Temperature Field, Flow Field, and Temporal Fluctuations Thereof in Ammonothermal Growth of Bulk GaN-Transition from Dissolution Stage to Growth Stage Conditions.

With the ammonothermal method, one of the most promising technologies for scalable, cost-effective production of bulk single crystals of the wide bandgap semiconductor GaN is investigated. Specifically, etch-back and growth conditions, as well as the transition from the former to the latter, are studied using a 2D axis symmetrical numerical model. In addition, experimental crystal growth results are analyzed in terms of etch-back and crystal growth rates as a function of vertical seed position. The numerical results of internal process conditions are discussed. Variations along the vertical axis of the autoclave are analyzed using both numerical and experimental data. During the transition from quasi-stable conditions of the dissolution stage (etch-back process) to quasi-stable conditions of the growth stage, significant temperature differences of 20 K to 70 K (depending on vertical position) occur temporarily between the crystals and the surrounding fluid. These lead to maximum rates of seed temperature change of 2.5 K/min to 1.2 K/min depending on vertical position. Based on temperature differences between seeds, fluid, and autoclave wall upon the end of the set temperature inversion process, deposition of GaN is expected to be favored on the bottom seed. The temporarily observed differences between the mean temperature of each crystal and its fluid surrounding diminish about 2 h after reaching constant set temperatures imposed at the outer autoclave wall, whereas approximately quasi-stable conditions are reached about 3 h after reaching constant set temperatures. Short-term fluctuations in temperature are mostly due to fluctuations in velocity magnitude, usually with only minor variations in the flow direction.

High-Energy Computed Tomography as a Prospective Tool for In Situ Monitoring of Mass Transfer Processes inside High-Pressure Reactors-A Case Study on Ammonothermal Bulk Crystal Growth of Nitrides including GaN.

For the fundamental understanding and the technological development of the ammonothermal method for the synthesis and crystal growth of nitrides, an in situ monitoring technique for tracking mass transport of the nitride throughout the entire autoclave volume is desirable. The feasibility of using high-energy computed tomography for this purpose was therefore evaluated using ex situ measurements. Acceleration voltages of 600 kV were estimated to yield suitable transparency in a lab-scale ammonothermal setup for GaN crystal growth designed for up to 300 MPa operating pressure. The total scan duration was estimated to be in the order of 20 to 40 min, which was sufficient given the comparatively slow crystal growth speed in ammonothermal growth. Even shorter scan durations or, alternatively, lower acceleration voltages for improved contrast or reduced X-ray shielding requirements, were estimated to be feasible in the case of ammonoacidic growth, as the lower pressure requirements for this process variant allow for thinned autoclave walls in an adapted setup designed for improved X-ray transparency. Promising nickel-base and cobalt-base alloys for applications in ammonothermal reactors with reduced X-ray absorption in relation to the maximum operating pressure were identified. The applicability for the validation of numerical simulations of the growth process of GaN, in addition to the applicability of the technique to further nitride materials, as well as larger reactors and bulk crystals, were evaluated.

Differences in disease status between patients with progression after first-line chemotherapy versus early relapse after adjuvant chemotherapy who undergo second-line chemotherapy for gastric cancer: Exploratory analysis of the randomized phase III TRICS trial.

BACKGROUND: Second-line chemotherapy (SLC) improves survival in advanced gastric cancer (AGC). Patients receiving SLC are categorized into two disease status groups: tumour progression after first-line chemotherapy and early recurrence after adjuvant chemotherapy. Differences between these groups have not yet been clarified. PATIENTS AND METHODS: A total of 163 eligible patients registered in the randomized phase III TRICS trial evaluating SLC for patients with AGC was classified into the progressive disease (PD) group (n = 55) or the early relapse (ER) group (n = 108). We compared overall survival (OS), progression-free survival (PFS), overall response rate (ORR), and safety. Adjusted OS and adjusted PFS were estimated using inverse probability of treatment weighting (IPTW). RESULTS: The ER group had a lower median age than the PD group (66 vs. 72 years; P = 0.016), performance status (PS) 0 was more frequently seen in the ER group (87% vs. 71%; P = 0.012). The adjusted median OS was 13.7 months in the ER group and 13.6 months in the PD group (IPTW hazard ratio [HR]: 1.023; P = 0.854). The adjusted median PFS was 4.9 months in the ER group and 4.4 months in the PD group (IPTW HR: 0.707; P = 0.004). ORR was significantly better in the ER group than the PD group (21.3% vs. 4.9%; P = 0.020). No significant differences were observed in the incidence of adverse events. CONCLUSIONS: ER was associated with improved PFS and better ORR than PD, although no difference in survival was demonstrated. From the viewpoint of treatment outcome, it seems appropriate to treat patients with ER in the same way as patients with PD. CLINICAL TRIAL REGISTRATION: UMIN 000002571.

A study of second-line irinotecan plus cisplatin vs. irinotecan alone in platinum-naïve patients with early relapse of gastric cancer refractory to adjuvant S-1 monotherapy: exploratory subgroup analysis of the randomized phase III TRICS trial.

BACKGROUNDS: Many patients with gastric cancer relapse during or early after adjuvant chemotherapy. The standard treatment for early relapse patients is a second-line chemotherapy (SLC) based on irinotecan, taxanes, or a platinum-based chemotherapy. The platinum-containing biweekly irinotecan plus cisplatin (IRI/CDDP) combination was assumed to be promising in several reports of clinical trials as SLC. TRICS trial, a randomized phase III study of IRI/CDDP vs. IRI in platinum-naïve gastric cancers refractory to S-1 monotherapy, revealed that both irinotecan-based chemotherapies were effective and well tolerated. METHODS: This study analyzed 108 patients in the TRICS trial who experienced early relapse. Patients receiving IRI/CDDP (IRI, 60 mg/m2; CDDP, 30 mg/m2, q2w) versus IRI (150 mg/m2, q2w) were compared regarding overall survival (OS), progression-free survival (PFS), overall response rate (ORR), and safety. RESULTS: The OS was 14.0 (95% confidence interval [CI]: 11.0-21.2) and 14.0 (95% CI: 10.7-16.5) months for IRI/CDDP and IRI, respectively (hazard ratio [HR]: 0.782; 95% CI: 0.515-1.188, P = 0.249). No significant differences were observed for PFS (5.0 vs. 4.5 months, respectively; HR: 0.802; 95% CI: 0.543-1.185, P = 0.268) or ORR (19.6% [95% CI: 9.4-33.9%] vs. 23.3% [95% CI: 11.8-38.6%], respectively). The incidence of grade 3-4 anemia was higher for IRI/CDDP than for IRI (20% vs. 0%, respectively; P = 0.0006). CONCLUSION: Our study showed no significant survival differences between IRI/CDDP and IRI in platinum-naïve patients who relapsed during or within 6 months after S-1 adjuvant therapy; therefore, IRI may be a good option in this population. CLINICAL TRIAL INFORMATION: UMIN 000002571.

Randomised phase III trial of second-line irinotecan plus cisplatin versus irinotecan alone in patients with advanced gastric cancer refractory to S-1 monotherapy: TRICS trial.

AIM: The optimal second-line regimen for treating advanced gastric cancer (AGC) remains unclear. While irinotecan (CPT-11) plus cisplatin (CDDP) combination therapy and CPT-11 monotherapy have been explored in the second-line setting, the superiority of second-line platinum-based therapies for AGC patients initially treated with S-1 monotherapy has not yet been evaluated; therefore, we aimed to examine the survival benefit of CPT-11/CDDP combination over CPT-11 monotherapy. METHODS: AGC patients showing progression after S-1 monotherapy for advanced cancer or recurrence within 6 months after completion of S-1 adjuvant therapy were randomly allocated to CPT-11/CDDP (CPT-11, 60 mg/m(2); CDDP, 30 mg/m(2), q2w) or CPT-11 (150 mg/m(2), q2w). RESULTS: Sixty-eight advanced and 95 recurrent cases were evaluated. The median overall survivals were 13.9 (95% confidence interval [CI]: 10.8-17.6) and 12.7 (95% CI: 10.3-17.2) months for CPT-11/CDDP and CPT-11, respectively (hazard ratio: 0.834; 95% CI: 0.596-1.167, P = 0.288). No significant differences were observed in the secondary end-points, including progression-free survival (4.6 [95% CI: 3.4-5.9] versus 4.1 [95% CI: 3.3-4.9]months) and response rate (16.9% [95% CI: 8.8-28.3] versus 15.4% [95% CI: 7.6-26.5]). The incidences of grade 3-4 anaemia (16% versus 4%) and elevated serum lactate dehydrogenase levels (5% versus 0%) were higher for CPT-11/CDDP than for CPT-11. Exploratory subgroup analysis revealed that CPT-11/CDDP was significantly more effective for intestinal-type AGC, compared with CPT-11 (overall survival: 15.8 versus 14.0 months; P = 0.019). CONCLUSION: No survival benefit was observed upon adding CDDP to CPT-11 after S-1 monotherapy failure.

Prediction of metastasis to mesorectal, internal iliac and obturator lymph nodes according to size criteria in patients with locally advanced lower rectal cancer.

OBJECTIVE: This study was performed to clarify whether size criteria could be applied to the prediction of metastasis to the mesorectal, internal iliac and obturator lymph nodes in patients with lower rectal cancer. METHODS: A total of 915 lymph nodes (416 mesorectal, 199 internal iliac and 300 obturator) from 53 patients with lower rectal cancer who underwent a curative resection were examined; 83 lymph nodes were positive. The sizes of the lymph nodes immediately after removal and those of paraffin-embedded sections were compared for 175 lymph nodes. Then, size criteria for discriminating the status of metastasis were evaluated in 915 paraffin-embedded lymph nodes. RESULTS: Regardless of the metastatic status and the site of the lymph nodes, a positive relationship was observed between the sizes of the lymph nodes immediately after removal and those of paraffin-embedded sections (P < 0.01). The area under the curve generated by a receiver-operating characteristics curve showed no significant differences between the short-axis diameter and the long-axis diameter, regardless of the lymph node location. Specifically, the optimal cutoff value of the short-axis diameter for discriminating the status of metastasis in mesorectal, internal iliac and obturator lymph nodes extrapolated to the living body was set at 6.2, 5.0 and 4.8 mm, with accuracies of 72.4, 63.8 and 59.3% and with positive predictive values of 29.9, 16.3 and 7.1%, respectively. CONCLUSIONS: Size criteria were applicable for discriminating the metastatic status of lymph nodes from three different locations, although the positive predictive values of the size criteria for the internal iliac and obturator lymph nodes were lower than that for the mesorectal lymph nodes.

Curative resection of transverse colon cancer via minilaparotomy.

Minilaparotomy has been reported to be a minimally invasive alternative to laparoscopically assisted surgery. We retrospectively evaluated the usefulness of minilaparotomy for the resection of transverse colon cancer, which has generally been considered difficult to resect laparoscopically. Patients for whom curative resection was attempted for transverse colon cancer (n = 21) or sigmoid colon cancer (n = 81) via minilaparotomy (skin incision, < or = 7cm) were analyzed. The 2 groups did not significantly differ in terms of success rate of minilaparotomy (90.5% versus 97.5%), age, sex, pathologic stage, body mass index, operative time (mean, 133.5 minutes versus 122.5 minutes), blood loss (119.7 mL versus 92.4 mL), number of lymph nodes harvested, incidence of postoperative complications (9.5% versus 12.3%), postoperative length of stay, and 5-year disease-free survival rate (86.6% versus 79.6%). Minilaparotomy is feasible, safe, and favorable in terms of early oncologic outcome in patients with transverse colon cancer as well as those with sigmoid colon cancer.

Impact of prior abdominal surgery on curative resection of colon cancer via minilaparotomy.

PURPOSE: To evaluate the impact of prior abdominal surgery on curative resection of colon cancer via a minilaparotomy approach. METHODS: Feasibility, safety, and oncological outcomes were evaluated retrospectively in 263 patients scheduled to undergo curative resection of colon cancer via a minilaparotomy approach, defined as a skin incision of ≤ 7 cm, between September 2000 and March 2009. RESULTS: Abdominal adhesions were found in 59 (77.6%) of 76 patients who had undergone prior abdominal surgery (PAS group) and in 4 (2.1%) of 187 patients who had not (control group). The success rate of the minilaparotomy approach was 92.1% in the PAS group and 97.3% in the control group (P = 0.08). The incidence of extending the minilaparotomy wound for adhesiolysis was significantly higher in the PAS group than in the control group (6.6% vs 0.5%; P < 0.01). The two groups did not differ significantly in terms of the types of surgery, pathological stage, body mass index, operative time, blood loss, incidence of postoperative complications, length of postoperative hospital stay, and disease-free survival. CONCLUSIONS: These results suggest that prior abdominal surgery might require an extension of the minilaparotomy incision but that it does not seem to contraindicate a minilaparotomy approach for curative colectomy.