Treatment of hilar cholangiocarcinoma (Klatskin tumors) with hepatic resection or transplantation

Background: Because of the rarity of hilar cholangiocarcinoma, its prognostic risk factors have not been sufficiently analyzed. This retrospective study was undertaken to evaluate various pathologic risk factors which influenced survival after curative hepatic resection or transplantation. Methods: Between 1981 and 1996, 72 patients (43 males and 29 females) with hilar cholangiocarcinoma underwent hepatic resection (34 patients) or transplantation (38 patients) with curative intent. Medical records and pathologic specimens were reviewed to examine the various prognostic risk factors. Survival was calculated by the method of Kaplan- Meier using the log rank test with adjustment for the type of operation. Survival statistics were calculated first for each kind of treatment separately, and then combined for the calculation of the final significance value. Results: Survival rates for 1, 3, and 5 years after hepatic resection were 74%, 34%, and 9%, respectively, and those after transplantation were 60%, 32%, and 25%, respectively. Univariate analysis revealed that T-3, positive lymph nodes, positive surgical margins, and pTNM stage III and IV were statistically significant poor prognostic factors. Multivariate analysis revealed that pTNM stage 0, I, and II, negative lymph node, and negative surgical margins were statistically significant good prognostic factors. For the patients in pTNM stage 0-II with negative surgical margins, 1-, 3-, and 5-year survivals were 80%, 73%, and 73%, respectively. For patients in pTNM stage IV-A with negative lymph nodes and surgical margins, 1-, 3-, and 5- year survivals were 66%, 37%, and 37%, respectively. Conclusions: Satisfactory longterm survivals can be obtained by curative surgery for hilar cholangiocarcinoma either with hepatic resection or liver transplantation. Redefining pTNM stage III and IV-A is proposed to better define prognosis

Hepatic resection and transplantation for peripheral cholangiocarcinoma

Background: Recent publications have questioned the role of orthotopic liver transplantation (OLT) in treating advanced or unresectable peripheral cholangiocarcinoma (Ch-Ca). Study Design: We reviewed our experience with Ch- Ca to determine survival rates, recurrence patterns, and risk factors in 54 patients who underwent either hepatic resection or OLT between 1981 and 1994. Liver transplantation was performed in patients with unresectable tumors (n = 12) and in those with advanced cirrhosis (n = 8). There were 33 women (61%) and 21 men (39%), with a mean age of 54.3 years. The median followup period was 6.8 years. Prognostic risk factors were analyzed by univariate and multivariate analyses. Results: Mortality within 30 days was 7.4%. Overall patient and tumor-free survival rates were 64% and 57% at 1 year, 34% and 34% at 3 years, and 26% and 27% at 5 years after operation. Thirty-two patients (59.3%) experienced tumor recurrence. Univariate analysis revealed that multiple tumors, bilobar tumor distribution, regional lymph node involvement, presence of metastasis, positive surgical margins, and advanced pTNM stages were significant negative predictors of both tumor-free and patient survival. Multivariate analysis revealed that positive margins, multiple tumors, and lymph node involvement were independently associated with poor prognosis. When patients with these three negative predictors were excluded, the patient survivals at 1, 3, and 5 years were 74%, 64%, and 62%, respectively. Conclusions: Both hepatic resection and OLT are effective therapies for Ch- Ca when the tumor can be removed with adequate margins, the lesion is singular, and lymph nodes are not involved

Evolution of Surface Roughness in Grinding and its Relationship with the Dressing Parameters and the Radial Wear

Grinding is a machining process specially indicated for finishing operations in hard materials, in order to obtain low surface roughness (Ra 0.1 μm to 2μm) and tight tolerances. The cutting tool is the grinding wheel which is formed by abrasive particles attached in a bond. The wear of these abrasive particles modifies significantly the roughness obtained in the workpiece. In this work, the evolution of part roughness has been continuously monitored as the grinding process progresses and the wheel gets worn. The roughness evolution is then related to different process variables such as the dressing parameters, the grinding conditions, the grinding forces and the radial wear of the wheel

Hepatic resection for metastatic colorectal adenocarcinoma: A proposal of a prognostic scoring system

Background: Hepatic resection for metastatic colorectal cancer provides excellent longterm results in a substantial proportion of patients. Although various prognostic risk factors have been identified, there has been no dependable staging or prognostic scoring system for metastatic hepatic tumors. Study Design: Various clinical and pathologic risk factors were examined in 305 consecutive patients who underwent primary hepatic resections for metastatic colorectal cancer. Survival rates were estimated by the Cox proportional hazards model using the equation: S(t) = [S(o)(t)](exp(R - R(o))), where S(o)(t) is the survival rate of patients with none of the identified risk factors and R(o) = 0. Results: Preliminary multivariate analysis revealed that independently significant negative prognosticators were: (1) positive surgical margins, (2) extrahepatic tumor involvement including the lymph node(s), (3) tumor number of three or more, (4) bilobar tumors, and (5) time from treatment of the primary tumor to hepatic recurrence of 30 months or less. Because the survival rates of the 62 patients with positive margins or extrahepatic tumor were uniformly very poor, multivariate analysis was repeated in the remaining 243 patients who did not have these lethal risk factors. The reanalysis revealed that independently significant poor prognosticators were: (1) tumor number of three or more, (2) tumor size greater than 8 cm, (3) time to hepatic recurrence of 30 months or less, and (4) bilobar tumors. Risk scores (R) for tumor recurrence of the culled cohort (n = 243) were calculated by summation of coefficients from the multivariate analysis and were divided into five groups: grade 1, no risk factors (R = 0); grade 2, one risk factor (R = 0.3 to 0.7); grade 3, two risk factors (R = 0.7 to 1.1); grade 4, three risk factors (R = 1.2 to 1.6); and grade 5, four risk factors (R > 1.6). Grade 6 consisted of the 62 culled patients with positive margins or extrahepatic tumor. Kaplan-Meier and Cox proportional hazards estimated 5-year survival rates of grade 1 to 6 patients were 48.3% and 48.3%, 36.6% and 33.7%, 19.9% and 17.9%, 11.9% and 6.4%, 0% and 1.1%, and 0% and 0%, respectively (p < 0.0001). Conclusions: The proposed risk-score grading predicted the survival differences extremely well. Estimated survival as determined by the Cox proportional hazards model was similar to that determined by the Kaplan-Meier method. Verification and further improvements of the proposed system are awaited by other centers or international collaborative studies

LCL Grid Filter Design of a Multimegawatt Medium-Voltage Converter for Offshore Wind Turbine Using SHEPWM Modulation

The switching frequency of medium-voltage highpower converters is limited to about 1 kHz due to semiconductor junction temperature constraint. The frequency band between the fundamental and carrier frequency is limited to a little more than one decade and the LCL filter design is usually a challenge to meet grid codes for grid-connected applications. Traditional designs focus on the optimization of the filter parameters and different damping circuits. However, this design is very influenced by the modulation technique and produced low-order harmonics. Widely used pulse width modulations (PWM), such as phase disposition PWM (PDPWM), produce low-order harmonics that constraint the design of the filter. Selective harmonic elimination PWM (SHEPWM) can eliminate theses low-order harmonics, enabling a more efficient design of the LCL filter. In this paper, the LCL grid filter of a multimegawatt medium-voltage neutral-point-clamped converter for a wind turbine is redesigned using the SHEPWM modulation. Experimental results demonstrate that the efficiency of the converter, filter, and overall efficiency are increased compared to that obtained with PDPWM

Adaptability and Genotype x Environment Interaction of Spring Wheat Cultivars in Chile using Regression Analysis, AMMI, and SRAG.

del Pozo, A (del Pozo, Alejandro). Univ Talca, Fac Ciencias Agr, Talca, ChileWheat (Triticum aestivum L.) genetic improvement objectives include obtaining cultivars capable of expressing their maximum potential yield and quality in diverse environments. This make necessary to know and define the environment in which a variety can express its maximum potential yield and quality. The objective of this study was to assess which method is the most efficient to study cultivars response in multiple environments. For this, we analyze the adaptability, stability, and genotype x environment (GxE) interaction effect, grain yield, sedimentation, and wet gluten content of 13 spring wheat cultivars sown in six environments in the central-south and southern zones of Chile during two seasons. The data were analyzed by regression analysis, additive main effects and multiplicative interaction (AMMI), and the sites regression (SREG) model. By this was thus established that SREG analysis is the most efficient for this type of study since, in addition to analyzing stability, adaptability, and effect (GxE), it allows identifying the best cultivar. In this case, `Pandora-INIA' stands out by exhibiting the best yield (7.38 t ha(-1)), high sedimentation (36.95 cm(3)), and wet gluten (41.54%) indices in all the environments, and this positions it as a variety having both high yield and quality

Liver transplantation for hepatocellular carcinoma: A proposal of a prognostic scoring system

Background: The current staging system of hepatocellular carcinoma established by the International Union Against Cancer and the American Joint Committee on Cancer does not necessarily predict the outcomes after hepatic resection or transplantation. Study Design: Various clinical and pathologic risk factors for tumor recurrence were examined on 344 consecutive patients who received hepatic transplantation in the presence of nonfibrolamellar hepatocellular carcinoma to establish a reliable risk scoring system. Results: Multivariate analysis identified three factors as independently significant poor prognosticators: 1) bilobarly distributed tumors, 2) size of the greatest tumor (2 to 5 cm and > 5 cm), and 3) vascular invasion (microscopic and macroscopic). Prognostic risk score (PRS) of each patient was calculated from the relative risks of multivariate analysis. The patients were grouped into five grades of tumor recurrence risk: grade 1: PRS = 0 to 11.0 to 15.0; grade 4: PRS ≥ 15.0; and grade 5: positive node, metastasis, or margin. The proposed PRS system correlated extremely well with tumor-free survival after liver transplantation (100%, 61%, 40%, 5%, and 0%, from grades 1 to 5, respectively, at 5 years), but current pTNM staging did not. Conclusions: 1) Patients with grades 1 and 2 are effectively treated with liver transplantation, 2) patients with grades 4 and 5 are poor candidates for liver transplantation, and 3) patients with grade 1 do not benefit from adjuvant chemotherapy. (C) 2000 by the American College of Surgeons