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Biomedical subjects

Sally Hunsberger

Publications and source records attributed to Sally Hunsberger.

10 recordsLinked to original sources
PubMed2006

Very high-dose methotrexate (33.6 g/m(2)) as central nervous system preventive therapy for childhood acute lymphoblastic leukemia: results of National Cancer Institute/Children's Cancer Group trials CCG-191P, CCG-134P and CCG-144P.

Between 1977 and 1991, the Children's Cancer Group and the National Cancer Institute conducted three trials of very high-dose methotrexate (33.6 g/m2; VHD-MTX) in place of cranial radiation (CRT) as central nervous system (CNS) preventive therapy, and assessed efficacy, acute toxicity and long-term neurocognitive outcome. CCG-191P compared VHD-MTX to CRT plus intrathecal methotrexate (IT-MTX) in 181 patients and demonstrated equivalent survival. However, patients treated with CRT had poorer performance on neurocognitive testing over time. CCG-134P evaluated the addition of intensified systemic and intrathecal therapy to VHD-MTX in 128 patients with high-risk acute lymphoblastic leukemia (ALL) and demonstrated reduced CNS relapse compared to the CCG-191P trial, but equivalent survival. CCG-144P compared VHD-MTX to IT-MTX alone in 175 patients with average-risk ALL and demonstrated equivalent survival. VHD-MTX was associated with significant toxicities, particularly neutropenia, transient hepatic dysfunction and sepsis. VHD-MTX achieved similar survival to other CNS-directed therapies without the long-term impact on intelligence, but with substantial acute toxicities.

Adolescent↗
PubMed2005

Design issues of randomized phase II trials and a proposal for phase II screening trials.

Future progress in improving cancer therapy can be expedited by better prioritization of new treatments for phase III evaluation. Historically, phase II trials have been key components in the prioritization process. There has been a long-standing interest in using phase II trials with randomization against a standard-treatment control arm or an additional experimental arm to provide greater assurance than afforded by comparison to historic controls that the new agent or regimen is promising and warrants further evaluation. Relevant trial designs that have been developed and utilized include phase II selection designs, randomized phase II designs that include a reference standard-treatment control arm, and phase II/III designs. We present our own explorations into the possibilities of developing "phase II screening trials," in which preliminary and nondefinitive randomized comparisons of experimental regimens to standard treatments are made (preferably using an intermediate end point) by carefully adjusting the false-positive error rates (alpha or type I error) and false-negative error rates (beta or type II error), so that the targeted treatment benefit may be appropriate while the sample size remains restricted. If the ability to conduct a definitive phase III trial can be protected, and if investigators feel that by judicious choice of false-positive probability and false-negative probability and magnitude of targeted treatment effect they can appropriately balance the conflicting demands of screening out useless regimens versus reliably detecting useful ones, the phase II screening trial design may be appropriate to apply.

Clinical Trials, Phase II as Topic↗
PubMed2005

Dose escalation trial designs based on a molecularly targeted endpoint.

Traditional phase I dose-finding studies for chemotoxic agents base dose escalation on toxicity, with escalation continuing until unacceptable toxicity is observed. Recent development of molecularly targeted agents that have little or no toxicity in the therapeutic dose range has raised questions over the best study designs for phase I studies. Two types of designs are proposed and evaluated in this paper. In these designs, escalation is based on a binary response that indicates whether or not the agent has had the desired effect on the molecular target. One design is developed to ensure that if the true target response rate is low there will be a high probability of escalating and if the true target response rate is high there will be a low probability of escalating. The other design is developed to continue to escalate as long as the true response rate is increasing and to stop escalating when the response rate plateaus or decreases. A limited simulation study is performed and the designs are compared with respect to the dose level at the end of escalation and the number of patients treated on study.

Clinical Trials, Phase I as Topic↗
PubMed2005

Preliminary data release for randomized clinical trials of noninferiority: a new proposal.

Noninferiority trials often require a long follow-up period for the data to reach the maturity needed for definitive analysis. A proposal is presented that allows for early release of outcome data from a carefully specified subset of noninferiority trials. This subset is defined so that the early release of the data will be potentially useful to patients who face a treatment decision but will not compromise the integrity of the trial or interfere with the completion of the trial to its definitive analysis. In particular, the release of the data will only occur after the last participant has been randomly assigned and is off treatment-arm-specific therapy and only if it is unlikely that subsequent treatment and/or follow-up practices will change based on the knowledge of released data. In contrast to standard interim monitoring, (1) the release of the data would be automatic and independent of the observed data, and (2) the trial would continue on to its planned final analysis and not be stopped. Examples are given demonstrating how the proposal would work, along with a discussion of possible objections to the proposal.

Clinical Trials Data Monitoring Committees↗
PubMed2005

On analyzing circadian rhythms data using nonlinear mixed models with harmonic terms.

Wang, Ke, and Brown (2003, Biometrics59, 804-812) developed a smoothing-based approach for modeling circadian rhythms with random effects. Their approach is flexible in that fixed and random covariates can affect both the amplitude and phase shift of a nonparametrically smoothed periodic function. In motivating their approach, Wang et al. stated that a simple sinusoidal function is too restrictive. In addition, they stated that "although adding harmonics can improve the fit, it is difficult to decide how many harmonics to include in the model, and the results are difficult to interpret." We disagree with the notion that harmonic models cannot be a useful tool in modeling longitudinal circadian rhythm data. In this note, we show how nonlinear mixed models with harmonic terms allow for a simple and flexible alternative to Wang et al.'s approach. We show how to choose the number of harmonics using penalized likelihood to flexibly model circadian rhythms and to estimate the effect of covariates on the rhythms. We fit harmonic models to the cortisol circadian rhythm data presented by Wang et al. to illustrate our approach. Furthermore, we evaluate the properties of our procedure with a small simulation study. The proposed parametric approach provides an alternative to Wang et al.'s semiparametric approach and has the added advantage of being easy to implement in most statistical software packages.

Circadian Rhythm↗
PubMed2003

Practical midcourse sample size modification in clinical trials.

Power calculations are very important in the planning of a well-designed clinical trial. Sometimes there is limited information available before the trial, making it highly desirable to adjust the sample size after seeing actual trial data. Indeed, there has been a recent proliferation of papers promising great flexibility in midcourse correction of sample size and other design features, such as choice of primary endpoint. We point out the difficulty in accurately estimating the treatment effect midway through a trial, and we encourage the use of a simple, conservative approach whereby sample size can be increased but not decreased from what was originally planned. We show how to compute the p value and confidence interval for this two-stage procedure. If the original sample size is maintained, analysis of the data is the same as for a fixed sample procedure.

Bayes Theorem↗
PubMed2003

The effect of digoxin on the quality of life in patients with heart failure.

BACKGROUND: The Digitalis Investigation Group (DIG) trial was a randomized double-blind placebo-controlled study that examined the effect of digoxin on mortality in 7,788 patients with heart failure and sinus rhythm. A prespecified substudy evaluated the effect of digoxin therapy on health-related quality of life (HQOL) in a subset of these patients. METHODS: Patients in the DIG trial had clinical heart failure and were randomized to either digoxin or placebo in addition to their baseline diuretic and angiotensin-converting enzyme therapy (n = 7,788). The patients in this substudy had HQOL measured using a self-administered questionnaire employing scales that measured general health, physical functioning, depression, anger, anxiety, life satisfaction, and disease specific measures. A subjective assessment by the investigator and a 6-minute walk test evaluated functional status. HQOL was measured at baseline and at the 4- and 12-month follow-up visits. RESULTS: The baseline characteristics of the patients in the quality of life substudy (n = 589) were comparable to the remaining patients in the study (n = 7,199) by age and other clinical measures, including history of prior myocardial infarction or etiology of heart failure; heart failure was of shorter duration and the ejection fraction was slightly better than in the main trial. Within the substudy, patients receiving digoxin (n = 298) or placebo (n = 291) were also similar in baseline characteristics. There was no statistically significant difference in any HQOL measure between the digoxin and the placebo groups at baseline. At the 4-month visit, only perceived health was improved in the digoxin group. At 12 months, there was no statistically significant difference in perceived health, physical functioning, Minnesota Living with Heart Failure, depression, anxiety, anger, Ladder of Life, or the 6-minute walk between the digoxin and placebo groups. CONCLUSION: In this subset of the DIG population, digoxin therapy had no effect on the HQOL in patients with heart failure in sinus rhythm.

Aged↗
PubMed2002

Innovative designs in behavioural trials.

Clinical trials that compare pharmacological and behavioural treatments require extra attention to design on the part of the investigators. Many of the standard control mechanisms for comparison of active drug to placebo and behavioural therapy to control therapy create problems when the two types of interventions are combined. The most important of these problems is the introduction of non-specific effects introduced by behavioural therapists and physicians that can bias the study. Solutions to these problems require procedures that are common to both types of studies and the introduction of more complex statistical designs to adequately control the proposed comparisons. It may also be necessary to have a robust statistical method to address informative censoring since patients assigned to behavioural therapy may drop out of the study for different reasons than patients who drop out of a pharmacological trial. In this paper we use the design of the Raynaud's Treatment Study to demonstrate methods that can be used to control for non-specific effects and differential drop-out from the study.

Behavior↗
PubMed2002

Parametric and semiparametric approaches to testing for seasonal trend in serial count data.

We present two tests for seasonal trend in monthly incidence data. The first approach uses a penalized likelihood to choose the number of harmonic terms to include in a parametric harmonic model (which includes time trends and autogression as well as seasonal harmonic terms) and then tests for seasonality using a parametric bootstrap test. The second approach uses a semiparametric regression model to test for seasonal trend. In the semiparametric model, the seasonal pattern is modeled nonparametrically, parametric terms are included for autoregressive effects and a linear time trend, and a parametric bootstrap test is used to test for seasonality. For both procedures, a null distribution is generated under a null Poisson model with time trends and autoregression parameters. We apply the methods to skin melanoma incidence rates collected by the surveillance, epidemiology, and end results (SEER) program of the National Cancer Institute, and perform simulation studies to evaluate the type I error rate and power for the two procedures. These simulations suggest that both procedures are alpha-level procedures. In addition, the harmonic model/bootstrap test had similar or larger power than the semiparametric model/bootstrap test for a wide range of alternatives, and the harmonic model/bootstrap test is much easier to implement. Thus, we recommend the harmonic model/bootstrap test for the analysis of seasonal incidence data.

Journal Article↗