In this article, we show the general relation between standardization methods and marginal structural models. Standardization has been recognized as a method to control confounding and to estimate causal parameters of interest. Because standardization requires stratification by confounders, the sparse-data problem will occur when stratified by many confounders and one then might have an unstable estimator. A new class of causal models called marginal structural models has recently been proposed. In marginal structural models, the parameters are consistently estimated by the inverse-probability-of-treatment weighting method. Marginal structural models give a nonparametric standardization using the total group (exposed and unexposed) as the standard. In epidemiologic analysis, it is also important to know the change in the average risk of the exposed (or the unexposed) subgroup produced by exposure, which corresponds to the exposed (or the unexposed) group as the standard. We propose modifications of the weights in the marginal structural models, which give the nonparametric estimation of standardized parameters. With the proposed weights, we can use the marginal structural models as a useful tool for the nonparametric multivariate standardization.

189 Background: Despite improvements of postoperative adjuvant therapy for resected pancreatic ductal adenocarcinoma (PDAC), its prognosis remains poor. A randomized controlled trial has begun to compare neoadjuvant chemotherapy using gemcitabine and S1 (NAC-GS) with upfront surgery (Up-S) for patients with PDAC planned resection. Methods: Patients were enrolled after the diagnosis of resectable PDAC with histological confirmation. They were randomly assigned as either NAC-GS or Up-S. In NAC-GS, gemcitabine was provided at a dose of 1 g/m2 on day 1 and 8 and oral S-1 was administered at a dose of 40 mg/m2 twice daily on 1-14 days. Patients received 2 cycles of this regimen. S-1 adjuvant for 6 months was administered for the patients with curative resection and fully recovered within 10 weeks after surgery in both arms. The primary endpoint for the phase III part was overall survival (OS); secondary endpoints included adverse events, resection rate, recurrence-free survival, residual tumor status, nodal metastases, and tumor marker kinetics. The target sample size required 163 patients (α-error 0.05; power 0.8) in each arm. The trial was conducted by the Health Labor Sciences Research Grant (H22-009) of Japan and registered with the UMIN Clinical Trials Registry as UMIN000009634. Results: From January 2013 to January 2016, 364 patients were enrolled in 57 centers (182 to NAC-GS and 182 to Up-S). Of these, two were excluded because of ineligibility, therefore 182 patients in NAC-GS and 180 in Up-S constituted the ITT analysis-set. The median OS was 36.7 months in NAC-GS and 26.6 months in Up-S; HR 0.72 (95% confidential interval 0.55-0.94; p=0.015 [stratified log-rank test]). Grade 3 or 4 adverse events frequently (72.8%) observed in NAC-GS were leukopenia or neutropenia. However, the resection rate, R0 resection rate, and morbidity of the operation were equivalent in the two groups. There was no perioperative mortality in either group. Conclusions: This phase III study demonstrated the significant survival benefits of NAC-GS treatment. Therefore, the results indicated that neoadjuvant chemotherapy could be a new standard for patients with resectable PDAC. Clinical trial information: UMIN000009634.

BackgroundThe high recurrence rate after surgery for colorectal cancer liver metastasis (CLM) remains a crucial problem. The aim of this trial was to evaluate the efficacy of adjuvant therapy with uracil-tegafur and leucovorin (UFT/LV).MethodsIn the multicenter, open-label, phase III trial, patients undergoing curative resection of CLM were randomly assigned in a 1:1 ratio to either the UFT/LV group or surgery alone group. The UFT/LV group orally received 5 cycles of adjuvant UFT/LV (UFT 300mg/m2 and LV 75mg/day for 28 days followed by a 7-day rest per cycle). The primary endpoint was recurrence-free survival (RFS). Secondary endpoints included overall survival (OS).ResultsBetween February 2004 and December 2010, 180 patients (90 in each group) were enrolled into the study. Of these, 3 patients (2 in the UFT/LV group and 1 in the surgery alone group) were excluded from the efficacy analysis. Median follow-up was 4.76 (range, 0.15–9.84) years. The RFS rate at 3 years was higher in the UFT/LV group (38.6%, n = 88) than in the surgery alone group (32.3%, n = 89). The median RFS in the UFT/LV and surgery alone groups were 1.45 years and 0.70 years, respectively. UFT/LV significantly prolonged the RFS compared with surgery alone with the hazard ratio of 0.56 (95% confidence interval, 0.38–0.83; P = 0.003). The hazard ratio for death of the UFT/LV group against the surgery alone group was not significant (0.80; 95% confidence interval, 0.48–1.35; P = 0.409).ConclusionAdjuvant therapy with UFT/LV effectively prolongs RFS after hepatic resection for CLM and can be recommended as an alternative choice.Trial RegistrationUMIN Clinical Trials Registry C000000013

Our simulation study demonstrated that the intrinsic rate of missing and error of linkage variables was key to choosing between linkage methods. In general, probabilistic linkage was a better choice, but for exceptionally good quality data (<5% error), deterministic linkage was a more resource efficient choice.

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Frequent recurrence of hepatocellular carcinoma (HCC) after surgery remains a major clinical problem. This randomized controlled trial evaluated whether postoperative adjuvant therapy with oral uracil-tegafur (UFT) prevents recurrence of HCC. A total of 160 patients who underwent curative hepatic resection for HCC were randomly assigned to receive either 300 mg/day of UFT for 1 year after surgery (n ‫؍‬ 79, UFT group) or surgery alone (n ‫؍‬ 80, control group). The primary endpoint was recurrence-free survival, and the secondary endpoint was overall survival. Other study variables included liver function and type of recurrence. During a median follow-up of 4.8 years (range: 0.5-7.9), recurrence-free survival curves in the groups were similar (P ‫؍‬ .87). Overall survival was slightly but not significantly worse in the UFT group than in the control group (P ‫؍‬ .08). The rates of recurrence-free and overall survival at 5 years were 29% and 58%, respectively, in the UFT group, as compared with 29% and 73%, respectively, in the control group. The hazard ratio for recurrence in the UFT group, relative to the control, was 1.01 (95% confidence interval: 0.84-1.22, P ‫؍‬ .87). The proportion of patients with advanced recurrence (i.e., multiple, extrahepatic, or associated with vascular invasion) was significantly higher in the UFT group (74%, 43 of 58 patients with recurrence) than in the control group (53%, 30 of 57) (P ‫؍‬ .02). In conclusion, our results offer no evidence to support potential benefits of adjuvant chemotherapy with UFT after surgery in patients with HCC and suggest that such treatment may even worsen overall survival. (HEPATOLOGY 2006;44:891-895.)

The present study demonstrates that an iCBT program is effective in preventing MDE in the working population. However, it should be noted that MDE was measured by self-report, while the CIDI can measure the episodes more strictly following DSM-IV criteria.

We develop the randomized analysis for repeated binary outcomes with non-compliance. A break randomization-based semi-parametric estimation procedure for both the causal risk difference and the causal risk ratio is proposed for repeated binary data. Although we assume the simple structural models for potential outcomes, we choose to avoid making any assumptions about comparability beyond those implied by randomization at time zero. The proposed methods can incorporate non-compliance information, while preserving the validity of the test of the null hypothesis, and even in the presence of non-random non-compliance can give the estimate of the causal effect that treatment would have if all individuals complied with their assigned treatment. The methods are applied to data from a randomized clinical trial for reduction of febrile neutropenia events among acute myeloid leukaemia patients, in which a prophylactic use of macrophage colony-stimulating factor (M-CSF) was compared to placebo during the courses of intensive chemotherapies.