Biomedical subjects

KyungMann Kim

Publications and source records attributed to KyungMann Kim.

10 recordsLinked to original sources

PubMed2007

Latent-variable models for longitudinal data with bivariate ordinal outcomes.

We use the concept of latent variables to derive the joint distribution of bivariate ordinal outcomes, and then extend the model to allow for longitudinal data. Specifically, we relate the observed ordinal outcomes using threshold values to a bivariate latent variable, which is then modelled as a linear mixed model. Random effects terms are used to tie all together repeated observations from the same subject. The cross-sectional association between the two outcomes is modelled through the correlation coefficient of the bivariate latent variable, conditional on random effects. Assuming conditional independence given random effects, the marginal likelihood, under the missing data at random assumption, is approximated using an adaptive Gaussian quadrature for numerical integration. The model provides fixed effects parameters that are subject-specific, but retain the population-averaged interpretation when properly scaled. This is particularly well suited for the situation in which population comparisons and individual level contrasts are of equal importance. Data from a psychiatric trial, the Fluvoxamine (an antidepressant drug) study, are used to illustrate the methodology.

Antidepressive Agents, Second-Generation↗

PubMed2006

Celecoxib for the prevention of sporadic colorectal adenomas.

BACKGROUND: Studies showing that drugs that inhibit cyclooxygenase-2 (COX-2) reduce the number of colorectal adenomas in animals and patients with familial adenomatous polyposis suggest that COX-2 inhibitors may also prevent sporadic colorectal neoplasia. METHODS: We randomly assigned patients who had adenomas removed before study entry to receive placebo (679 patients) or 200 mg (685 patients) or 400 mg (671 patients) of celecoxib twice daily. Randomization was stratified for the use of low-dose aspirin. Follow-up colonoscopies were performed at one and three years after randomization. The occurrence of newly detected colorectal adenomas was compared among the groups with the life-table extension of the Mantel-Haenszel test. RESULTS: Follow-up colonoscopies were completed at year 1 in 89.5 percent of randomized patients, and at year 3 in 75.7 percent. The estimated cumulative incidence of the detection of one or more adenomas by year 3 was 60.7 percent for patients receiving placebo, as compared with 43.2 percent for those receiving 200 mg of celecoxib twice a day (risk ratio, 0.67; 95 percent confidence interval, 0.59 to 0.77; P<0.001) and 37.5 percent for those receiving 400 mg of celecoxib twice a day (risk ratio, 0.55; 95 percent confidence interval, 0.48 to 0.64; P<0.001). Serious adverse events occurred in 18.8 percent of patients in the placebo group, as compared with 20.4 percent of those in the low-dose celecoxib group (risk ratio, 1.1; 95 percent confidence interval, 0.9 to 1.3; P=0.5) and 23.0 percent of those in the high-dose group (risk ratio, 1.2; 95 percent confidence interval, 1.0 to 1.5; P=0.06). As compared with placebo, celecoxib was associated with an increased risk of cardiovascular events (risk ratio for the low dose, 2.6; 95 percent confidence interval, 1.1 to 6.1; and risk ratio for the high dose, 3.4; 95 percent confidence interval, 1.5 to 7.9). CONCLUSIONS: These findings indicate that celecoxib is an effective agent for the prevention of colorectal adenomas but, because of potential cardiovascular events, cannot be routinely recommended for this indication. (ClinicalTrials.gov number, NCT00005094 [ClinicalTrials.gov].).

Adenoma↗

PubMed2006

Guidelines for data and safety monitoring for clinical trials not requiring traditional data monitoring committees.

This is a commissioned report by a writing committee formed by the Society for Clinical Trials. The committee was formed with the objectives of 1) reviewing data monitoring guidelines for confirmatory (phase III) trials published by the National Institutes of Health, US Food and Drug Administration, Veterans Administration, and the International Conference on Harmonisation and 2) proposing corresponding guidelines for exploratory clinical trials (ie, most phase I and phase II trials and others not requiring a fully independent data monitoring committee). These trials typically involve fewer subjects and are of shorter duration than phase III trials. Nevertheless there are safety concerns, especially because these are often the first human trials for a new intervention. Recommendations are given for appropriate elements of a data monitoring plan, decision criteria for institution of a data monitoring committee (DMC), and critical elements for a DMC to consider in exploratory trials. Review and approval of data monitoring plans are suggested to fall under Institutional Review Board purview. Forming a committee with all the characteristics of a traditional phase III trial monitoring committee may be warranted for a small fraction of exploratory trials. Such a panel could consist of both trial investigators and outside members. The paper concludes with examples of data and safety monitoring practice from the University of Wisconsin Comprehensive Cancer Center and the AIDS Clinical Trials Groups.

Acquired Immunodeficiency Syndrome↗

PubMed2005

Phase II trial of weekly paclitaxel in patients with advanced melanoma.

New therapies are needed to improve the prognosis of patients with metastatic melanoma. This study evaluates the safety and efficacy of weekly paclitaxel in patients with metastatic melanoma. Patients received paclitaxel at 80 mg/m over 1 h, weekly for 3 weeks, followed by a 1-week rest period. Disease status was assessed every other cycle. Treatment was continued until patients experienced either disease progression or unacceptable toxicity. Twenty-seven patients were enrolled in this phase II clinical trial. Of these patients, two were subsequently determined to be ineligible. All patients, however, were considered to be evaluable for toxicity and all patients were included for response assessment in an intention-to-treat analysis. Patients received paclitaxel for a median of two cycles (range, <1-8). None of the 27 patients showed a response to treatment. Eight patients had stable disease. The median progression-free survival was 1.8 months (95% confidence interval, 1.7-2.5 months) and the median survival was 7.6 months (95% confidence interval, 4.7-9.7 months). The most common grade 3 toxicity was neutropenia (four patients) and one patient had grade 4 neutropenia. Other treatment-related grade 3 toxicities included hypersensitivity reaction (one patient) and diarrhoea (one patient). Of note, five patients had peripheral neuropathy; however, in each case, the neuropathy was only grade 1. Weekly paclitaxel is relatively well tolerated and can maintain disease stability for some metastatic melanoma patients. Unfortunately, the anti-tumour activity of this single-agent therapy is low and additional treatment innovations are needed.

Adult↗

PubMed2004

Phase I clinical trial of the immunocytokine EMD 273063 in melanoma patients.

PURPOSE: To evaluate the safety, toxicity, in vivo immunologic activation, and maximum-tolerated dose (MTD) of EMD 273063 (hu14.18-IL-2) in patients with metastatic melanoma. PATIENTS AND METHODS: Thirty-three patients were treated with EMD 273063, a humanized anti-GD2 monoclonal antibody (mAb) linked to interleukin-2 (IL-2). EMD 273063 was given as a 4-hour intravenous infusion on days 1, 2, and 3 of week 1. Patients with stabilization or regression of disease could receive a second course of treatment at week 5. Dose levels evaluated were 0.8, 1.6, 3.2, 4.8, 6.0, and 7.5 mg/m2/d. RESULTS: Nineteen of 33 patients completed course 1 with stable disease and went on to receive course 2. Eight patients had stable disease on completion of course 2. Grade 3 adverse events included hypophosphatemia (11 patients), hyperglycemia (three patients), hypotension (two patients), thrombocytopenia (one patient), hypoxia (three patients), elevated hepatic transaminases (two patients), and hyperbilirubinemia (one patient). Opioids were required for treatment-associated arthralgias and/or myalgias during 17 of 52 treatment courses. No grade 4 adverse events were observed. Dose-limiting toxicities at the MTD included hypoxia, hypotension, and elevations in AST/ALT. Grade 3 toxicities were anticipated based on prior studies of IL-2 or anti-GD2 mAbs, and all resolved. Immune activation was induced, as measured by lymphocytosis, increased peripheral-blood natural killer activity, and cell numbers, and increased serum levels of the soluble alpha chain of the IL-2 receptor complex. CONCLUSION: Treatment with the immunocytokine EMD 273063 induced immune activation and was associated with reversible clinical toxicities at the MTD of 7.5 mg/m2/d in melanoma patients.

Adult↗

PubMed2004

Chemotherapy with or without radiotherapy in limited-stage diffuse aggressive non-Hodgkin's lymphoma: Eastern Cooperative Oncology Group study 1484.

PURPOSE: To compare low-dose (30 Gy) radiotherapy (RT) with observation (OBS) in limited-stage aggressive lymphoma patients achieving complete remission (CR) after chemotherapy, and to measure conversion from partial response (PR) to CR with high-dose (40 Gy) RT. PATIENTS AND METHODS: From 1984 to 1992, stage I (with risk factors) and II adults with diffuse aggressive lymphoma in CR after eight cycles of cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) were randomly assigned to 30 Gy involved-field RT or OBS. PR patients received 40 Gy RT. RESULTS: Among 172 CR patients, the 6-year disease-free survival (DFS) was 73% for low-dose RT versus 56% for OBS (two-sided P = .05). Failure-free survival (two-sided P = .06), and time to progression (two-sided P = .06) also favored RT. Intent-to-treat analyses yielded similar results. No survival differences were observed. Three RT versus 15 OBS patients relapsed in initial disease sites. At 6 years, failure-free survival was 63% in PR patients; conversion to CR did not significantly influence clinical outcome. CONCLUSION: For patients in CR after CHOP, low-dose RT prolonged DFS and provided local control, but no survival benefit was observed. The majority of PR patients were event-free at 6 years despite residual radiographic abnormalities. Future efforts should be directed toward improved imaging and more effective systemic therapies.

Adult↗

PubMed2004

Admissible two-stage designs for phase II cancer clinical trials.

In a typical two-stage design for a phase II cancer clinical trial for efficacy screening of cytotoxic agents, a fixed number of patients are initially enrolled and treated. The trial may be terminated for lack of efficacy if the observed number of tumour responses after the first stage is too small, thus avoiding treatment of patient with inefficacious regimen. Otherwise, an additional fixed number of patients are enrolled and treated to accumulate additional information on efficacy as well as safety. The minimax and the so-called 'optimal' designs by Simon have been widely used, and other designs have largely been ignored in the past for such two-stage cancer clinical trials. Recently Jung et al. proposed a graphical method to search for compromise designs with features more favourable than either the minimax or the optimal design. In this paper, we develop a family of two-stage designs that are admissible according to a Bayesian decision-theoretic criterion based on an ethically justifiable loss function. We show that the admissible designs include as special cases the Simon's minimax and the optimal designs as well as the compromise designs introduced by Jung et al. We also present a Java program to search for admissible designs that are compromises between the minimax and the optimal designs.

Bayes Theorem↗

PubMed2004

A Phase II trial of flavopiridol (NSC #649890) in patients with previously untreated metastatic androgen-independent prostate cancer.

PURPOSE: Flavopiridol is a cyclin-dependent kinase inhibitor with preclinical activity against prostate cancer cell lines. A Phase II trial was conducted to determine the activity of flavopiridol in patients with metastatic hormone-refractory prostate cancer. EXPERIMENTAL DESIGN: A total of 36 patients was enrolled from several institutions and treated with a 72-h continuous infusion of flavopiridol every 14 days at the eventual starting dose of 40 mg/m(2)/day. Dose escalation up to 60 mg/m(2)/day was permitted if no significant toxicity was observed. Responses were assessed every 12 weeks. Only those patients completing four courses of the 72-h infusion were considered evaluable for response because the primary objective was to determine progression-free survival at 6 months given the cytostatic nature of the agent. RESULTS: This study was conducted in a two-stage fashion. During the first stage, at least 20 evaluable patients needed to be enrolled to assess response. There were 22 of 36 patients evaluable for response. No objective responses were observed. Only 4 patients had stable disease for 16, 26, 29, and 48 weeks, respectively, stopping the trial by design as only 3 of 22 (14%) of the patients met the 6-month progression-free survival end point. The most common toxicities were diarrhea (grade 1 and 2) and nausea, although some grade 3 and 4 diarrhea (11 and 6%, respectively) were evident. CONCLUSIONS: Flavopiridol has disappointing single-agent activity in hormone-refractory prostate cancer when administered at this dose and schedule. Its use in prostate cancer should be reserved for evaluation in combination therapies or alternative schedules.

Aged↗

PubMed2003

Phase II study of second-line gemcitabine in sensitive or refractory small cell lung cancer.

UNLABELLED: Small cell lung cancer (SCLC) is highly sensitive to chemotherapy. Despite a dramatic initial response, however, most patients relapse. Given the activity of gemcitabine in non-small cell lung cancer (NSCLC), and early clinical trials suggesting activity of gemcitabine in chemo-naive SCLC patients, we conducted a phase II study to determine the efficacy and toxicities of gemcitabine in SCLC patients who have failed first-line chemotherapy. Gemcitabine 1250 mg/m(2) was given intravenously on days 1 and 8, every 3 weeks. Eligibility criteria included prior treatment with only one chemotherapy regimen and Eastern Cooperative Oncology Group (ECOG) performance status of 0-2. Patients with brain metastases were eligible. RESULTS: Between April 1998 and October 2001, 27 patients were enrolled: 15 patients with sensitive (S) disease (recurred>3 months after first-line chemotherapy) and 12 patients with refractory (R) disease (failed<3 months after first-line chemotherapy). Median age was 61 (range 45-74). All patients had received prior platinum-based therapy involving etoposide and either cisplatin or carboplatin. There were one early death and two early withdrawals because of toxicity. No responses were observed. Of 24 patients who received at least two cycles of gemcitabine, only three achieved stable disease after six cycles while 21 progressed. The median time to progression (TTP) was 6 weeks in S group, 5.6 weeks in R group, and 6 weeks overall. After a minimum potential follow-up of almost 1 year for all patients, the median survival was 8.8 months in S group, 4.2 months in R group, and 6.4 months for the whole group. One-year survival rate was 33.3% in S group, 16.7% in R group, and 25.4% for all patients. Myelosuppression was the most commonly observed adverse effect, with grade 3/4 neutropenia in 30%, and grade 3 thrombocytopenia in 30%. One patient (3.7%) developed neutropenic fever. Respiratory failure and death, possibly related to pulmonary toxicity, was observed in one patient (3.7%). CONCLUSION: monotherapy gemcitabine as second-line agent has limited activity in previously treated SCLC.

Aged↗

PubMed2002

Group sequential methods for an ordinal logistic random-effects model under misspecification.

Interim analyses in clinical trials are planned for ethical as well as economic reasons. General results have been published in the literature that allow the use of standard group sequential methodology if one uses an efficient test statistic, e.g., when Wald-type statistics are used in random-effects models for ordinal longitudinal data. These models often assume that the random effects are normally distributed. However, this is not always the case. We will show that, when the random-effects distribution is misspecified in ordinal regression models, the joint distribution of the test statistics over the different interim analyses is still a multivariate normal distribution, but a sandwich-type correction to the covariance matrix is needed in order to obtain the correct covariance matrix. The independent increment structure is also investigated. A bias in estimation will occur due to the misspecification. However, we will also show that the treatment effect estimate will be unbiased under the null hypothesis, thus maintaining the type I error. Extensive simulations based on a toenail dermatophyte onychomycosis trial are used to illustrate our results.

Biometry↗