Categorising continuous variables

Altman, D G

doi:10.1038/bjc.1991.441

Cited by 100 publications

(41 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Survival curves were derived from Kaplan-Meier (Kaplan and Meier, 1958) estimates, and survival rates are presented with their standard deviation. The problem of using the so-called 'optimal' cut-points, which could overestimate the effect of uPA and p53, led us to use pre-specified cut-points when examining the functional relationship between these markers and outcome (Altman, 1991;Altman et al, 1994). We considered four prespecified cut-points corresponding to the 20th, 40th, 60th and 80th percentiles in the overall population.…”

Section: Methodsmentioning

confidence: 99%

Prognostic value of uPA and p53 accumulation measured by quantitative biochemical assays in 1245 primary breast cancer patients: a multicentre study

Broët

Spyratos

Romain³

et al. 1999

Br J Cancer

View full text Add to dashboard Cite

SummaryThe purpose of this retrospective multicentre study was to assess the prognostic value of urokinase plasminogen activator (uPA) and p53 levels in a large series of primary breast cancer, using an automatic quantitative luminometric method. Samples of 1245 operable breast tumours were collected from seven French institutions and patients were followed for a median of 75 months. The median uPA and p53 levels assayed in cytosols by means of the immunoluminometric technique (LIA) were 0.31 and 0.20 ng mg -1 of protein respectively. In univariate analysis, high levels of uPA and p53 were associated with shorter disease-specific survival, disease-free interval, and distant recurrence-free interval. The 5-year survival rates were 95.5% among patients with uPA values below the 20th percentile, and 77.5% in those with values above the 80th percentile. The 5-year survival rates were 91.0% in patients with p53 values below the 20th percentile, and 77.6% in those with values above the 80th percentile. In multivariate analysis, the risk of disease-related death increased with uPA levels after adjustment for tumour size, histological grade, lymph node involvement, and estrogen receptor status. A high level of uPA was also related to a shorter disease-free interval and distant recurrence-free interval. In node-negative patients, a high level of uPA remained strongly related to the three outcomes. When adjusted for other prognostic factors, p53 was no longer significantly related to the outcomes. Given its rapidity and simple application to routinely prepared cytosols, this LIA may be useful for evaluating the prognostic impact of uPA in primary breast cancer, particularly in node-negative patients. According to our results, the prognostic value of p53 accumulation is limited when uPA is included in multivariate analysis.

show abstract

Section: Methodsmentioning

confidence: 99%

Prognostic value of uPA and p53 accumulation measured by quantitative biochemical assays in 1245 primary breast cancer patients: a multicentre study

Broët

Spyratos

Romain³

et al. 1999

Br J Cancer

View full text Add to dashboard Cite

show abstract

“…Five papers reported using the 'optimal' cutoff point approach, which is not recommended (Altman, 1992;Altman et al, 1994 We also identified many presentational problems. In particular, there was a general tendency to present results as P-values without quantitative results, and an absence of confidence intervals.…”

Section: Miscellaneamentioning

confidence: 99%

Review of survival analyses published in cancer journals

Altman

Stavola²,

Love³

et al. 1995

Br J Cancer

Self Cite

368

296

View full text Add to dashboard Cite

Summary Survival analysis has found widespread applications in medicine in the last 10-15 years. However, there has been no published review of the use and presentation of survival analyses. We have carried out a systematic review of the research papers published between October and December 1991 in five clinical oncology journals. A total of 132 papers were reviewed. We looked at several aspects of study design, data handling, analysis and presentation of the results. We found that almost half of the papers did not give any summary of length of follow-up; that in 62% of papers at least one end point was not clearly defined; and that both logrank and multivariate analyses were frequently reported at most only as P-values [63/84 (75%) Survival analysis has found widespread applications in medicine in the last 10-15 years (Andersen, 1991), particularly in clinical oncology, and its correct application and presentation is critically relevant for much of the cancer literature. Although the use of statistical methods in medicine has been subjected to much scrutiny (see Altman, 1982Altman, , 1991, we believe that there has not been any published review of the use of survival analysis methods in medical journals. Hence, we have carried out a systematic review of the appropriateness of the application and presentation of survival analyses in clinical oncology journals. We have focused on the size of the studies being published, the adequacy of the description of the data analysed (with particular interest given to the length and quality of follow-up and the clarity of the end points of interest) and the choice and quality of univariate, multivariate and graphical analyses. In the light of disappointing findings, we discuss existing guidelines and present some new guidelines aimed in particular at presentation. MethodsWe examined all papers published in British Journal of Cancer, European Journal of Cancer, Journal of Clinical Oncology and American Journal of Clinical Oncology between October and December 1991 which included analyses of survival data. There were 132 papers which reported at least one of the following: Kaplan-Meier or actuarial survival curves; logrank or related tests; parametric or semiparametric survival analyses. Those papers with survival data which did not present any of these analyses, and thus were not included, were largely phase I or II clinical trials.The 132 papers were reviewed using a standard form that had been tested in a small pilot study of 20 papers which were read by all four authors. When the form was finalised each paper was read by two of the authors according to a balanced randomisation scheme. Disagreements between reviewers were resolved in paired discussions and by discussion between all four reviewers on the rare occasions when it was necessary.The assessment form included separate sections relating to distinct aspects of each paper. It also included the time taken by each author to extract the information from the paper onto the form as an indication of the clarity of each...

show abstract

“…Biochemical measurements of ER activity have long been known to be of value for predicting the outcome of endocrine therapy (NIH Consensus Meeting 1974, reported by McGuire et al, 1975) and also as a guide to prognosis (Walt et al, 1976;Knight et al, 1977). Since 1980, however, the use and acceptance of receptor assays in the management of breast cancer has had a chequered history for a variety of reasons, including: poor quality control of biochemical assays; poor control of specimen quality; changes in methodology; use of receptor measurements as a discontinuous variable (Altman, 1991;Simon and Altman, 1994) with an arbitrary 'cut-off' to decide receptor 'positivity/ negativity'; the advent of the relatively non-toxic endocrine agent, tamoxifen; initial reports that benefit from adjuvant therapy with tamoxifen was unrelated to receptor activity (Novaldex Adjuvant Trial Organisation, 1983), although subsequent reports have disagreed (Rose et al, 1985;Scottish Breast Trials Committee, 1987;De Placido et al, 1990;Early Breast Cancer Trialists, 1992); the need for an adequate tumour specimen (50-250 mg); the advent of the Breast Cancer Screening Program (Forrest, 1986), which yields many impalpable tumours too small for biochemical assay; the widely quoted view that '8-10%' 'receptornegative' tumours respond to endocrine therapy -likely to be untrue for the reasons discussed by, for example, Wittliffe, (1988), andRobertson, (1996); the misconception that tumour grade provides exactly the same information as oestrogen receptor measurements, but at a lesser cost.…”

mentioning

confidence: 99%

How best to express oestrogen receptor activity

Hawkins

2000

European Journal of Cancer

View full text Add to dashboard Cite

Categorising continuous variables

Cited by 100 publications

References 8 publications

Prognostic value of uPA and p53 accumulation measured by quantitative biochemical assays in 1245 primary breast cancer patients: a multicentre study

Prognostic value of uPA and p53 accumulation measured by quantitative biochemical assays in 1245 primary breast cancer patients: a multicentre study

Review of survival analyses published in cancer journals

How best to express oestrogen receptor activity

Contact Info

Product

Resources

About