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Biomedical subjects

P Rhodes

Publications and source records attributed to P Rhodes.

At least 19 recordsLinked to original sources
PubMed1992

Obesity at diagnosis of breast carcinoma influences duration of disease-free survival.

OBJECTIVE: To study disease-free survival at 10 years in relation to obesity at the time of diagnosis. DESIGN: A prospective study of consecutively treated patients with primary breast cancer. SETTING: Memorial Sloan-Kettering Cancer Center, New York. PATIENTS: Nine hundred twenty-three women treated by mastectomy and axillary dissection. MAIN RESULTS: Women who were obese (25% or more over optimal weight for height) at the time of primary breast cancer treatment were at significantly greater risk for recurrence (42%) compared with nonobese patients (32%) 10 years after diagnosis (P less than 0.01). In multivariate analyses, obesity remained a statistically significant prognostic factor after controlling for measured tumor size, number of positive axillary lymph nodes, age at diagnosis, and adjuvant chemotherapy with a hazard ratio of 1.29 (95% CI, 1.0 to 1.67). When analyses were restricted to the 557 patients free of lymph node metastases, the hazard ratio of recurrence associated with obesity was 1.59 (CI, 1.06 to 2.39); 32% of obese patients developed recurrent disease compared with 19% of nonobese women. CONCLUSIONS: Obesity at the time of diagnosis is a significant prognostic factor that may limit the reduction in breast cancer mortality attainable through detection at an early stage of disease. Because obesity and the risk for breast cancer increase with age, interventions that encourage weight control may influence breast cancer survival rates.

Adult↗
PubMed1991

Timing of breast cancer excision during the menstrual cycle influences duration of disease-free survival.

OBJECTIVE: To study disease-free survival at 10 years in relation to timing of breast tumor excision during the menstrual cycle. DESIGN: A prospective study of consecutively treated patients with primary breast cancer. SETTING: Memorial Sloan-Kettering Cancer Center, New York. PATIENTS: Two hundred and eighty-three premenopausal patients treated by mastectomy and axillary dissection. MAIN RESULTS: When the tumor was excised during the follicular phase, approximated by setting the putative day of ovulation on day 14 after the onset of last menses, a higher recurrence risk (43%) was observed compared with excision later in the menstrual cycle (29%, P = 0.02). The rate peaked among patients treated between days 7 and 14 and was lowest between days 20 and 30. Multivariate analysis using the Cox regression model to control for tumor size, nodal status, estrogen receptor status, adjuvant chemotherapy, and family history indicated that the hazard rate of breast cancer recurrence after excision during the follicular phase was 1.53 (95% Cl, 1.02 to 2.29). Stratification by nodal status indicated that the effect of phase was statistically significant only among patients with positive nodes (hazard ratio, 2.10; Cl, 1.19 to 3.70). CONCLUSIONS: Our results support the hypothesis that the risk for recurrence may be affected by the hormonal milieu of the menstrual cycle; these findings must be confirmed, however, by a prospective study in which cycle phase at time of tumor excision is biochemically documented.

Adult↗
PubMed1991

MICs of ciprofloxacin and trimethoprim for Escherichia coli: influence of pH, inoculum size and various body fluids.

The influence of pH, inoculum size, human urine and prostatic extract on the MICs of ciprofloxacin and trimethoprim for Escherichia coli was investigated. There was no influence by the bacterial inoculum size within wide ranges on either drug. An increase in pH had a variable influence on the MICs of trimethoprim for E. coli but lowered those of ciprofloxacin considerably. Human prostatic extract increased the trimethoprim MIC for E. coli but lowered those of ciprofloxacin as compared to Mueller Hinton broth. Human urine increased the MICs of both drugs for E. coli.

Animals↗
PubMed1991

An evaluation of the putative human mammary tumour retrovirus associated with peripheral blood monocytes.

The primary aims of this study were purification and molecular cloning of a putative retrovirus designated human mammary tumour virus (HMTV). However, our preliminary unpublished data of negative reverse transcriptase (RT) activity in ostensibly 'infected' cells led us to re-examine the evidence for this virus; namely multinucleate giant cell (MNGC) formation and RT activity in cultured blood monocytes from breast cancer patients versus benign breast tumour and normal control subjects. MNGCs from by fusion of monocytes and we estimated the total number of cell fusions which had occurred after 10 days of culture in vitro by counting cells with two, three, four and five or more nuclei (n) and by measuring the density of adherent mononuclear cells for each subject studied. We found no clear-cut difference in MNGC formation between the three subject groups. Moreover, a substantial number of cultures, encompassing the three groups, showed far more MNGCs per 10(5) monocytes than previously reported. Various parametric and nonparametric statistical analyses were performed on the multinucleate cell data and only one parametric test, which utilised the density of monolayers as a co-variate, showed a statistically significant difference at the 5% level between the breast cancer and the normal subject groups. We observed marked subject-to-subject variation in multinucleate cell formation and we suggest that the evidence for a difference between the breast cancer and the normal groups is marginal. Further, MNGC formation by breast cancer monocytes may not be attributed to the presence of a retrovirus since 5'-Azacytidine (AZA), an agent known to stimulate replication of latent retroviruses showed no effect on the MNGC formation. In addition, culture supernatants from the three groups were assayed for RT activity and no test sample gave a significant signal above background. Preliminary transmission electron microscopy analysis failed to identify viral particles in MNGCs.

Adult↗
PubMed1991

Determinants of vaccination in an urban population in Conakry, Guinea.

A community survey was conducted in 1989 in Conakry, Guinea to determine reasons for low vaccination coverage. Some 377 children aged 12-23 months and their guardians were studied, of whom 204 (54%) had vaccination records. According to their records 19% of children were fully and correctly vaccinated. Thirty-nine incompletely vaccinated children (19% of those with records) had sufficient documented contacts with health services to be fully vaccinated, but at least one immunization opportunity was missed. Multivariate analyses were conducted to identify factors associated with receipt of first dose diphtheria/pertussis/tetanus/oral polio vaccine (DPT/OPV) and with completion of the DPT/OPV series. Factors determining initiation of the series included maternal education (assessed by ability to speak French), household possession of a television, maternal age less than 35 years, child's birth in hospital, and, for non-French speakers, the mother considering vaccination to be affordable. Factors determining completion of the DPT/OPV series, among children who began vaccination, included maternal education, employment, and past positive experience with vaccination services (short waiting times, not having been turned away from vaccination, and not knowing a child with a post-vaccine 'abscess'). Vaccination coverage can be substantially increased in Conakry by improving health services to avoid missed opportunities, following the vaccination schedule correctly, reducing waiting times and avoiding abscesses.

Adult↗
PubMed1991

Age-specific differences in the relationship between oral contraceptive use and breast cancer.

Nearly all studies have suggested that the use of oral contraceptives (OC) is not associated with the aggregate risk of breast cancer diagnosed in women aged 20-54. Because of age-specific differences in the breast cancer-parity relationship and because of age-specific differences in other breast cancer risk factors, the Centers for Disease Control reexamined data from the Cancer and Steroid Hormone Study to assess whether OC use has different effects on the risk of breast cancer at different ages of diagnosis. This was a population-based case-control study conducted in eight geographic areas in the United States during 1980-1982. In these data, the relationship between the risk of breast cancer and OC use appeared to vary by age at diagnosis. Among women aged 20-34 years at diagnosis or interview, those who had ever used OC had a slightly increased risk of breast cancer (odds ratio 1.4, 95% confidence interval 1.0-2.1) when compared with women of the same ages who had never used OC. Among these women, there were no trends of increasing or decreasing risk with any measure of OC use. Among women aged 35-44 years, there was no association between OC use and breast cancer. Among women aged 45-54 years, those who used OC had a slightly decreased risk of breast cancer (odds ratio 0.9, 95% confidence interval 0.8-1.0). Among these women, the risk estimates decreased significantly with increasing time since first and last use. Although the slightly increased risk estimates for the youngest women are compatible with findings by other investigators, the decreased risk estimates for the oldest women have not been described in as many studies. Available data provide no reasons for changes in prescribing practices or in the use of OC as related to breast cancer risk.

Adult↗
PubMed1990

Estimation of risk ratios in case-base studies with competing risks.

The case-base study is a recently developed modification of the case-control design that leads to risk ratio estimates. Currently available methods for the analysis of case-base studies lead to estimates of the unconditional risk ratio which may be misleading of censoring occurs. In this manuscript, we describe an approach for the analysis of case-base studies that yields conditional risk ratio estimates which remain valid in the presence of censoring. The approach we propose for estimating risk ratios and their standard errors involves a non-iterative procedure.

Case-Control Studies↗
PubMed1990

A note on point estimation of the hazard ratio in exponential distributions.

The maximum likelihood estimator (MLE) of the ratio of the hazard rates in two exponential distributions is biased. This bias can be important when sample sizes are small or the ratio of these two hazard rates is large. When there is either no censoring or type II censoring, we propose using the uniformly minimum variance unbiased estimator (UMVUE). We show that using the UMVUE instead of the MLE reduces the mean-squared error (MSE). We have found that the UMVUE always has MSEs smaller than the MLE. We have also found that the UMVUE leads to important reductions in the MSE when the sample size used to calculate the hazard rate in the numerator of the hazard ratio is small (say less than or equal to 20) regardless of the sample size in the denominator. In the presence of type I censoring, the proposed estimator and the MLE are both biased. On the basis of a Monte Carlo study, however, we obtain similar reductions in the MSE using the UMVUE, as for no censoring or type II censoring.

Monte Carlo Method↗
PubMed1990

Estimating the number of suicides among Vietnam veterans.

Unconfirmed reports that 50,000 or more Vietnam veterans have committed suicide give the impression that these veterans are at exceedingly high risk of suicide compared with other veterans and nonveterans of the same age. On the basis of projections from two population-based mortality studies, the authors estimate that fewer than 9,000 suicides occurred among all Vietnam veterans from the time of discharge through the early 1980s. The sixfold or greater relative risk of suicide implied by the unsubstantiated suicide death tolls is also demonstrated to be incompatible with the findings of epidemiologic studies of mortality risk among Vietnam veterans.

Adult↗
PubMed1989

Estimating trends in the effectiveness of seat belts in saving lives, 1975-1985.

We examine the effectiveness of seat-belt systems for preventing mortality in automobile crashes. In particular, we examine whether seat-belt effectiveness has been constant over this period and conclude that there has been a trend toward an increased effectiveness of seat-belt systems. The relative odds of death associated with wearing seat belts dropped from 0.80 in 1975 to 0.34 in 1985. This trend results from improvements in both the type and design of seat belts and from additional design changes, such as padded dashboards and collapsible steering columns, that protect occupants at the time of collision.

Accidents, Traffic↗
PubMed1989

Actuarial analysis of a uniform and reliable preservation method for viable heart valve allografts.

CryoLife has developed a method for cryopreserving allograft heart valves for transplantation. Since 1984, 6,907 valves have been processed and 4,216 transplanted. Documentation was available on 2,647 transplants, 11 of which were removed for structural deterioration and 13, for nonstructural deterioration. At the end of 35 months, actuarial survival was 99.17% and the estimated freedom from reoperation, 97.16%. There have been no reports of thromboembolism or valve-related death.

Actuarial Analysis↗
PubMed1988

Salmonella typhimurium phage type 141 infections in Sheffield during 1984 and 1985: association with hens' eggs.

Food poisoning due to Salmonella typhimurium phage type 141 was unusual in the Sheffield area before 1984. The sudden increase in incidence of this phage type during 1984 and 1985, and its causative role in several small outbreaks in this period have been investigated. Epidemiological and laboratory investigations suggested that hens' eggs were the most likely source of S. typhimurium phage type 141.

Animals↗
PubMed1987

Monitoring for multiple malformations in the detection of epidemics of birth defects.

Although most known human teratogens often produce a combination of birth defects in an affected infant, surveillance programs aimed at detecting epidemics of birth defects usually only monitor rates of individual defects. A drawback to this approach is that an increase in the rate of infants affected with a specific combination of defects may lead to little or no increase in the rates of component defects. Using the Poisson distribution, we show that, compared with monitoring for individual defects, monitoring for combinations of two and three defects may require fewer numbers of births to detect an epidemic. In general, an increase can be detected more rapidly by monitoring the rates of defect combinations than by monitoring the rates of individual defects if most affected infants have combinations of defects rather than isolated defects. For example, in the case of Congenital rubella syndrome (CRS), monitoring for the combination of cataracts with deafness and/or patent ductus arteriosus could have led to earlier detection of an epidemic than could monitoring for cataracts alone. In contrast, in the case of thalidomide embryopathy, monitoring for reduction defects of upper limbs in combination with reduction defects of lower limbs and/or microtia/anotia would not have led to earlier detection of an epidemic than would monitoring for reduction defects of upper limbs alone. This is due mainly to the low frequency of defect combinations among affected cases. When used with regular monitoring for individual defects, surveillance of defect combinations can enhance the ability of monitoring programs to detect epidemics of birth defects.

Abnormalities, Drug-Induced↗