSS within 3 years after gastrectomy. However, for both groups, the initial well-known prognostic factors lost prognostic significance after 5 years of survival (all p > .05). Although the 5-year DSS rates of young Chinese patients with T3 and T4a disease were significantly better than those of young U.S. patients, in each T stage, the CS3 of both regions trended toward consistency over time. CONCLUSION: For young patients with GC, the factors that predict survival at baseline vary over time. Although the initial 5-year DSS is heterogeneous, insight into conditional survival will help clinicians evaluate the long-term prognoses of survivors while ignoring population differences. IMPLICATIONS FOR PRACTICE: With the increasing number of young survivors of gastric cancer (GC), it is essential for clinicians to understand the dynamic prognosis of these patients. Based on large data sets from China and the U.S., this study found that the prognostic factors that predict survival for young patients with GC at baseline vary over time. Although the initial 5-year disease-specific survival is heterogeneous, insight into conditional survival will help clinicians evaluate the long-term prognoses of survivors while ignoring population differences. This knowledge may be more effective in helping young patients with GC to manage future uncertainties, especially when they need to make important life plans.

Optimization and feedback control system of dilution rate for 1,3-propanediol in two-stage fermentation: A theoretical study.

In utilizing glycerol to produce 1,3-propanediol by microbial fermentation, the problems of low utilization rate and poor production performance need to be addressed. Based on the analysis of a mathematical model for 1,3-propanediol production from glycerol by Klebsiella pneumoniae, this study theoretically investigated the effects of the dilution rate and the initial glycerol concentration in a two-stage fermentation process and the feasibility of applying the feedback control methods. First, the optimal operation conditions of initial glycerol concentration and dilution rate were obtained. Through the use of feedback control theory, a control strategy for dilution rate was designed and optimized to shorten the settling time (time required for fermentation to reach stability) from 60.92 to 36.68 h for the first reactor, and from 53.66 to 22.68 h for the second reactor. In addition, the yield of 1,3-propanediol in both two reactors reached up to 0.5 g·g-1 . The simulation results indicated that the feedback control strategy for dilution rate increased the product concentration, reduced the residual glycerol in the fermentation broth, and greatly improved the performance of the fermentation. A feeding strategy of automatic control for dilution rate has been established and will be applied as an effective guiding scheme in automatic continuous fermentations for production of 1,3-propanediol.

Invasion entire solutions in a time periodic Lotka-Volterra competition system with diffusion.

This paper is concerned with invasion entire solutions of a monostable time periodic Lotka-Volterra competition-diffusion system. We first give the asymptotic behaviors of time periodic traveling wave solutions at infinity by a dynamical approach coupled with the two-sided Laplace transform. According to these asymptotic behaviors, we then obtain some key estimates which are crucial for the construction of an appropriate pair of sub-super solutions. Finally, using the sub-super solutions method and comparison principle, we establish the existence of invasion entire solutions which behave as two periodic traveling fronts with different speeds propagating from both sides of x-axis. In other words, we formulate a new invasion way of the superior species to the inferior one in a time periodic environment.