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Biomedical subjects

B G Birkhead

Publications and source records attributed to B G Birkhead.

11 recordsLinked to original sources
PubMed1989

Factors at presentation influencing the prognosis in breast cancer.

Presentation data on 607 breast cancer patients treated by a variety of modalities at Guy's Hospital, London, have been analysed using the Cox proportional hazards model, to identify factors associated with length of overall survival. When deaths attributable to causes other than breast cancer were treated as censoring events, the significant factors were found to be stage, mode of treatment, menstrual status and tumour size. The analysis was repeated for the subgroup of 326 patients treated by modified radical mastectomy. Four variables: stage, age at menarche, menstrual status and age were found to be significantly associated with both overall survival and length of distant recurrence-free interval. These factors have been combined to create a prognostic index which has been used to define subgroups of patients with different prognosis. The index has been validated on a separate group of 457 modified radical mastectomy patients treated at the same hospital.

Adult↗
PubMed1988

A mathematical model of drug resistance applied to treatment for small-cell lung cancer.

A mathematical model has been applied to patients with small-cell lung cancer (SCLC) in order to estimate the proportions of resistant and sensitive tumor at presentation, and the efficacy of the treatment, measured in terms of proportions of tumor killed with each cycle of therapy. The model uses estimates of tumor volume obtained from computed tomographic (CT) scans of the chest before each course of chemotherapy. Application of the model to a trial using single-agent high-dose cyclophosphamide (HDC) showed that HDC killed approximately 94% of the sensitive tumor on each application, but that the proportion of tumor resistant to HDC rose from an average of 1% to an average of 15% after the first cycle, assuming a 30-day tumor doubling time. These estimates proved fairly insensitive to different assumptions about tumor doubling time and inaccuracies in volume measurement and may thus provide a useful additional evaluation technique for some clinical trials.

Carcinoma, Small Cell↗
PubMed1987

Towards an assessment of toxicity in the treatment of ovarian cancer.

Using data from a randomised clinical trial of two platinum drugs at The Royal Marsden Hospital, London, a descriptive model of toxicity has been developed and tested. Toxicity manifests itself in reducing the effectiveness of different body processes; five were selected in this study as being most critical. The model summarises and combines data from these five sites in terms of a clinician's assessment of the associated risk to the patient. It is hoped that the approach will help clarify toxicity information for use in patient management decision-making and in the reporting of clinical trial results.

Antineoplastic Agents↗
PubMed1987

A mathematical model of the development of drug resistance to cancer chemotherapy.

A mathematical model incorporating descriptions of tumour growth kinetics and the effects of cytotoxic chemotherapy on established tumours, is presented. It is shown how models of this kind may be used to investigate the potential of hypothetical chemotherapy strategies, and to identify general principles for successful treatment. The model is intended to be an aid to clinicians designing new chemotherapy programmes for diseases in which progress has been disappointing.

Antineoplastic Agents↗
PubMed1985

High-dose cyclophosphamide in small-cell carcinoma of the lung.

Eighteen patients with untreated small-cell cancer of the lung have been treated with cyclophosphamide 200 mg/kg on two occasions at an interval of four weeks. An additional eight patients received etoposide in addition to cyclophosphamide. Measurements of tumor volume were made by thoracic computed tomographic (CT) scan before and after each cycle. When compared with our previous study in which only one cycle of cyclophosphamide was given, the double procedure did not increase response rate, decrease the incidence of local relapse, or prolong the relapse-free interval. Survival after relapse was shorter with two cycles of chemotherapy mainly due to greater difficulty in administering further chemotherapy. The CT scans showed a decrease in tumor volume from 99.2 cc to 21 cc after the first cycle, but a smaller decrease to 14.1 cc after the second. These results show that the rapid emergence of drug resistance imposes limitations on the use of very high-dose cytotoxic chemotherapy.

Adult↗
PubMed1985

Mathematical model of remission duration in acute myelogenous leukemia.

A mathematical model of disease-free survival in acute myelogenous leukemia is formulated in terms of proliferation of the leukemic stem cell compartment. A survivorship function is described which allows for the possibility that some patients may be cured of their disease and which captures the main features of experimental remission-duration curves. The model is used to investigate the effect of the amount of residual disease and the growth rate of the stem cell population on the length of remissions and the chances for cure. A method of comparing clinical trials, with potential for explanatory inference, is exemplified.

Cell Division↗
PubMed1982

Short-term treatment for acute myelogenous leukaemia.

Short-term treatment with doxorubicin, cytarabine, and 6-thioguanine was given to 91 consecutive adults with acute myelogenous leukaemia. Fifty patients received high doses (regimen I) and 41 very high doses (regimen II). Where possible, six treatment cycles were given (total dose of doxorubicin 450 mg/m2) regardless of the number of cycles required to achieve complete remission. No additional treatment was given. The remission rate was significantly higher with regimen I than with regimen II (34/50 compared with 15/41, p less than 0.01), the latter, more intensive regimen being associated with a greater incidence of fatal infection (13/41 compared with 5/50, p less than 0.01). Duration of remission was, however, significantly longer with regimen II (p less than 0.05); the median has not yet been reached after a minimum follow-up of two years. Intensive short-term treatment is a feasible strategy for the treatment of acute myelogenous leukaemia.

Adolescent↗
PubMed1982

Application of Jackson, Aspden Acute Myeloid Leukaemia model.

The comparison of a series of small clinical trials into the treatment of Acute Myelogenous Leukaemia at St Bartholomew's Hospital, London, is described using a previously published mathematical model. The work demonstrates the value of a coherent presentation and analysis of available information in assisting clinicians in their decision-making.

Clinical Trials as Topic↗
PubMedDate not supplied

Reliability and consistency of bone marrow assessments of complete remission in acute myelogenous leukaemia.

An experiment is described which was designed to investigate the level of variability in the assessment of bone marrow remission in Acute Myelogenous Leukaemia (AML). The inter-rater reliability and individual consistency of three haematologists at St Bartholomew's Hospital, London, are analysed using their assessments of cellularity, percent blast cells and marrow status for fifty bone marrow samples.

Bone Marrow↗