Randomization-based adjustment of multiple treatment hazard ratios for covariates with missing data.

Clinical trials are designed to compare treatment effects when applied to samples from the same population. Randomization is used so that the samples are not biased with respect to baseline covariates that may influence the efficacy of the treatment. We develop randomization-based covariance adjustment methodology to estimate the log hazard ratios and their confidence intervals of multiple treatments in a randomized clinical trial with time-to-event outcomes and missingness among the baseline covariates. The randomization-based covariance adjustment method is a computationally straight-forward method for handling missing baseline covariate values.

Nonparametric randomization-based covariate adjustment for stratified analysis of time-to-event or dichotomous outcomes.

Time-to-event or dichotomous outcomes in randomized clinical trials often have analyses using the Cox proportional hazards model or conditional logistic regression, respectively, to obtain covariate-adjusted log hazard (or odds) ratios. Nonparametric Randomization-Based Analysis of Covariance (NPANCOVA) can be applied to unadjusted log hazard (or odds) ratios estimated from a model containing treatment as the only explanatory variable. These adjusted estimates are stratified population-averaged treatment effects and only require a valid randomization to the two treatment groups and avoid key modeling assumptions (e.g., proportional hazards in the case of a Cox model) for the adjustment variables. The methodology has application in the regulatory environment where such assumptions cannot be verified a priori. Application of the methodology is illustrated through three examples on real data from two randomized trials.

A multistage analysis strategy for a clinical trial to assess successively more stringent criteria for a primary endpoint with a low event rate.

This paper describes how a multistage analysis strategy for a clinical trial can assess a sequence of hypotheses that pertain to successively more stringent criteria for excess risk exclusion or superiority for a primary endpoint with a low event rate. The criteria for assessment can correspond to excess risk of an adverse event or to a guideline for sufficient efficacy as in the case of vaccine trials. The proposed strategy is implemented through a set of interim analyses, and success for one or more of the less stringent criteria at an interim analysis can be the basis for a regulatory submission, whereas the clinical trial continues to accumulate information to address the more stringent, but not futile, criteria. Simulations show that the proposed strategy is satisfactory for control of type I error, sufficient power, and potential success at interim analyses when the true relative risk is more favorable than assumed for the planned sample size.

Design and analysis of stepped wedge cluster randomized trials.

Cluster randomized trials (CRT) are often used to evaluate therapies or interventions in situations where individual randomization is not possible or not desirable for logistic, financial or ethical reasons. While a significant and rapidly growing body of literature exists on CRTs utilizing a "parallel" design (i.e. I clusters randomized to each treatment), only a few examples of CRTs using crossover designs have been described. In this article we discuss the design and analysis of a particular type of crossover CRT - the stepped wedge - and provide an example of its use.

Reproducibility of blood pressure dipping: relation to day-to-day variability in sleep quality.

Previous studies of the reproducibility of blood pressure (BP) dipping have yielded inconsistent results. Few have examined factors that may influence day-to-day differences in dipping. Ambulatory BP monitoring was performed on three occasions, approximately 1 week apart, in 115 untreated adult subjects with elevated clinic BPs. The mean ± standard deviation BP dip was 18 ± 7/15 ± 5 mm Hg (sleep/awake BP ratio = 0.87 ± 0.05/0.82 ± 0.06), with a median (interquartile range) day-to-day variation of 5.2 (3.1-8.1)/4.3 (2.8-5.6) mm Hg. There was no decrease in variability with successive measurements. The reproducibility coefficient (5.6 [95% confidence interval, 5.1-6.1] mm Hg) was greater and the intraclass correlation coefficient (0.53 [95% confidence interval, 0.42-0.63]) was smaller for the systolic dip than for 24-hour or awake systolic BPs, suggesting greater day-to-day variability in dipping. Variability in systolic dipping was greater in subjects with higher awake BP, but was not related to age, gender, race, or body mass index. Within individuals, day-to-day variations in dipping were related to variations in the fragmentation index (P < .001), a measure of sleep quality. Although mean 24-hour and awake BPs were relatively stable over repeated monitoring days, our study confirms substantial variability in BP dipping. Day-to-day differences in dipping are related to sleep quality.

Recombinant factor VIIa analog NN1731 (V158D/E296V/M298Q-FVIIa) enhances fibrin formation, structure and stability in lipidated hemophilic plasma.

INTRODUCTION: The bypassing agent recombinant factor VIIa (rFVIIa) is efficacious in treating bleeding in hemophilia patients with inhibitors. Efforts have focused on the rational engineering of rFVIIa variants with increased hemostatic potential. One rFVIIa analog (V158D/E296V/M298Q-FVIIa, NN1731) improves thrombin generation and clotting in purified systems, whole blood from hemophilic patients and factor VIII-deficient mice. METHODS: We used calibrated automated thrombography and plasma clotting assays to compare effects of bypassing agents (rFVIIa, NN1731) on hemophilic clot formation, structure, and ability to resist fibrinolysis. RESULTS: Both rFVIIa and NN1731 shortened the clotting onset and increased the maximum rate of fibrin formation and fibrin network density in hemophilic plasma clots. In the presence of tissue plasminogen activator, both rFVIIa and NN1731 shortened the time to peak turbidity (TTPeak(tPA)) and increased the area under the clot formation curve (AUC(tPA)). Phospholipids increased both rFVIIa and NN1731 activity in a lipid concentration-dependent manner. Estimated geometric mean concentrations of rFVIIa and NN1731 producing similar onset, rate, TTPeak(tPA), and AUC(tPA) as seen with 100% factors VIII and IX were: 24.5, 74.3, 29.7, and 37.1 nM rFVIIa, and 8.6, 31.2, 9.0, and 11.3 nM NN1731, respectively. In each case, the NN1731 concentration was significantly lower than rFVIIa. CONCLUSIONS: These findings suggest that like rFVIIa, NN1731 improves the formation, structure, and stability of hemophilic clots. Higher lipid concentrations may facilitate assessment of both rFVIIa and NN1731 activity. NN1731 appears likely to support rapid clot formation in tissues with high endogenous fibrinolytic activity.

Colorectal Chemoprevention Pilot Study (SWOG-9041), randomized and placebo controlled: the importance of multiple luminal lesions.

BACKGROUND: Colorectal cancer is common worldwide and chemoprevention has the potential of reducing the number of individuals who may suffer and perish from this disease. METHODS: A randomized placebo controlled pilot study in colorectal cancer patients was performed using calcium carbonate as the test agent in a multi-institutional oncology study group. RESULTS: Two hundred twenty volunteers were randomized in the study. The primary goals of compliance, accrual, and toxicity monitoring are presented. Presence of multiple adenomas at study entry and subsequent development of metachronous adenomas were recorded and found to be associated with synchronous adenomas. The secondary endpoint of recurrent adenomas indicated lower rates of new adenoma in the volunteers randomized to the calcium group. CONCLUSION: This pilot study indicates the feasibility of enrolling survivors of colorectal cancer as study volunteers in a colorectal neoplasm chemoprevention clinical trial and oral calcium continues to be a potentially effective drug in reducing colorectal adenomas.

Late cardiac effects of adjuvant chemotherapy in breast cancer survivors treated on Southwest Oncology Group protocol s8897.

PURPOSE: The late cardiac effects of adjuvant anthracycline therapy in survivors of early-stage breast cancer have had limited study. Subclinical and clinical cardiac late effects may contribute to added comorbidity over time. PATIENTS AND METHODS: We recruited patients treated on Southwest Oncology Group (SWOG) protocol S8897 who had been randomly assigned to adjuvant chemotherapy with or without doxorubicin. Left ventricular ejection fraction (LVEF) was evaluated at 5 to 8 years and 10 to 13 years after treatment randomization. Cardiac risk factors and events were reported by clinicians annually between the two assessments. RESULTS: A total of 180 breast cancer survivors from a potential sample of 1,176 patients were entered, 163 patients at 5 to 8 years and 17 additional patients at 10 to 13 years, with 93 longitudinal assessments of LVEF. There was no significant difference in the proportion of women with an LVEF less than 50% at 5 to 8 (cyclophosphamide, doxorubicin, and fluorouracil [CAF] v cyclophosphamide, methotrexate, and fluorouracil [CMF]: 5% v 7%; P = .68) or 10 to 13 years (CAF v CMF: 3% v 0%; P = .16); however, in an exploratory analysis, the mean LVEF in the doxorubicin group was statistically significantly lower in the 5- to 8-year sample (64.8% v 61.4%; P = .01) but not in the 10- to 13-year sample. In the longitudinal analysis, there was no significant deterioration in LVEF. CONCLUSION: Women enrolled onto an adjuvant chemotherapy treatment clinical trial for breast cancer were successfully recruited to participate in a research study of the late effects of treatment, although many SWOG institutions and potentially eligible patients chose not to participate. In this selected sample, with up to 13 years of follow-up, exposure to doxorubicin did not increase the likelihood of adverse cardiac effects.

Predominant treatment failure in postprostatectomy patients is local: analysis of patterns of treatment failure in SWOG 8794.

PURPOSE: Southwest Oncology Group (SWOG) trial 8794 demonstrated that adjuvant radiation reduces the risk of biochemical (prostate-specific antigen [PSA]) treatment failure by 50% over radical prostatectomy alone. In this analysis, we stratified patients as to their preradiation PSA levels and correlated it with outcomes such as PSA treatment failure, local recurrence, and distant failure, to serve as guidelines for future research. PATIENTS AND METHODS: Four hundred thirty-one subjects with pathologically advanced prostate cancer (extraprostatic extension, positive surgical margins, or seminal vesicle invasion) were randomly assigned to adjuvant radiotherapy or observation. RESULTS: Three hundred seventy-four eligible patients had immediate postprostatectomy and follow-up PSA data. Median follow-up was 10.2 years. For patients with a postsurgical PSA of 0.2 ng/mL, radiation was associated with reductions in the 10-year risk of biochemical treatment failure (72% to 42%), local failures (20% to 7%), and distant failures (12% to 4%). For patients with a postsurgical PSA between higher than 0.2 and