Validation of surrogate endpoints in cancer clinical trials via principal stratification with an application to a prostate cancer trial

Increasing attention has been focused on the use and validation of surrogate endpoints in cancer clinical trials. Previous literature on validation of surrogate endpoints are classified into four approaches: the proportion explained approach; the indirect effects approach; the meta-analytic approach; and the principal stratification approach. The mainstream in cancer research has seen the application of a meta-analytic approach. However, VanderWeele (2013) showed that all four of these approaches potentially suffer from the surrogate paradox. It was also shown that, if a principal surrogate satisfies additional criteria called one-sided average causal sufficiency, the surrogate cannot exhibit a surrogate paradox. Here, we propose a method for estimating principal effects under a monotonicity assumption. Specifically, we consider cancer clinical trials which compare a binary surrogate endpoint and a time-to-event clinical endpoint under two naturally ordered treatments (e.g. combined therapy vs. monotherapy). Estimation based on a mean score estimating equation will be implemented by the expectation-maximization algorithm. We will also apply the proposed method as well as other surrogacy criteria to evaluate the surrogacy of prostate-specific antigen using data from a phase III advanced prostate cancer trial, clarifying the complementary roles of both the principal stratification and meta-analytic approaches in the evaluation of surrogate endpoints in cancer. Copyright © 2017 John Wiley & Sons, Ltd.

The Impact of Treatment Preferences in Second-Line Chemotherapy on the Prognosis of HER2-Negative Metastatic Breast Cancer

OBJECTIVE

We assessed the impact of treatment preferences in second-line chemotherapy on breast cancer prognosis using the SELECT BC study.

METHODS

The SELECT BC study was performed in patients with HER2-negative metastatic breast cancer treated with initial chemotherapy. From these patients, 618 were assigned to 2 groups (S-1 group, 309; taxane group, 309). The S-1 and taxane groups were each subdivided into 3 groups: crossover group, protocol-recommended group, and other group, and the analysis of overall survival (OS) was performed using Cox regression with inverse probability weighting, to adjust for postrandomization confounding.

RESULTS

In the taxane group, the OS of the crossover group (39.6 months) was better than that of the protocol-recommended group (35.7 months) and the other chemotherapy group (36.9 months) (vs. the protocol-recommended group, HR 0.72 [95% CI 0.52-0.98], p = 0.037; vs. the other chemotherapy group, HR 0.71 [95% CI 0.43-1.18], p = 0.183). In the S-1 group, there was no statistically significant difference in OS between the 3 groups.

CONCLUSION

The study of the combination of first-line chemotherapy and second-line chemotherapy showed that S-1 might be recommended as a second-line chemotherapy in patients in whom taxane was the primary chemotherapy.

Liver resection for hepatocellular carcinoma associated with hepatic vein invasion: A Japanese nationwide survey

Because of the rarity of hepatic vein tumor thrombus (HVTT) compared with portal vein tumor thrombus (PVTT) in patients with hepatocellular carcinoma, little is known about this disease entity. The aim of this study was to evaluate the prognosis of each treatment modality for HVTT through an analysis of data collected in a Japanese nationwide survey. We analyzed data for 1,021 Child-Pugh A hepatocellular carcinoma patients with HVTT without inferior vena cava invasion registered between 2000 and 2007. Of these patients, 540 who underwent liver resection (LR) and 481 who received other treatments were compared. Propensity scores were calculated, and we successfully matched 223 patients (49.0% of the LR group). The median survival time in the LR group was 2.89 years longer than that in the non-LR group (4.47 versus 1.58 years, P < 0.001) and 1.61 years longer than that in the non-LR group (3.42 versus 1.81 years, P = 0.023) in a propensity score-matched cohort. After curative resection, median survival times were similar between patients with HVTT in the peripheral hepatic vein and those with HVTT in the major hepatic vein (4.85 versus 4.67 years, P = 0.974). In the LR group, the postoperative 90-day mortality rate was 3.4% (16 patients). In patients without PVTT, the median survival time was significantly better than that in patients with PVTT (5.67 versus 1.88 years, P < 0.001).

CONCLUSION

LR is associated with a good prognosis in hepatocellular carcinoma patients with HVTT, especially in patients without PVTT. (Hepatology 2017;66:510-517).

A randomized phase II study of gemcitabine plus Z-360, a CCK2 receptor-selective antagonist, in patients with metastatic pancreatic cancer as compared with gemcitabine plus placebo

Background

We investigated the efficacy and safety of 60, 120, or 240 mg of Z-360, which is a highly potent cholecystokinin2-receptor-selective antagonist, combined with gemcitabine in patients with metastatic pancreatic cancer.

Methods

Patients were randomly assigned in a 1:1:1:1 ratio to one of four treatment groups. Patients received 1000 mg/m² gemcitabine for each cycle and Z-360 tablets of 60 mg (GZ 60 mg group), 120, 240 mg or placebo tablets (Gem group) orally twice daily. The primary endpoint was overall survival (OS).

Results

The median OS was 1.3 months longer in the GZ 60 mg group compared with the Gem group (8.5 vs. 7.2 months) and the risk of death was reduced by 19% compared with the Gem group, although there were no statistically significant differences. The study treatments were well tolerated.

Conclusions

In this Phase II study, no statistically significant differences between the GZ groups and Gem group were detected in any analysis. However, Z-360 in dose of 60 mg tends to improve OS in patients with metastatic pancreatic cancer with low toxic effect. Further exploratory trials with other agents such as gemcitabine plus nab-paclitaxel might be beneficial.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-017-3351-4) contains supplementary material, which is available to authorized users.

Dental Status and Compression of Life Expectancy with Disability

This study examined whether the number of teeth contributes to the compression of morbidity, measured as a shortening of life expectancy with disability, an extension of healthy life expectancy, and overall life expectancy. A prospective cohort study was conducted. A self-reported baseline survey was given to 126,438 community-dwelling older people aged ≥65 y in Japan in 2010, and 85,161 (67.4%) responded. The onset of functional disability and all-cause mortality were followed up for 1,374 d (follow-up rate = 96.1%). A sex-stratified illness-death model was applied to estimate the adjusted hazard ratios (HRs) for 3 health transitions (healthy to dead, healthy to disabled, and disabled to dead). Absolute differences in life expectancy, healthy life expectancy, and life expectancy with disability according to the number of teeth were also estimated. Age, denture use, socioeconomic status, health status, and health behavior were adjusted. Compared with the edentulous participants, participants with ≥20 teeth had lower risks of transitioning from healthy to dead (adjusted HR, 0.58 [95% confidence interval (CI), 0.50-0.68] for men and 0.70 [95% CI, 0.57-0.85] for women) and from healthy to disabled (adjusted HR, 0.52 [95% CI, 0.44-0.61] for men and 0.58 [95% CI, 0.49-0.68] for women). They also transitioned from disabled to dead earlier (adjusted HR, 1.26 [95% CI, 0.99-1.60] for men and 2.42 [95% CI, 1.72-3.38] for women). Among the participants aged ≥85 y, those with ≥20 teeth had a longer life expectancy (men: +57 d; women: +15 d) and healthy life expectancy (men: +92 d; women: +70 d) and a shorter life expectancy with disability (men: -35 d; women: -55 d) compared with the edentulous participants. Similar associations were observed among the younger participants and those with 1 to 9 or 10 to 19 teeth. The presence of remaining teeth was associated with a significant compression of morbidity: older Japanese adults' life expectancy with disability was compressed by 35 to 55 d within the follow-up of 1,374 d.

On hazard ratio estimators by proportional hazards models in matched-pair cohort studies

Background

In matched-pair cohort studies with censored events, the hazard ratio (HR) may be of main interest. However, it is lesser known in epidemiologic literature that the partial maximum likelihood estimator of a common HR conditional on matched pairs is written in a simple form, namely, the ratio of the numbers of two pair-types. Moreover, because HR is a noncollapsible measure and its constancy across matched pairs is a restrictive assumption, marginal HR as “average” HR may be targeted more than conditional HR in analysis.

Methods

Based on its simple expression, we provided an alternative interpretation of the common HR estimator as the odds of the matched-pair analog of C-statistic for censored time-to-event data. Through simulations assuming proportional hazards within matched pairs, the influence of various censoring patterns on the marginal and common HR estimators of unstratified and stratified proportional hazards models, respectively, was evaluated. The methods were applied to a real propensity-score matched dataset from the Rotterdam tumor bank of primary breast cancer.

Results

We showed that stratified models unbiasedly estimated a common HR under the proportional hazards within matched pairs. However, the marginal HR estimator with robust variance estimator lacks interpretation as an “average” marginal HR even if censoring is unconditionally independent to event, unless no censoring occurs or no exposure effect is present. Furthermore, the exposure-dependent censoring biased the marginal HR estimator away from both conditional HR and an “average” marginal HR irrespective of whether exposure effect is present. From the matched Rotterdam dataset, we estimated HR for relapse-free survival of absence versus presence of chemotherapy; estimates (95% confidence interval) were 1.47 (1.18–1.83) for common HR and 1.33 (1.13–1.57) for marginal HR.

Conclusion

The simple expression of the common HR estimator would be a useful summary of exposure effect, which is less sensitive to censoring patterns than the marginal HR estimator. The common and the marginal HR estimators, both relying on distinct assumptions and interpretations, are complementary alternatives for each other.

Electronic supplementary material

The online version of this article (doi:10.1186/s12982-017-0060-8) contains supplementary material, which is available to authorized users.

Predictive ability of visit-to-visit variability in HbA1c and systolic blood pressure for the development of microalbuminuria and retinopathy in people with type 2 diabetes

AIMS

We explored whether visit-to-visit variability in both glycated hemoglobin (HbA1c) and systolic blood pressure (SBP) simultaneously predicted the development of microalbuminuria and retinopathy, and whether the predictive ability of these measurements changed according to mean HbA1c and SBP levels in people with type 2 diabetes.

METHODS

A retrospective observational cohort study was conducted on 243 type 2 diabetes patients with normoalbuminuria and 486 without retinopathy at the first visit and within 1year thereafter. The two cohorts were followed up from 1995 until 2012. Multivariate and stratified analyses were performed using Cox proportional hazard models.

RESULTS

Microalbuminuria developed in 84 patients and retinopathy in 108. Hazard ratios (HRs) for the development of microalbuminuria associated with the coefficient of variation (CV) and variation independent of mean (VIM) of both HbA1c and SBP significantly increased. In participants with a mean SBP <130mmHg, the HRs for the development of retinopathy associated with CV and VIM of HbA1c were abruptly elevated and significant compared with those with a mean SBP ≥130mmHg.

CONCLUSIONS

Visit-to-visit variability in both HbA1c and SBP simultaneously predict the development of microalbuminuria. HbA1c variability may predict the development of retinopathy when the mean SBP is normal (<130mmHg).

Impact of attenuated-signal plaque observed by intravascular ultrasound on vessel response after drug-eluting stent implantation

BACKGROUND AND AIMS

The aim of this study was to investigate the impact of attenuated-signal plaque (ASP) observed by intravascular ultrasound (IVUS) on vessel response after drug-eluting stent implantation.

METHODS

Data were derived from the IVUS cohort of the J-DESsERT trial comparing paclitaxel- and sirolimus-eluting stents. Serial IVUS analysis (pre- and post-intervention, and 8-month follow-up) was performed in 136 non-AMI lesions. ASP was defined as hypoechoic plaque with ultrasound attenuation without calcification. Calcified plaque (CP) was defined as brightly echoreflective plaque with acoustic shadowing. ASP and CP scores were calculated by grading their measured angle as 0 to 4 for 0°, <90°, 90-180°, 180-270° and >270°, respectively. The entire stented segment was analyzed at 1-mm intervals.

RESULTS

At pre-intervention, ASP was observed in 40.4% of lesions, and this group had greater % neointimal volume (%NIV) at follow-up than the no-ASP group (p = 0.011). ASP score at pre-intervention positively correlated with %NIV (p = 0.023). During the follow-up, ASP score significantly decreased (p < 0.001), and CP score significantly increased (p < 0.001), with a negative correlation between them (p < 0.001). A decrease in the ASP score was associated with less %NIV in PES (p = 0.031), but not in SES (p = 0.229).

CONCLUSIONS

The greater extent of plaque with IVUS-signal attenuation at pre-intervention and its persistence during follow-up were associated with neointimal proliferation, possibly representing sustained inflammatory status, depending on the type of DES used.

Nomogram predicting long-term survival after the diagnosis of intrahepatic recurrence of hepatocellular carcinoma following an initial liver resection

BACKGROUND

The aim of this study was to construct and validate a nomogram for predicting survival after the intrahepatic recurrence of hepatocellular carcinoma (HCC) following an initial hepatectomy.

METHODS

A primary cohort of 268 patients who underwent curative hepatectomy for HCC at Shinshu University Hospital between 1990 and 2010 was retrospectively studied. A nomogram was constructed based on independent prognostic factors for overall survival after recurrence. The predictive performance was evaluated using the concordance index (c-index) and a calibration curve. The nomogram was then externally validated in a cohort of patients from Tokyo University Hospital (n = 296).

RESULTS

In multivariate analysis, the following 5 variables were identified as independent predictors of overall survival and incorporated into the nomogram-Japan Integrated Stage score at initial liver resection, platelet count at initial liver resection, time until intrahepatic recurrence, vascular invasion at recurrence, and type of treatment used for intrahepatic recurrence. The nomogram had a c-index of 0.75 (95% confidence interval 0.60-0.85) for the Shinshu cohort and 0.71 (0.57-0.81) for the Tokyo cohort. The predicted 3- and 5-year survival probabilities corresponded well with the actual outcomes.

CONCLUSIONS

The established nomogram might be useful for estimating survival after the intrahepatic recurrence of HCC.

A randomized controlled trial to compare the effectiveness between surgery and radiofrequency ablation for hepatocellular carcinoma: SURF trial

TPS506

Background: Which is superior to treat hepatocellular carcinoma (HCC), surgery or percutaneous ablation? This has been one of the most important questions in clinical research of hepatology. However, it has long remained unanswered because it is difficult to approach, as we mentioned previously (Ann Surg 2008;247:557-8). Thus, in 2009, we started this multicenter study in Japan to reach a strong conclusion to the above question (UMIN:000001795). Methods: The major inclusion criteria are: tumor foci numbering three or fewer, and each measuring 3 cm or less); Child–Pugh score of 7 or less; aged between 20 and 79 years; and indications for either surgical resection or radiofrequency ablation (RFA), as described previously (Hepatol Res 2010;40:851-2). In the study design, we adopted two co-primary end-points: overall survival (OS) and recurrence-free survival (RFS). If assuming 3-year RFS following surgery and RFA are assumed as 45% and 35%, respectively, 600 cases are regarded as necessary. Because 600 cases would be also sufficient to detect 10% difference in OS, the target number of cases was set as 600. However, the recruitment was very difficult. The Independent Data Monitoring Committee recommended us to transiently stop the recruitment at the end of August 2015 when the number of the registered cases reached 308. At submission of this abstract, we are considering whether the current number (308) is enough or not to detect 10% difference in RFS by calculating conditional predictive power. We will describe the trial design, and the current situations in detail for debate. Clinical trial information: UMIN:000001795.

Oral adjuvant chemotherapy using uracil-tegafur (UFT) with leucovorin (LV) after resection of colorectal cancer liver metastases: Long-term survival results of the phase III UFT/LV study

672

Background: Surgical resection has been accepted as the standard therapy for colorectal cancer liver metastases (CRLM), however, high recurrence incidence even after curative resection remains a severe problem. The 1st analysis of the UFT/LV trial showed that oral UFT/LV for 6 months significantly prolonged relapse-free survival (RFS) after resection for CRLM (Kobayashi A et al. ASCO 2014, Hasegawa K et al. PlosOne 2016 E-pub). To further evaluate the impact of the UFT/LV therapy on overall survival (OS), we performed the 2nd analysis under longer follow-up period, as have been scheduled by the protocol. Methods: Patients undergoing curative resection of CRLM were randomly assigned to either UFT/LV or surgery alone (control) group. In the UFT/LV group, 5 cycles of adjuvant UFT/LV (UFT 300mg/m2 and LV 75 mg/day for 28 days followed by 7 days rest in one cycle) were administered. Results: Between 2004 and 2010, a total of 180 patients were enrolled to this trial, among whom 3 patients were ineligible for analysis. Median follow-up of the 2nd analysis was 6 years. The 5y-OS rate in the UFT/LV group was 65.3%, which was slightly better than the control group (62.2%) without statistical significance. The hazard ratio for death in the UFT/LV relative to the control was 0.86 (95% confidence interval: 0.54-1.38, P = 0.54). The OS curves of the 2 groups were identical within 4 years after resection, however, the OS curve of the UFT/LV group seemed to go higher than the control group. The 5y-RFS rate in the UFT/LV group was 36.2%, which was significantly better than that in the control group (32.3%), as have been shown by the 1st analysis. Conclusions: The results of the 2nd analysis suggested that oral UFT/LV adjuvant chemotherapy might be also useful to prolong OS, as have been confirmed for RFS. This regimen can be recommended as an alternative choice after hepatic resection for CRLM. Clinical trial information: C000000013.

Liver resection for hepatocellular carcinoma associated with hepatic vein invasion: A Japanese nationwide survey

371

Background: Because of the rarity of hepatic vein tumor thrombus (HVTT), compared with portal vein tumor thrombus (PVTT), in patients with hepatocellular carcinoma (HCC), little is known about this disease entity. The aim of this study was to evaluate the prognosis of each treatment modality for HVTT through an analysis of data collected in a Japanese nationwide survey. Methods: We analyzed data for 1,021 Child-Pugh A HCC patients with HVTT without inferior vena cava invasion registered between 2000 and 2007. Of these patients, 540 patients who underwent liver resection (LR) and 481 patients who received other treatments were compared. The propensity scores were calculated and we successfully matched 244 patients (52.5% of the LR group). Results: The median survival time (MST) in the LR group was 2.89 years longer than that in the non-LR group (4.47 years vs 1.58 years; P < 0.001) and 1.17 years longer than that in the non-LR group (2.93 years vs 1.76 years; P = 0.009) in a propensity score-matched cohort. After curative resection, the MSTs were similar between patients with HVTT in the peripheral hepatic vein and those with HVTT in the major hepatic vein (4.85 years vs 4.67 years; P = 0.974). In the LR group, the postoperative 90-day mortality rate was 3.4% (16patients). In patients without PVTT, the MST was significantly better than that in patients with PVTT (5.67 years vs. 1.88 years; P < 0.001). Conclusions: LR is associated with a good prognosis in HCC patients with HVTT, especially in patients without PVTT.

Gait Performance Trajectories and Incident Disabling Dementia Among Community-Dwelling Older Japanese

OBJECTIVES

Initial gait speed is a good predictor of dementia in later life. This prospective study used repeated measures analysis to identify potential gait performance trajectory patterns and to determine whether gait performance trajectory patterns were associated with incident disabling dementia among community-dwelling older Japanese.

DESIGN

A prospective, observational, population-based follow-up study.

SETTING

Japan, 2002 to 2014.

PARTICIPANTS

A total of 1686 adults without dementia (mean [SD] age, 71.2 [5.6] years; women, 56.3%) aged 65 to 90 years participated in annual geriatric health assessments during the period from June 2002 through July 2014. The average number of follow-up assessments was 3.9, and the total number of observations was 6509.

MEASUREMENTS

Gait performance was assessed by measuring gait speed and step length at usual and maximum paces. A review of municipal databases in the Japanese public long-term care insurance system revealed that 196 (11.6%) participants developed disabling dementia through December 2014.

RESULTS

We identified 3 distinct trajectory patterns (high, middle, and low) in gait speed and step length at usual and maximum paces in adults aged 65 to 90 years; these trajectory patterns showed parallel declines among men and women. After adjusting for important confounders, participants in the low trajectory groups for gait speed and step length at usual pace were 3.46 (95% confidence interval 1.88-6.40) and 2.12 (1.29-3.49) times as likely to develop incident disabling dementia, respectively, as those in the high trajectory group. The respective values for low trajectories of gait speed and step length at maximum pace were 2.05 (1.02-4.14) and 2.80 (1.48-5.28), respectively.

CONCLUSIONS

Regardless of baseline level, the 3 major trajectory patterns for gait speed and step length tended to show similar age-related changes in men and women in later life. Individuals with low trajectories for gait speed and step length had a higher dementia risk, which highlights the importance of interventions for improvements in gait performance, even among older adults with low gait performance.

Survival benefit of liver resection for hepatocellular carcinoma associated with portal vein invasion

BACKGROUND & AIMS

The presence of portal vein tumor thrombosis (PVTT) in patients with hepatocellular carcinoma (HCC) is regarded as indicating an advanced stage, and liver resection (LR) is not recommended. The aim of this study was to evaluate the survival benefit of LR for HCC patients with PVTT through the analysis of the data from a Japanese nationwide survey.

METHODS

We analyzed data for 6474 HCC patients with PVTT registered between 2000 and 2007. Of these patients, 2093 patients who underwent LR and 4381 patients who received other treatments were compared. The propensity scores were calculated and we successfully matched 1058 patients (66.1% of the LR group).

RESULTS

In the Child-Pugh A patients, the median survival time (MST) in the LR group was 1.77years longer than that in the non-LR group (2.87years vs. 1.10years; p<0.001) and 0.88years longer than that in the non-LR group (2.45years vs. 1.57years; p<0.001) in a propensity score-matched cohort. A subgroup analysis revealed that LR provides a survival benefit regardless of age, etiology of HCC, tumor marker elevation, and tumor number. The survival benefit was not statistically significant only in patients with PVTT invading the main trunk or contralateral branch. In the LR group, the postoperative 90-day mortality rate was 3.7% (68 patients).

CONCLUSIONS

As long as the PVTT is limited to the first-order branch, LR is associated with a longer survival outcome than non-surgical treatment.

LAY SUMMARY

The presence of portal vein tumor thrombosis in patients with hepatocellular carcinoma is regarded as indicating an advanced stage, and liver resection is not recommended. We performed a multicenter, nationwide study to assess the survival benefit of liver resection in hepatocellular carcinoma patients with portal vein tumor thrombosis using propensity score-based matching. As long as the portal vein tumor thrombosis is limited to the first-order branch, liver resection is associated with a longer survival outcome than non-surgical treatment.

Randomized clinical trial comparing two vessel-sealing devices with crush clamping during liver transection

Background

Previous RCTs have failed to demonstrate the usefulness of combining energy devices with the conventional clamp crushing method to reduce blood loss during liver transection. Here, the combination of an ultrasonically activated device (UAD) and a bipolar vessel-sealing device (BVSD) with crush clamping was investigated.

Methods

Patients scheduled to undergo hepatectomy at the University of Tokyo Hospital or Nihon University Itabashi Hospital were eligible for this parallel-group, single-blinded randomized study. Patients were assigned to a control group (no energy device used), an UAD group or a BVSD group. The primary endpoint was the volume of blood loss during liver transection. Outcomes of the control group and the combined energy device groups (UAD plus BVSD) were first compared. Pairwise comparisons among the three groups were made for outcomes for which the combined energy device group was superior to the control group.

Results

A total of 380 patients were enrolled between July 2012 and May 2014; 116 patients in the control group, 122 in the UAD group and 123 in the BVSD group were included in the final analysis. Median blood loss during liver transection was lower in the combined energy device group (245 patients) than in the control group (116 patients): median 190 (range 0–3575) versus 230 (range 3–1570) ml (P = 0·048). Pairwise comparison revealed that blood loss was lower in the BVSD group than in the control group (P = 0·043).

Conclusion

The use of energy devices combined with crush clamping reduced blood loss during liver transection. Registration number: C000008372 (www.umin.ac.jp/ctr/index.htm).

Effect of Optimal Medical Therapy Before Procedures on Outcomes in Coronary Patients Treated With Drug-Eluting Stents

It has not been established whether the achievement of optimal medical therapy (OMT) before implantation of a drug-eluting stent has a clinical benefit for patients with stable coronary artery disease (CAD). This study included 3,004 patients with CAD treated with drug-eluting stent from 123 Japanese participating centers. The achievement of OMT was defined as control of blood pressure <130/80 mm Hg, hemoglobin A1c <7.0%, and low-density lipoprotein cholesterol <100 mg/dl. The primary end point was target vessel failure, a composite of death related to the target vessel, myocardial infarction, or clinically driven revascularization at 24 months after stent implantation. Immediately before the procedure, only 548 patients (18.2%) had achieved all 3 target criteria (the achieved OMT group), whereas the remaining 2,456 patients failed to achieve one or more criteria (the non-OMT group). At 24 months, the incidence of target vessel failure was 7.0% in the achieved OMT group versus 10.0% in the non-OMT group (hazard ratio 0.68, 95% CI 0.48 to 0.96, p = 0.03). The incidence of non-Q-wave myocardial infarction was also lower in the achieved OMT group than in the non-OMT group (0.5% vs 1.5%, p = 0.08). Multivariate logistic regression analysis identified that hemoglobin A1c <7.0% was the only protective predictor of 24-month target vessel failure (odds ratio 0.56, 95% CI 0.43 to 0.73, p <0.01). In conclusion, this study demonstrated that in patients with stable CAD scheduled for stent implantation, achievement of OMT before percutaneous coronary intervention significantly reduced subsequent cardiac events. Achievement of OMT is still insufficient in modern clinical practice.

Overlap coefficient for assessing the similarity of pharmacokinetic data between ethnically different populations

We developed a method to assess the similarity of pharmacokinetic data between ethnically different populations. An evaluation of confidence intervals for the mean difference in pharmacokinetic parameters, such as area under the concentration-versus-time curve (AUC), between populations is often used. We propose the use of the overlap coefficient (OC), which represents the proportion of overlap between two probability distributions, as a measure of the similarity between distributions. We considered five OC estimators – two parametric ones and three nonparametric ones. Simulation studies were conducted to compare the performance of the five OC estimators and their bootstrap confidence intervals. Results showed that nonparametric estimators with fixed-bandwidth kernel density estimation had a smaller mean squared error in almost all situations, and their coverage probabilities were close to the nominal level. The proposed method was applied to pharmacokinetic data from a bridging study of a combination therapy for metastatic colorectal cancer patients in the USA and Japan. From the analyses of this study, it was suggested that the distributions of the logarithmically transformed AUC for leucovorin and 5-fluorouracil were similar between the two populations.

Estimation of the average causal effect among subgroups defined by post-treatment variables

Background In clinical trials, when comparing treatments in a subgroup of patients defined by an event that occurred after randomization is required, the standard estimator that adjusts for the post-treatment variable does not have a causal interpretation.

Purpose To address this problem, we formulate clinically relevant causal estimands using the principal stratification framework developed by Frangakis and Rubin [3], and propose a new estimation method for the principal causal effect.

Methods We consider the comparison of the duration of response among patients who responded to chemotherapy in a cancer clinical trial. Our goal is to estimate the local average treatment effect, that is, the treatment difference among patients who would have responded to either treatment. In order to identify this estimand, we make the assumption that the value of the counterfactual indicator of response is independent of both the actual response status and the outcome variable of interest conditional on the covariates. The proposed estimator is a weighted average of the standard estimators for responders where weights are the probability that the response would have occurred had the patient received the other treatment.

Results The proposed method is applied to data from a randomized phase III clinical trial in patients with advanced non-small-cell lung cancer. The average difference for the duration of response among responders estimated by the proposed method and the standard one was 16.1 (days) and 9.5 (days), respectively. We also evaluate the performance of the proposed method through simulation studies, which showed that the proposed estimator was unbiased, while the standard one was largely biased.

Conclusions We have developed an estimation method for the local average treatment effect. For any type of outcome variables, our estimator can be easily constructed and can be interpreted as the treatment effect among patients who would have had the event in either treatment group.

Adjuvant Oral Uracil-Tegafur with Leucovorin for Colorectal Cancer Liver Metastases: A Randomized Controlled Trial

Background

The 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).

Methods

In 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).

Results

Between 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).

Conclusion

Adjuvant therapy with UFT/LV effectively prolongs RFS after hepatic resection for CLM and can be recommended as an alternative choice.

Trial Registration

UMIN Clinical Trials Registry C000000013

Survival Analysis over 28 Years of 173,378 Patients with Hepatocellular Carcinoma in Japan

BACKGROUND

Beginning in 1967, the Liver Cancer Study Group of Japan (LCSGJ) started a nationwide prospective registry of all patients with hepatocellular carcinoma (HCC) diagnosed at more than 700 institutions. To determine the effectiveness of surveillance and treatment methods longitudinally, we analyzed improvements over time in overall survival (OS) of 173,378 patients with HCC prospectively entered into the LCSGJ registry between 1978 and 2005.

METHODS

All patients from more than 700 institutions throughout Japan with HCC were entered into the LCSGJ registry. Patients were grouped by years of diagnosis, with OS and 5-year OS rates being calculated. We also assessed OS and 5-year OS rates in patients who underwent resection, local ablation, transarterial chemoembolization (TACE), and hepatic arterial infusion chemotherapy (HAIC) and in those with baseline serum alpha-fetoprotein (AFP) levels ≥400 ng/ml.

RESULTS

The 5- and 10-year OS rates in the cohort of 173,378 patients were 37.9% and 16.5%, respectively. However, over time, the mean maximum tumor size decreased significantly, whereas 5-year OS rates and median survival time increased significantly. Similar findings were observed separately in patients who underwent resection, local ablation, TACE, and HAIC, as well as in patients with AFP levels ≥400 ng/ml.

CONCLUSION

The establishment of a nationwide HCC surveillance program in Japan has contributed to longer median OS and increased OS rates in patients diagnosed with this disease. These findings suggest that the establishment of a surveillance program in other countries with patients at risk for HCC may provide significant survival benefits.

Survival Benefit of Locoregional Treatment for Hepatocellular Carcinoma with Advanced Liver Cirrhosis

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) with decompensated liver cirrhosis (LC) is a life-threatening condition, which is amenable to liver transplantation (LT) as the standard first-line treatment. However, the application of LT can be limited due to a shortage of donor livers. This study aimed to clarify the effect of non-surgical therapy on the survival of patients with HCC and decompensated LC.

METHODS

Of the 58,886 patients with HCC registered in the nationwide survey of the Liver Cancer Study Group of Japan (January 2000-December 2005), we included 1,344 patients with primary HCC and Child-Pugh (C-P) grade C for analysis in this retrospective study. Among the patients analyzed, 108 underwent LT, 273 were treated by local ablation therapy (LAT), 370 were treated by transarterial chemoembolization (TACE), and 593 received best supportive care (BSC). The effect of LT, LAT, and TACE on overall survival (OS) was analyzed using multivariate and propensity score analyses.

RESULTS

Patient characteristics did not differ significantly between each treatment group and the BSC group, after propensity score matching. LAT (hazard ratio [HR]) =0.568; 95% confidence interval [CI], 0.40-0.80) and TACE (HR=0.691; 95% CI, 0.50-0.96) were identified as significant contributors to OS if the C-P score was less than 11 and tumor conditions met the Milan criteria.

CONCLUSIONS

For patients with HCC within the Milan criteria and with a C-P score of 10 or 11, locoregional treatment can be used as a salvage treatment if LT is not feasible.