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J Benichou

Publications and source records attributed to J Benichou.

At least 73 records · Page 4Linked to original sources
PubMed1993

Role of HTLV-I in development of non-Hodgkin lymphoma in Jamaica and Trinidad and Tobago. The HTLV Lymphoma Study Group.

Human T-cell lymphotropic virus type I (HTLV-I) has been implicated in the aetiology of adult T-cell leukaemia/lymphoma in Japan and elsewhere, particularly the Caribbean. We have carried out parallel case-control studies in Jamaica and in Trinidad and Tobago to quantify the role of HTLV-I in the development of non-Hodgkin lymphoma (NHL). 135 cases of NHL were enrolled in Jamaica and 104 in Trinidad and Tobago. Controls were selected from patients treated in the same wards or clinics at the same time as the cases. Overall, patients with NHL were 10 times more likely than were controls to be seropositive for HTLV-I (Jamaica odds ratio 10.3 [95% CI 6.0-18.0], Trinidad and Tobago 14.4 [7.6-27.2]). In both countries the association between NHL and HTLV-I was greatest for T-cell lymphomas (18.3 [9.5-35.6] and 63.3 [25-167]). Among T-cell lymphomas especially, there was no significant difference between men and women in the association between NHL and HTLV-I, but there was a significant inverse relation between age and likelihood of HTLV-I seropositivity. B-cell lymphomas were predominant in the older age groups and were not associated with HTLV-I seropositivity. These findings are consistent with the hypothesis that early life exposure to HTLV-I is important for risk of subsequent ATL. Prevention of vertical transmission of HTLV-I could reduce by 70-80% cases of NHL in people under 60 years in this region.

Adult↗
PubMed1993

A computer program for estimating individualized probabilities of breast cancer.

A computer program is presented for estimating the absolute risk of developing breast cancer over a specified age interval for women with combinations of five risk factors, namely age at menarche, age at first live birth, family history of breast cancer, number of previous breast biopsies, and presence of atypical hyperplasia in biopsy specimens. Statistical methods have been developed and applied to data from the Breast Cancer Detection and Demonstration Project to obtain (i) point estimates of absolute risk by combining relative risk estimates from case-control data and estimated composite incidence rates from cohort data, and (ii) confidence intervals by using implicit delta-method arguments. The program is interactive and easy to use and is therefore well suited to assist in medical counseling. For instance, women with high estimated risk might be advised to undergo a program of frequent surveillance with mammography. An executable version for IBM-compatible PCs is available from the author upon submission of a PC diskette formatted with MS-DOS.

Adult↗
PubMed1991

Analysis of phase II clinical trials in haematology and oncology: comparison of the triangular test to the usual methods.

Phase II cancer clinical trials are non-comparative trials which are designed to determine whether the response rate p to the treatment under study is greater than a certain value p0, that is, to test H0, given by p less than or equal to p0 against H1 given by p greater than po. By choosing type I error alpha and the power 1-beta and by specifying H1, that is, by choosing a clinically relevant improvement p1), one can compute the number of patients N to be included for a fixed-sample approach. Various other approaches have been proposed such as multistage methods and Wald's continuous sequential probability ratio test (SPRT). As an alternative approach, we extended the triangular test (TT), proposed by Whitehead for comparative trials, to the situation of non-comparative trials with a binary outcome. We expressed H0 and H1 in terms of the log odds-ratio statistics, namely log [p(1-p0)/p0-(1-p)]. With this choice, the two statistics of interest, Z and V, have simple expressions: Z is the difference between the observed number of positive outcomes and the expected number under H0 and V is the variance of Z under H0. After every group of n patients, Z is plotted against V, and the trial proceeds until a boundary is crossed. In our simulations, type I error alpha and the power 1-beta were close to nominal values with the TT and the average sample size was close to Wald's continuous SPRT and compared favourably with the multistage methods proposed by Herson and Fleming. Given its statistical properties and its easy use, the TT should be considered for planning and analysing cancer phase II trials.

Clinical Trials as Topic↗
PubMed1991

Methods of adjustment for estimating the attributable risk in case-control studies: a review.

In the 1980's, progress was made in adjusting estimates of the attributable risk (AR) for confounding factors and in calculating associated confidence intervals. In this paper, methods of adjustment for estimation of the AR in case-control studies are reviewed. The limitations and problems associated with two methods based on stratification, the weighted-sum approach and the Mantel-Haenszel approach, are discussed. They include small-sample bias with the weighted-sum approach and the difficulty of taking interaction into account with the Mantel-Haenszel approach. A third method based on logistic regression is reviewed. It is argued that this latter method has the greatest generality and flexibility, and includes the two other approaches as special cases. Throughout the paper, an example of a case-control study of oesophageal cancer illustrates the use of the methods described.

Alcohol Drinking↗
PubMed1990

Failure of the perioperative PCV neoadjuvant polychemotherapy in resectable bronchogenic non-small cell carcinoma. Results from a randomized phase II trial.

In 1985, the authors began a phase II study to assess the PCV perioperative polychemotherapy (cisplatin 100 mg/m2, cyclophosphamide 600 mg/m2, vindesine 3 mg/m2) in patients with resectable bronchogenic non-small cell carcinoma. Patients were randomized to receive either two preoperative courses of PCV chemotherapy, surgery, and two postoperative courses of PCV chemotherapy (PCV group) or immediate surgery (surgery group). A staging procedure using the CT scan was performed before randomization and, additionally, before surgery in the PCV group. There were 26 randomized patients, 13 in each group. In the PCV group, 11 patients agreed to receive the two preoperative courses of chemotherapy. A response was observed in five patients (45%), and a progression was observed in four patients (36%) leading to a cancellation of surgery in two of them. Postoperative care was the same for each group. Although no death could be related to chemotherapy, it was decided to stop entering new patients into this trial because of the rate of preoperative progression in the PCV group.

Adult↗
PubMed1990

Application of the triangular test to phase II cancer clinical trials.

Phase II cancer clinical trials are primarily designed to determine whether the response rate p to the treatment under study is greater than a specified value p0, that is to test the null hypothesis H0: p less than or equal to p0 against an alternative hypothesis H1 : p greater than p0 specified by p = p1. As an alternative to the single and multistage procedures and to Wald's continuous sequential probability ratio test (SPRT), we applied the group sequential methods proposed by Jones and Whitehead, namely the triangular test (TT) and the discrete SPRT, to the comparison of p with p0, and we expressed H0 and H1 in terms of the log odds-ratio statistic log [p(1 - p0)/p0(1 - p)]. A stimulation study showed that both the TT and the discrete SPRT had type I error and power close to the nominal values, and they compared favourably with multistage methods in terms of the average sample size.

Clinical Trials as Topic↗
PubMed1990

Variance calculations and confidence intervals for estimates of the attributable risk based on logistic models.

The attributable risk (AR), defined as AR = [Pr(disease) - Pr(disease/no exposure)]/Pr(disease), measures the proportion of disease risk that is attributable to an exposure. Recently Bruzzi et al. (1985, American Journal of Epidemiology 122, 904-914) presented point estimates of AR based on logistic models for case-control data to allow for confounding factors and secondary exposures. To produce confidence intervals, we derived variance estimates for AR under the logistic model and for various designs for sampling controls. Calculations for discrete exposure and confounding factors require covariances between estimates of the risk parameters of the logistic model and the proportions of cases with given levels of exposure and confounding factors. These covariances are estimated from Taylor series expansions applied to implicit functions. Similar calculations for continuous exposures are derived using influence functions. Simulations indicate that those asymptotic procedures yield reliable variance estimates and confidence intervals with near nominal coverage. An example illustrates the usefulness of variance calculations in selecting a logistic model that is neither so simplified as to exhibit systematic lack of fit nor so complicated as to inflate the variance of the estimate of AR.

Alcohol Drinking↗
PubMed1990

Methodological aspects of a clinical trial in chronic lymphocytic leukemia: necessity to develop new biostatistical methods.

The CLL protocol allowed a better understanding of the natural history of Chronic Lymphocytic Leukemia and an assessment of several treatment strategies. From the point of view of biostatistical research, it raised several important problems. In this paper, we show the interest of applying sequential methods, particularly the triangular test. Other biostatistical problems raised by the CLL 80 protocol are still not, or only partially, resolved. They include taking into account prior belief about treatment benefit in sample size calculations, using surrogate endpoints, developing methods to take into account the causes of death, to analyse repeated measurements, and to assess and compare staging systems.

Biometry↗
PubMed1990

Estimates of absolute cause-specific risk in cohort studies.

In this paper we study methods for estimating the absolute risk of an event c1 in a time interval [t1, t2], given that the individual is at risk at t1 and given the presence of competing risks. We discuss some advantages of absolute risk for measuring the prognosis of an individual patient and some difficulties of interpretation for comparing two treatment groups. We also discuss the importance of the concept of absolute risk in evaluating public health measures to prevent disease. Variance calculations permit one to gauge the relative importance of random and systematic errors in estimating absolute risk. Efficiency calculations were also performed to determine how much precision is lost in estimating absolute risk with a nonparametric approach or with a flexible piecewise exponential model rather than a simple exponential model, and other calculations indicate the extent of bias that arises with the simple exponential model when that model is invalid. Such calculations suggest that the more flexible models will be useful in practice. Simulations confirm that asymptotic methods yield reliable variance estimates and confidence interval coverages in samples of practical size.

Biometry↗
PubMed1986

[Application of sequential methods in randomized clinical trials with censored response criteria].

In randomized clinical trials with a censored response criterion, it is common practice to perform interim analyses, especially for reasons of medical ethics. Sequential methods allow for repeated testing. Three sequential methods are well adapted to censored data: the group sequential analysis, the sequential probability ratio test and the triangular test. Among them, the triangular test has the best statistical properties. The influence of the frequency of the analyses on the statistical properties of sequential methods has been studied by simulation: sequential analyses need not be performed more frequently than interim analyses. Sequential methods have been applied to several randomized clinical trials. The results are briefly reported for two of them. The ability of the triangular test and of the sequential probability ratio test to reach conclusions early when there is no difference between two compared treatments is supported by these two examples. Moreover, careful patient follow-up must be planned in the protocol in order to reduce the time for data updating and to perform sequential analyses at the required frequency. It appears well-founded to propose the use of the triangular test in randomized clinical trials with a censored response criterion. Four types of analyses with different aims must be planned in the protocol.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1982

[Tumours of the hepatic hilus. Palliative treatment by trans-hepatobiliary T-tube drainage (author's transl)].

Non-resectable tumours of the hepatic hilus require palliative treatment, and this can be achieved by means of a trans-hepatobiliary T-shaped tube devised by the authors. The longer branch of the tube going through the bile ducts and liver can as easily be removed when obstructed as a U-shaped tube. The shorter branch going through the common bile duct ensures internal biliary drainage. The drain can easily be changed under fluoroscopy.

Common Bile Duct↗
PubMed1981

[Early jaundice after orthotopic liver transplantation. The role of ischaemia (author's transl)].

The purpose of this experimental study was to identify the cause of early cholestatic jaundice occurring after orthotopic liver transplantation. The role of ischaemia was investigated in dogs undergoing auto-transplantation of the liver preserved for two hours. The animals developed early cholestasis with lesions that were markedly different from the graft-rejection lesions observed in a control group, being restricted to the cells and canaliculi of the central lobular area. The results of this work have made it possible to avoid overdosage with immunosuppressive drugs in a patient who had recently undergone orthotopic liver transplantation.

Animals↗