Bifurcations in excised larynx experiments

Bifurcation analysis was applied to vocal fold vibration in excised larynx experiments. Phonation onset and vocal instabilities were studied in a parameter plane spanned by subglottal pressure and asymmetry of either vocal fold adduction or elongation. Various phonatory regimes were observed, including single vocal fold oscillations. Selected spectra demonstrated correspondence between these regimes and vocal registers noted in the literature. To illustrate the regions spanned by the various phonatory regimes, two-dimensional bifurcation diagrams were generated. Many instabilities or bifurcations were noted in the regions of coexistence, i.e., regions in which the phonatory regimes overlap. Bifurcations were illustrated with spectrograms and fundamental frequency contours. Where possible, results from these studies were related to clinical observations.

A phase I/II study of high-dose cyclophosphamide, cisplatin, and thioTEPA followed by autologous bone marrow and granulocyte colony-stimulating factor-primed peripheral-blood progenitor cells in patients with advanced malignancies

The purpose of the present study was to determine the maximally tolerated dose of thioTEPA given with fixed high-dose cyclophosphamide (CPA) and cisplatin (cDDP) followed by autologous bone marrow (ABM) with or without granulocyte colony-stimulating factor (G-CSF)-primed peripheral-blood progenitor cells (PBPCs) in patients with advanced malignancies. Patients were required to have histologically documented malignancies and adequate renal, hepatic, pulmonary, and cardiac function. CPA was given at 1,875 mg/m2 per day as a 1-h i.v. infusion for 3 consecutive days, and cDDP was given at 55 mg/m2 per day as a 24-h continuous i.v infusion over 3 days concurrently with CPA. ThioTEPA was given once as a 1-h i.v. infusion (300-900 mg/m2) either following (the first 13 patients) or prior to CPA and cDDP. In all, 31 patients received PBPCs. A total of 46 patients were treated. There were 6 deaths among the 15 patients who did not receive PBPCs (13 received thioTEPA following CPA and cDDP). Among the other 31 patients who received PBPCs (all of whom also received thioTEPA prior to CPA and cDDP), there were 4 deaths, all involving patients with refractory ovarian carcinoma. The main toxicities were mucositis, esophagitis, hepatotoxicity, and nephrotoxicity. The median time required to achieve an absolute neutrophil count of 500 microliter was 10 days (range, 9-12 days) for those who received PBPCs and 15 days (range, 15-34 days) for those who did not receive PBPCs. Altogether, 47% of the major organ toxicities (grades 3 and 4 renal, hepatic, and cardiac toxicities) occurred among the 15 patients who did not receive PBPCs, although these patients received thioTEPA at the lowest 2 dose levels. There were 3 complete responses and 22 partial responses among 35 evaluable patients (overall response rate, 71%), with the median duration of response being 3.5 months (range, 2-17 months). The maximally tolerated dose of thioTEPA was 600 mg/m2 given as a 1-h i.v. infusion on the day prior to CPA and cDDP administration, The combination of high-dose CPA, cDDP, and thioTEPA is a well-tolerated regimen when thioTEPA is given prior to CPA and cDDP and when the combination also includes PBPCs in addition to ABM. This regimen is active in a variety of malignancies.

Different electrophoretic techniques produce conflicting data in the analysis of myocardial samples from dilated cardiomyopathy patients: protein levels do not necessarily reflect mRNA levels

A variety of electrophoretic techniques were used to search for potential causes of human dilated cardiomyopathy (DCM). Northern blots were used to quantify alpha-cardiac and alpha-skeletal muscle actins, and beta-myosin heavy chain mRNAs which are the predominant expressed isoform species. We found a wide range of mRNA levels expressed in both DCM and nondiseased (ND) samples of left ventricles. However, sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) gels of the same heart samples revealed a stable and constant ratio of actin and myosin. Dystrophin deficiency might account for the DCM symptoms and so dystrophin levels of DCM and ND samples were evaluated using Western blots probed with monoclonal antibodies for the N-, C- and mid-rod portions of this protein. We found that dystrophin levels were constant in all 29 DCM and 5 ND samples suggesting that dystrophin deficiency is probably not a contributing cause. We explored the possibility that terminal failure may be due to an apoptotic-like event in the cardiomyocytes. Zymograms of DCM and ND samples revealed a significant increase in DNase I activity in the DCM group compared to the ND samples. These data raise the possibility that end-stage failure may be associated with apoptosis.

Flow cytometry in node-positive breast cancer: cancer and leukemia group B protocol 8869

This report describes a companion flow cytometry study (Cancer and Leukemia Group B (CALGB)--8869) using tumors derived from patients enrolled in a large randomized clinical trial (CALGB-8541) performed on 1,572 patients with early stage, node-positive breast cancer. The CALGB initiated an adjuvant breast cancer trial in 1985 to determine if dose intensification (dose of drug per unit time) of chemotherapy was related to relapse-free and overall survival. Patients were randomized by pretreatment clinical variables to one of three different dosage regimens of chemotherapy. Using a tumor enrichment procedure, 442 paraffin-embedded blocks were analyzed by flow cytometry, and S-phase fraction (SPF) was analyzed by three different methods. Ploidy analysis was performed using standard procedures. Tissue from 90% of the patients was suitable for ploidy analysis, whereas only 68% could be assessed for SPF. With a median follow-up time of 80 months, our results show that ploidy status had no clinical utility, whereas high SPF predicted poorer overall survival. The rectangular fit model for SPF was more predictive of outcome than both the area fit model and a computer fit model (modfit) for SPF. In univariate analysis, patients with a low SPF (< 10%) had a better prognosis than those patients with a high SPF (> 10%), but they responded equally well to the different treatment regimens. Patients with high SPF (> 10%) had longer relapse-free and overall survival to high dose chemotherapy compared to low or standard dose chemotherapy. Multivariate analysis indicated that treatment intensity as well as the number of positive nodes, tumor size, steroid receptor status, and c-erb B-2 expression were significant in predicting overall and disease-free survival. The multivariate analysis, however, revealed that SPF was significant in predicting overall but not disease-free survival, but there was no longer any relationship among SPF, dose intensity, and outcome.

A Bayesian group sequential design for a multiple arm randomized clinical trial

Group sequential designs for randomized clinical trials allow analyses of accruing data. Most group sequential designs in the literature concern the comparison of two treatments and maintain an overall prespecified type I error. As the number of treatments increases, however, so does the probability of falsely rejecting the null hypothesis. Bayesian statisticians concern themselves with the observed data and abide by the likelihood principle. As long as previous analyses do not change the likelihood, these analyses do not change Bayesian inference. In this paper, we discuss a group sequential design for a proposed randomized clinical trial comparing four treatment regimens. Bayesian ideas underlie the design and posterior probability calculations determine the criteria for stopping accrual to one or more of the treatments. We use computer simulation to estimate the frequentists properties of the design, information of interest to many of our collaborators. We show that relatively simple posterior probability calculations, along with simulations to calculate power under alternative hypotheses, can produce appealing designs for randomized clinical trials.

Adaptive assignment versus balanced randomization in clinical trials: a decision analysis

We compare balanced randomization with four adaptive treatment allocation procedures in a clinical trial involving two treatments. The objective is to treat as many patients in and out of the trial as effectively as possible. Randomization is a satisfactory solution to the decision problem when the disease in question is at least moderately common. Adaptive procedures are more difficult to use, but might play a role in clinical research when a substantial proportion of all patients with the disease are included in the trial.

High dose toremifene for estrogen and progesterone receptor negative metastatic breast cancer: a phase II trial of the Cancer and Leukemia Group B (CALGB)

In pre-clinical and limited clinical studies, high doses ( > or = 200 mg/day) of the triphenylethylene derivative toremifene showed activity in estrogen receptor (ER) negative and ER-unknown metastatic breast cancer after progression on tamoxifen, and a mechanism of action independent of hormone receptor binding was speculated. The CALGB conducted a Phase II trial (CALGB 8945) to test the efficacy of high dose toremifene in a population of patients who had hormone receptor-negative, metastatic breast cancer with limited prior chemotherapy exposure, good performance status, and measurable disease. Twenty eligible patients received toremifene at a dose of 400 mg/day orally for 8 weeks. Toxicity was minimal. Nausea was reported by 20% of the patients, lightheadedness by 20%, weight loss by 20%, and hot flashes by 15%. There was no grade 3-4 toxicity. No objective responses were observed, and 5 of 6 patients with stable disease at 8 weeks developed progressive disease at 11 to 33 weeks. High dose toremifene (400 mg/day) is well-tolerated but imparts no detectable activity in hormone receptor-negative, metastatic breast cancer.

Decision making during a phase III randomized controlled trial

Experiments such as clinical trials should be carried out with specific objectives. For example, in a trial designed to prevent disease, specific considerations should be made concerning the impact of the trial on the health of the target population, including the participants in the trial. These objectives should be assessed continually in light of data accumulating from the trial. Accumulating evidence should be judged in the context of changing circumstances external to the trial, and the trial's design possibly modified. An important type of modification is stopping the trial. This is a sequential decision problem that can be addressed using a Bayesian approach and the methods of dynamic programming. As an example we consider a vaccine trial for the prevention of haemophilus influenzae type b. The objective we consider is minimizing the number of cases of this disease in a Native American population over a specified horizon. We assess the prior probability distribution of vaccine efficacy. We also assess the probability of regulatory approval for widespread use of the vaccine, depending on the data presented to the regulatory officials. In deciding whether to continue the trial we weigh the impact of the possible future results by their (predictive) probabilities. We address the sensitivity of the optimal stopping policy to the prior probability distribution, to the assessed probability of regulatory approval, and to the horizon.

Stopping a clinical trial early: frequentist and Bayesian approaches applied to a CALGB trial in non-small-cell lung cancer

In May 1984, the Cancer and Leukemia Group B (CALGB) opened a phase III clinical trial for patients with stage III non-small-cell lung cancer (NSCLC). The experimental design entailed randomization of 240 patients equally to one of two treatments: radiotherapy alone or chemotherapy followed by radiotherapy. The original design was a fixed sample size design with the intent to analyse the results after 190 deaths. Shortly after the trial began, it was decided to apply group sequential concepts by using a truncated O'Brien-Fleming stopping rule, implemented via a Lan-DeMets alpha-spending function. A study monitoring committee was established to review the analyses as they were produced. The study was stopped at the fifth interim analysis in May 1987 after 155 eligible patients had been entered. This paper reviews the statistical and other considerations leading to this decision and presents later follow-up information on these patients. Some Bayesian alternatives to the standard frequentist approaches are also explored and it is demonstrated how these alternatives provide a natural way to address many of the issues raised in monitoring clinical trials.

Interpretation of biomechanical simulations of normal and chaotic vocal fold oscillations with empirical eigenfunctions

Empirical orthogonal eigenfunctions are extracted from biomechanical simulations of normal and chaotic vocal fold oscillations. For normal phonation, two dominant empirical eigenfunctions capture the vibration patterns of the folds and exhibit a 1:1 entrainment. The eigenfunctions show some correspondence to theoretical low-order normal modes of a simplified, three-dimensional elastic continuum, and to the normal modes of a linearized two-mass model. The eigenfunctions also facilitate a physical interpretation of energy transfer mechanisms in vocal fold dynamics. Subharmonic regimes and chaotic oscillations are observed during simulations of a lax cover, in which case at least three empirical eigenfunctions are necessary to capture the resulting vocal fold oscillations. These chaotic oscillations might be understood in terms of a desynchronization of a few of the low-order modes, and may be related to mechanisms of creaky voice or vocal fry. Furthermore, some of the empirical eigenfunctions captured during complex oscillations correspond to higher-order normal modes described in earlier theoretical work. The empirical eigenfunctions may also be useful in the design of lower-order models (valid over the range for which the empirical eigenfunctions remain more or less constant), and may help facilitate bifurcation analyses of the biomechanical simulation.

c-erbB-2 expression and response to adjuvant therapy in women with node-positive early breast cancer

BACKGROUND

The role of molecular markers in predicting the response to treatment of breast cancer is poorly defined. The Cancer and Leukemia Group B (CALGB) conducted a randomized adjuvant-chemotherapy trial (CALGB 8541) comparing three doses (high, moderate, and low) of cyclophosphamide, doxorubicin, and fluorouracil in 1572 women with node-positive breast cancer. This study (CALGB 8869) was designed to determine whether the DNA index, the S-phase fraction, c-erbB-2 expression, or p53 accumulation could be used as a marker to identify a subgroup of patients more likely than others to benefit from high doses of chemotherapy.

METHODS

Tissue blocks were obtained from 442 patients randomly selected from the larger CALGB trial. Paraffin sections from the primary lesions were analyzed for DNA content, S-phase fraction, c-erbB-2 expression, and p53 accumulation.

RESULTS

Patients randomly assigned to the high-dose regimen of adjuvant chemotherapy had significantly longer disease-free and overall survival if their tumors had c-erbB-2 overexpression. No further information was gained by adding the data on S-phase fraction or p53 accumulation to the analysis. There was no clear evidence of a dose-response effect in patients with minimal or no c-erbB-2 expression.

CONCLUSIONS

There is a significant dose-response effect of adjuvant chemotherapy with cyclophosphamide, doxorubicin, and fluorouracil in patients with overexpression of c-erbB-2 but not in patients with no c-erbB-2 expression or minimal c-erbB-2 expression. Overexpression of c-erbB-2 may be a useful marker to identify the patients who are most likely to benefit from high doses of adjuvant chemotherapy.

A case for Bayesianism in clinical trials

This paper describes a Bayesian approach to the design and analysis of clinical trials, and compares it with the frequentist approach. Both approaches address learning under uncertainty. But they are different in a variety of ways. The Bayesian approach is more flexible. For example, accumulating data from a clinical trial can be used to update Bayesian measures, independent of the design of the trial. Frequentist measures are tied to the design, and interim analyses must be planned for frequentist measures to have meaning. Its flexibility makes the Bayesian approach ideal for analysing data from clinical trials. In carrying out a Bayesian analysis for inferring treatment effect, information from the clinical trial and other sources can be combined and used explicitly in drawing conclusions. Bayesians and frequentists address making decisions very differently. For example, when choosing or modifying the design of a clinical trial, Bayesians use all available information, including that which comes from the trial itself. The ability to calculate predictive probabilities for future observations is a distinct advantage of the Bayesian approach to designing clinical trials and other decisions. An important difference between Bayesian and frequentist thinking is the role of randomization.

Degradation of dicamba by an anaerobic consortium enriched from wetland soil

The biodegradability of dicamba was investigated under anaerobic conditions with a consortium enriched from wetland soil. Degradation proceeded through an initial demethylation reaction, forming 3,6-dichlorosalicylic acid, followed by reductive dechlorination, forming 6-chlorosalicylic acid. The consortium, consisting of a sulfate reducer, three methanogens, and a fermenter, was unable to mineralize the aromatic ring.

Fundamental frequency stability in functional dysphonia

Functional dysphonia is a term applied to voice disorders for which there is an absence of apparent structural change in the larynx. The aim of this work was to investigate how functional dysphonia may differ acoustically from other types of dysphonia. Fundamental frequency profiles for steady vowels were generated using a software program called GLIMPES (Glottal Imaging by Processing External Signals). The fundamental frequency variations were found to be unimodal in normal individuals. In contrast, the variations for dysphonic patients were sometimes bi-modal or multi-modal due to the presence of subharmonics or low-frequency modulations. The appearance of these patterns was generally related to the severity of the dysphonia rather than to its etiology.

Endoscopic release of the carpal tunnel: a randomized prospective multicenter study

A 10-center randomized prospective multicenter study of endoscopic release of the carpal tunnel was carried out. Surgery was performed with a new device for transecting the transverse carpal ligament while control hands were treated with conventional open surgery. There were 122 patients in the study; 25 had carpal tunnel surgery on both hands and 97 had surgery on one hand. Of the surgical procedures, 65 were in the control group and 82 were in the device group. The endoscopic device was coupled to a fiberoptic light and a video camera. A trigger-activated blade was used to incise the transverse carpal ligament. After surgery, the best predictors of return to work and to activities of daily living were strength and tenderness variables. For patients in the device group with one affected hand, the median time for return to work was 21 1/2 days less than that for the control group. Two patients treated with the endoscopic device required reoperation by open surgical decompression; only one of these had incomplete release with the device. Two patients in the device group experienced transient ulnar neurapraxia.

A million dollar measles outbreak: epidemiology, risk factors, and a selective revaccination strategy

Between February 8 and April 4, 1986, an outbreak of measles occurred in the State of Arkansas. A total of 489 suspected measles cases were reported from 53 counties; 86 schools statewide reported suspected measles cases. There were 284 cases confirmed in 18 counties; 23.6 percent among students in one university and 41.2 percent among students in kindergarten through 12th grade in 32 schools. An epidemiologic investigation was carried out to evaluate risk factors for vaccine failure and to assess the effectiveness of a selective revaccination strategy in the outbreak setting. A cohort study conducted at a junior high school showed that, compared with students vaccinated against measles at ages 15 months or older, those vaccinated at ages 12-14 months had a three-fold increased risk of measles (relative risk 3.2, 95 percent confidence interval 1.5, 6.9). For schools reporting measles, the Arkansas Department of Health and the Department of Education jointly required reimmunization of students vaccinated at ages younger than 15 months and the exclusion of students not vaccinated at ages 15 months or older until they were vaccinated or until 2 weeks after the last rash onset. To implement these recommendations, more than 100,000 doses of combined measles-mumps-rubella vaccine were distributed at a cost greater than $1 million.