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Biomedical subjects

K C Chu

Publications and source records attributed to K C Chu.

At least 55 records · Page 3Linked to original sources
PubMed1994

Survival advantage differences by age. Evaluation of the extended follow-up of the Breast Cancer Detection Demonstration Project.

BACKGROUND: This study considers breast cancer survival patterns by age group among women diagnosed in the Breast Cancer Detection Demonstration Project (BCDDP) to provide insight into the nature of breast cancer and suggest a possible explanation as to why the results of the randomized clinical trials differ for women younger than 50 and those 50 or older. Based on the findings of several randomized clinical trials, there is a general consensus that breast cancer screening provides a significant benefit for women aged 50-69. From these trials, there is little evidence of a short term benefit and uncertainty regarding any long term benefit of mammographic screening for women aged 40-49. METHODS: The BCDDP was not a randomized trial, but a nationwide breast cancer screening program conducted between 1973-1980, in which all participants received annual physical and mammographic examinations. Using the BCDDP data, this study calculated 14-year breast cancer survival among 4051 women diagnosed with breast cancer between 1973 and 1980 and followed through 1988 and 1989. RESULTS: In all, 598 women died of breast cancer, resulting in an overall 14-year breast cancer survival of 83.4% (standard error = 0.007). Breast cancer survival varied by tumor type, lymph node status, tumor size, and stage at diagnosis. For most of the cases, however, both the distribution and breast cancer survival rates were similar for women aged 40-49, 50-59, and 60-69 across all prognostic indicators. Only breast cancer survival among women with invasive breast cancer who had a primary tumor 5 cm or larger or with positive lymph nodes differed by age, with women aged 60-69 at diagnosis having poorer survival. Analyses by modality of detection conducted in a subset of 2739 cases indicated that the 34.6% of the cases detected by mammography alone had the highest overall breast cancer survival rates (90.9%), while the 32.2% of the cases detectable by both physical examination and mammography had the lowest breast cancer survival (79.0%). Overall, women diagnosed with breast cancer in the BCDDP had a survival advantage if diagnosed with either a smaller tumor or no positive lymph nodes, or if their breast cancer was detected by mammography alone. For women with large tumors (> or = 5 cm), the survival was 80.8% for ages 40-49, 72.1% for ages 50-59, and 61.7% for ages 60-69. DISCUSSION: Due to the higher breast cancer survival rates among women aged 40-49 with poorer prognostic characteristics, the breast cancer survival advantage for having a smaller tumor, no positive lymph nodes, or breast cancer detected by mammography alone was lower for women aged 40-49 than women aged 50 or older at diagnosis. These differences in survival advantage may help to account for the differences in mortality by age in the randomized clinical trials.

Adult↗
PubMed1994

A method for partitioning cancer mortality trends by factors associated with diagnosis: an application to female breast cancer.

U.S. cancer mortality data derived from information recorded on death certificates are frequently relied upon as an indicator of progress against cancer. A limitation of this measure is the lack of information pertaining to the onset of disease, such as year-of-diagnosis, age-at-diagnosis, stage of disease at diagnosis and histology of lesions. However, population-based cancer registries collect these types of data and allow the calculation of an incidence-file based mortality rate. This incidence-based mortality rate allows a partitioning of mortality by variables associated with the cancer onset. Breast cancer incidence-based mortality measures are created and compared to mortality rates based on death certificates over a comparable time period. Novel mortality measures, such as mortality rates by stage-at-diagnosis, age-at-diagnosis and year-of-diagnosis, are used to illustrate the value of this approach.

Adult↗
PubMed1994

Cowden's disease: report of the first case in a Chinese.

A 19-year-old Chinese female presenting mucocutaneous manifestations including facial trichilemmomas, oral papillomatosis, and acral keratosis was diagnosed, according to the criteria proposed by Salem and Steck, as a definite case of Cowden's disease, although no members of her family were affected. The cutaneous reticulohistiocytic granuloma and congenital nystagmus of eyes that occurred in this case were new combinations in the syndrome. To the best of our knowledge, this is the first documented case of Cowden's disease in a Chinese.

Adult↗
PubMed1992

Implications of birth cohort patterns in interpreting trends in breast cancer rates.

BACKGROUND: Most investigations of trends in cancer rates are based on a cross-sectional approach, i.e., an examination of trends in rates by year of diagnosis or death. When there are longitudinal effects (i.e., trends in rates with successive birth cohorts), interpretation of cross-sectional trends can be misleading. Based on cross-sectional comparisons, U.S. breast cancer mortality rates have been reported to be decreasing over the last 20 years in younger women but to be increasing during the same period in older women. PURPOSE: To examine the impact of longitudinal effects on the divergence of cross-sectional trends in breast cancer mortality with age, we examined breast cancer mortality rates from 1969 to 1988 by birth cohort for White women in the United States. METHODS: By using a novel, nonparametric, permutational method to analyze 2-year, age-specific mortality rates for women aged 30-89 years, we identified trends in rates with successive birth cohorts. RESULTS: The divergence in trends with age is shown to be consistent with an increase in breast cancer risk with successive birth cohorts from 1900 to 1916 and with a decrease in breast cancer risk with successive birth cohorts beginning around 1926. CONCLUSION: Longitudinal effects have a significant impact on cross-sectional trends in breast cancer mortality. IMPLICATIONS: Continuation of the birth cohort trend in younger women, which could correspond to changes in reproductive patterns accompanying the "baby boom," would result in decreasing cross-sectional trends in women 60-69 years of age over the next decade and in women 70-79 years of age in the subsequent decade. Longitudinal effects must be taken into consideration when monitoring and evaluating the effects of early detection, treatment, and intervention programs using national rates.

Adult↗
PubMed1992

Pure rhabdomyosarcoma of the corpus uteri in a postpartum patient: report of a case and review of the literature.

Pure rhabdomyosarcomas originate in the female genital tract. They are uncommon and most often occur in infancy or childhood as sarcoma botryoides (embryonal rhabdomyosarcoma) which involve the vagina and cervix. Such tumors rarely occur in adults. A pure rhabdomyosarcoma of the uterus that arose in a postpartum patient is described. The pertinent literature is discussed.

Adult↗
PubMed1991

Analysis of the role of cancer prevention and control measures in reducing cancer mortality.

One goal of the war against cancer is to create declines in cancer mortality rates. A decrease in these rates can only occur in two ways: 1) a decrease in incidence rates and 2) a real increase in overall survival rates. Reductions in incidence rates can be envisioned to occur through three mechanisms (in order of the time course of cancer): 1) reduction or amelioration of environmental or lifestyle risk factors, 2) use of agents that prevent the occurrence of cancer by blocking the progression to cancer, and 3) early detection at a preneoplastic state combined with treatment that prevents or delays progression to invasive cancer. "True" increases in overall survival can occur by two mechanisms (in order of the time course of cancer): 1) early detection of cancer by screening tests and subsequent effective treatment and 2) advancements in treatment. Unique patterns or "fingerprints" of stage-specific incidence and overall incidence and of survival rates characterize the various cancer prevention and control mechanisms that can decrease mortality rates. The rates are presented for five organ sites that have shown reduced cancer mortality. The patterns of rates for breast cancer for women under the age of 65 years were most consistent with early detection. The testicular cancer fingerprints were most consistent with advances in treatment, whereas cervical cancer rates were most consistent with the detection of preneoplastic lesions. The stomach cancer fingerprints were indicative of reductions in lifestyle or environmental risks, and colorectal cancer rates were indicative of a combination of treatment advances and early detection. These fingerprint patterns can be extended to other situations in which mortality trends are changing in order to suggest possible causes of observed changes. Limitations of this model are also discussed.

Female↗
PubMed1991

Analysis of the temporal patterns of benefits in the Health Insurance Plan of Greater New York trial by stage and age.

Reductions in breast cancer mortality in the Health Insurance Plan of Greater New York trial are examined by age at entry and stage at diagnosis using a stage shift cancer screening model. The results indicate that for women aged 40-49 years at entry, benefits are associated with an internal stage shift of stage 1 cancers that have a prognosis poorer than the usual stage 1 cancers. Further, the results indicate that after 18 years of follow-up, of the reduction of 16 fewer deaths in the intervention group, 12-15 of the deaths are related to this internal shift. Given that stage 1 cases inherently have relatively good survival, the time required to see the screening benefit is substantial. For women aged 50-64 years at entry, the results suggest that benefits are associated primarily with shifts to or within stage 1. Further, the results indicate that after 6 years, of the reduction of 31 fewer deaths in the intervention group, 22 of the deaths are related to external shifts to stage 1. Given that stage 2 cancers have poorer survival than stage 1 cancers, screening benefit is seen sooner for the older cohort than for the younger cohort.

Adult↗
PubMed1990

National survey of the pattern of care for carcinoma of the lung.

A national survey of the patterns of care for carcinoma of the lung sponsored by the Commission on Cancer of the American College of Surgeons has documented continuing changes in epidemiology, treatment, and outcome. The project consisted of a long-term study of 15,219 patients whose diagnosis was made in 1981 and a short-term study of 19,074 patients whose diagnosis was made in 1986. The male/female incidence ratios have continued to decrease and the decrease has moved into the older age groups. Although the percentage of adenocarcinoma is increasing at the expense of squamous carcinoma, the latter is still the most prevalent histologic type. The accuracy of percutaneous needle biopsy and transbronchial biopsy of lung nodules reported from this group of 941 hospitals was high and equal to that reported by single institutions. The percentage of patients having a resection did not increase from 1981 to 1986, but for smaller lesions a move was apparent toward more lung-sparing resections. Little change has occurred in the use of adjuvant radiotherapy, particularly in stage III disease, where approximately 50% of the patients received postoperative irradiation. An improvement in the overall 5-year survival when compared with Surveillance, Epidemiology, and End Results data was noted. Whether this is a true improvement in survival or is the result of selection because of an unrecognized change in the pattern of care for patients with a carcinoma of the lung is unknown.

Adult↗
PubMed1989

Stage-shift cancer screening model.

A stage-shift cancer screening model is developed in the context of a randomized controlled trial (RCT) of cancer screening. In the model, detection by screening causes the time of diagnosis of the cancer to be advanced so that either the stage at diagnosis is shifted from one stage to the next lower one or the stage of diagnosis is unchanged but the cancer is diagnosed earlier in the stage. These are called external and internal stage shifts, respectively. At each stage the extent of the external and internal shifts and any associated mortality benefits are estimated. Further, the model allows the interrelationships of these benefits within and between stages to be delineated. This then allows us to better understand the results of the RCT. Data from a completed breast cancer screening RCT are used to illustrate the application of the model and its value in improving our understanding of the trial's results.

Adult↗
PubMed1989

Additive and multiplicative models and multistage carcinogenesis theory.

In light of the Armitage-Doll multistage carcinogenesis theory, this paper examines the assumption that an additive relative risk relationship is indicative of two carcinogens that affect the same stage in the cancer process. We present formulas to compute excess cancer risks for a variety of patterns for limited exposure durations to two carcinogens that affect the first and penultimate stages; and using an index of synergy proposed by Thomas (1982), we find a number of these patterns to produce additive, or nearly additive, relative risk relationships. The consistent feature of these patterns is that the two exposure periods are of short duration and occur close together.

Carcinogens, Environmental↗
PubMed1988

Analysis of breast cancer mortality and stage distribution by age for the Health Insurance Plan clinical trial.

The Health Insurance Plan (HIP) of Greater New York conducted a clinical trial to determine if screening for breast cancer with mammography and clinical examination would decrease breast cancer mortality. The extent of disease at diagnosis among breast cancers detected by screening and the effect of screening on breast cancer mortality have been evaluated in the cohort of all HIP women diagnosed with breast cancer within 6 years of entry into the trial and followed at least 18 years after trial entry. Six years was the earliest time at which the number of cases diagnosed in the control group was equal to the number of cases diagnosed in the study group. In the cohorts of women 40-49 and 50-64 years of age at entry, shifts were significant to lower stages for screen-detected cases. As a result, the study group women in each age cohort had significantly lower breast cancer mortality than control group women when statistical analyses were restricted to data from cases only. In the 40-49 age-at-entry cohort, the reduced breast cancer mortality in the study group appears to result from lower mortality in stage I cases as well as from earlier case detection, and this may explain differences between the two age-at-entry cohorts in the length of follow-up time required to demonstrate a mortality reduction due to screening.

Adult↗
PubMed1987

A nonmathematical view of mathematical models for cancer.

A qualitative view of mathematical models for cancer is presented. The Armitage and Doll multistage and Moolgavkar two-stage models of cancer are discussed in terms of their physical models. Time-related factors for these models as well as some of their characteristics are presented. The effect of age at first exposure, duration of exposure, time since last exposure and stage of carcinogenic effect on risk are detailed.

Age Factors↗
PubMed1987

Use of multistage models to infer stage affected by carcinogenic exposure: example of lung cancer and cigarette smoking.

Statistical methods based on the Armitage-Doll mathematical model of the carcinogenic process are presented for analyzing epidemiologic case-control studies of cancer. These methods are proposed to provide inferences regarding the stage(s) in the cancer process at which the exposure of interest acts. An example of these methods is given which shows evidence that carcinogens in cigarette smoke appear to affect the transition rates for two separate stages in the development of lung cancer, and the relative magnitudes of these effects are estimated. The data for this analysis came from a European multi-center case-control study of lung cancer. The results of the analysis show that: (1) the relative risk of lung cancer among continuing smokers compared to nonsmokers of the same age decreases as the age started smoking increases, while the rate of smoking stays fixed, a result which indicates a carcinogenic effect on an early stage in the process; and (2) the relative risk among ex-smokers compared to continuing smokers having the same duration and rate of smoking decreases with time since smoking stopped, a result which indicates a carcinogenic effect on a late stage in the process. Both results are shown to be best described by the hypothesis that cigarette smoking affects two stages. The estimated relative magnitudes of cigarettes' carcinogenic effects on the two stages indicate that the largest proportion of the total lifetime lung cancer risk among continuing smokers is due to its late stage effect, and that the proportion of risk due to causes other than smoking varies from 23% among men smoking 1-10 cigarettes per day to 6% among those smoking greater than 30 cigarettes per day. These findings imply that preventive measures directed toward inducing smokers to stop would have a potentially substantial payoff in reducing future lung cancer mortality.

Age Factors↗
PubMed1987

Differentiating among proposed mechanisms for tumor promotion in mouse skin with the use of the multievent model for cancer.

Numerous mechanisms for tumor promotion in mouse skin have been recently proposed. These include the multistage, genetic view of Slaga, Furstenberger, and Marks; the multistage, genetic and/or epigenetic view of Parkinson; and the two-stage view of Yuspa and Hennings. With the use of the multievent model, a mathematical model for cancer that can incorporate cell proliferation phenomena, these tumor promotion mechanisms were modeled mathematically. It was found that the models had different predictions about the incidence of papillomas in initiator-promoter-initiator experiments and the incidence of carcinomas in initiator-promoter experiments with varying periods of tumor promotion. Upon analysis, existing data were shown to be in agreement with the Yuspa and Hennings two-stage model. The analysis also supported the view, formulated by Scribner and co-workers, that different types of initiated cells were created, some capable of transformation to carcinomas and some not. Phenomena determined by use of benign tumors as the end point may need to be demonstrated with the use of the carcinoma as the end point, prior to the acceptance of these phenomena being applicable to the human carcinogenic process.

4-Nitroquinoline-1-oxide↗
PubMed1985

Coxsackievirus B4 infection of sympathetic ganglia in squirrel monkeys.

Lumbar sympathetic ganglionitis was found by light microscopy in 2 of 17 (12%) squirrel monkeys (Saimiri sciureus) experimentally infected with Coxsackievirus B4. This finding shows that viruses can cause ganglionitis which, in turn, must cause autonomic nervous system dysfunction. Such viral ganglionitis may explain some diseases, including cardiovascular ones, of poorly understood or unknown etiology which present with manifestations of dysfunction of the sympathetic nervous system.

Animals↗