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Biomedical subjects

M Berwick

Publications and source records attributed to M Berwick.

At least 19 recordsLinked to original sources
PubMed2004

A note on competing risks in survival data analysis.

Survival analysis encompasses investigation of time to event data. In most clinical studies, estimating the cumulative incidence function (or the probability of experiencing an event by a given time) is of primary interest. When the data consist of patients who experience an event and censored individuals, a nonparametric estimate of the cumulative incidence can be obtained using the Kaplan-Meier method. Under this approach, the censoring mechanism is assumed to be noninformative. In other words, the survival time of an individual (or the time at which a subject experiences an event) is assumed to be independent of a mechanism that would cause the patient to be censored. Often times, a patient may experience an event other than the one of interest which alters the probability of experiencing the event of interest. Such events are known as competing risk events. In this setting, it would often be of interest to calculate the cumulative incidence of a specific event of interest. Any subject who does not experience the event of interest can be treated as censored. However, a patient experiencing a competing risk event is censored in an informative manner. Hence, the Kaplan-Meier estimation procedure may not be directly applicable. The cumulative incidence function for an event of interest must be calculated by appropriately accounting for the presence of competing risk events. In this paper, we illustrate nonparametric estimation of the cumulative incidence function for an event of interest in the presence of competing risk events using two published data sets. We compare the resulting estimates with those obtained using the Kaplan-Meier approach to demonstrate the importance of appropriately estimating the cumulative incidence of an event of interest in the presence of competing risk events.

Humans↗
PubMed2004

Estimating the relative risk of developing melanoma in INK4A carriers.

Estimation of the relative risk of cancer due to rare germline mutations using population-based epidemiological techniques is challenging, since studies with very large numbers of subjects are required. In this pilot study using a novel study design, we evaluated the role of INK4A mutations in melanoma by comparing patients with multiple primary melanomas to those with single primaries. Patients were ascertained from the Surgery and Dermatology Clinics at Memorial Sloan-Kettering Cancer Center and at the Yale University Pigmented Lesion Clinic. Subjects completed a questionnaire covering risk factors for melanoma and were tested for INK4A mutations. Five (8%) of 65 patients with multiple primaries had a mutation, compared with none of 88 patients with single primaries (P=0.03). Examination of other factors, such as number of nevi on the arms of the patients, fair skin, hair and eye colour, and other phenotypic characteristics associated with the risk of melanoma, demonstrates that these factors exhibit higher prevalence in the multiple primary cases than in the single primaries. These results provide evidence of the utility of the new study design in evaluating the impact of rare but highly penetrant cancer risk factors.

Adolescent↗
PubMed2002

Randomized, placebo-controlled trial of dietary supplementation of alpha-tocopherol on mutagen sensitivity levels in melanoma patients: a pilot trial.

We evaluated the effects of vitamin E (dl-alpha-tocopherol) on mutagen sensitivity levels in a randomized placebo-controlled pilot trial. In brief, a dietary supplement of 1000 mg/day vitamin E or a placebo was randomly administered for 3 months to melanoma outpatients clinically free of the disease. Plasma vitamin E and mutagen sensitivity levels were measured at baseline and at the end of the trial after 3 months. At baseline, we found no significant differences in plasma vitamin E and mutagen sensitivity levels between the two groups. We also measured dietary intake at baseline and found dietary vitamin E to be a poor predictor of plasma levels of vitamin E. After 3 months of supplementation, we found that plasma levels of alpha-tocopherol increased significantly (P = 0.0005) in the vitamin E compared to the placebo group. We also found a non-significant, but consistent decrease in plasma gamma-tocopherol concentrations in the vitamin E supplemented compared to the placebo group. We did not find any significant difference between the vitamin E and placebo groups in mutagen sensitivity levels either at baseline or after 3 months of supplementation. We conclude that short term vitamin E supplementation, although it causes increased blood levels of alpha-tocopherol, does not provide protection against bleomycin-induced chromosome damage.

Adult↗
PubMed2001

Mutagen sensitivity as an indicator of soft tissue sarcoma risk.

The etiology of soft tissue sarcoma is poorly understood. Exposure to environmental chemicals may play a role, but the data are not clear. We compared a group of soft tissue sarcoma patients with healthy controls to determine whether the mutagen sensitivity assay, a simple chromosome aberration assay using the radiomimetic bleomycin, might be useful to identify patients at risk for soft tissue sarcoma. Patients with a diagnosis of soft tissue sarcoma at Memorial Sloan-Kettering's outpatient clinic signed informed consent and donated 30 ml of blood. Controls were selected from the general population of Connecticut by random digit dialing. Unrepaired DNA damage was assessed for 100 metaphase spreads for each individual, with the number of breaks in chromatids being counted as breaks per cell (b/c). The 20 cases with soft tissue sarcoma had 1.03 mean b/c and the controls had 0.88 b/c (P = 0.16). Patients with soft tissue sarcoma were 5.7 times more likely to be mutagen sensitive than controls (P = 0.01), as determined after dividing subjects into sensitive or not sensitive groups based on the median b/c among controls. As mutagen sensitivity has been shown to be associated with a number of cancers and appears to reflect genetic susceptibility, this assay may be an appropriate biomarker for radiation sensitivity or it may be a marker of susceptibility to soft tissue sarcoma. Larger studies should be undertaken to assess these possibilities.

Adult↗
PubMed2001

Double-strand breaks and tumorigenesis.

The establishment of connections between biochemical defects and clinical disease is a major goal of modern molecular genetics. In this review, we examine the current literature that relates defects in the two major DNA double-strand-break repair pathways--homologous recombination and nonhomologous end-joining--with the development of human tumors. Although definitive proof has yet to be obtained, the current literature is highly suggestive of such a link.

Animals↗
PubMed2001

Validation of denaturing high performance liquid chromatography as a rapid detection method for the identification of human INK4A gene mutations.

The incidence of melanoma is increasing rapidly in western countries. Genetic predisposition in familial and in some sporadic melanomas has been associated with the presence of INK4A gene mutations. To better define the risk for developing sporadic melanoma based on genetic and environmental interactions, large groups of cases need to be studied. Mutational analysis of genes lacking hot spots for sequence variations is time consuming and expensive. In this study we present the application of denaturing high performance liquid chromatography (DHPLC) for screening of mutations. Exons 1alpha, 2, and 3 were amplified from 129 samples and 13 known mutants, yielding 347 products that were examined at different temperatures. Forty-two of these amplicons showed a distinct non-wild-type profile on the chromatogram. Independent sequencing analysis confirmed 16 different nucleotide variations in Leu32Pro; Ile49Thr; 88 del G; Gln50Arg; Arg24Pro; Met53Ile; Met53Thr; Arg58stop; Pro81Leu; Asp84Ala; Arg80stop; Gly101Trp; Val106Val; Ala148Thr; and in positions (-2) in intron 1 (C --> T); and in the 3' UTR, nucleotide 500 (C --> G). No false negatives or false positives were obtained by DHPLC in samples with mutations or polymorphisms. We conclude that the DHPLC is a fast, sensitive, cost-efficient, and reliable method for the scanning of INK4A somatic or germline mutations and polymorphisms of large number of samples.

Buffers↗
PubMed2001

Ultraviolet A and melanoma: a review.

The incidence and mortality rates of melanoma have risen for many decades in the United States. Increased exposure to ultraviolet (UV) radiation is generally considered to be responsible. Sunburns, a measure of excess sun exposure, have been identified as a risk factor for the development of melanoma. Because sunburns are primarily due to UVB (280-320 nm) radiation, UVB has been implicated as a potential contributing factor to the pathogenesis of melanoma. The adverse role of UVA (320-400 nm) in this regard is less well studied, and currently there is a great deal of controversy regarding the relationship between UVA exposure and the development of melanoma. This article reviews evidence in the English-language literature that surrounds the controversy concerning a possible role for UVA in the origin of melanoma. Our search found that UVA causes DNA damage via photosensitized reactions that result in the production of oxygen radical species. UVA can induce mutations in various cultured cell lines. Furthermore, in two animal models, the hybrid Xiphophorus fish and the opossum (Mondelphis domestica), melanomas and melanoma precursors can be induced with UVA. UVA radiation has been reported to produce immunosuppression in laboratory animals and in humans. Some epidemiologic studies have reported an increase in melanomas in users of sunbeds and sunscreens and in patients exposed to psoralen and UVA (PUVA) therapy. There is basic scientific evidence of the harmful effects of UVA on DNA, cells and animals. Collectively, these data suggest a potential role for UVA in the pathogenesis of melanoma. To date evidence from epidemiologic studies and clinical observations are inconclusive but seem to be consistent with this hypothesis. Additional research on the possible role of UVA in the pathogenesis of melanoma is required.

Animals↗
PubMed2001

Histologic classification of tumor-infiltrating lymphocytes in primary cutaneous malignant melanoma. A study of interobserver agreement.

The density and distribution of lymphocytes infiltrating the vertical growth phase of primary cutaneous melanomas has been suggested by several studies to be of prognostic significance. However, few pathologists comment on tumor-infiltrating lymphocytes (TILs), and there is the perception that the assessment of TILs is subject to great interobserver variability. We studied interobserver agreement on the categorization of TILs; 20 cases of primary cutaneous malignant melanoma with a vertical growth phase component were circulated among 3 pathologists and 3 dermatologists. For each case, TILs were classified as brisk, nonbrisk, or absent according to Clark. Only 1 pathologist (a dermatopathologist) was familiar with the classification of TILs. Observers were given written guidelines and a brief tutorial before their examination of the slides. Our results show that with little instruction, overall agreement among observers was good (kappa values, 0.6 or more), especially among pathologists (kappa values, > 0.7). Three observers had excellent agreement among each other (kappa values, > 0.75). These findings suggest that the categorization of TILs can be easily taught and can be applied with an acceptable level of reproducibility in routine diagnostic practice.

Humans↗
PubMed2001

Issues in the epidemiology of melanoma.

Cutaneous melanoma is a significant health problem throughout the developing world. Primary and secondary prevention are discussed. The wavelengths of the ultraviolet radiation spectrum and their association with melanoma are discussed. Although excessive sun exposure during childhood is a critical risk factor, excessive sun exposure during adult years is also important. The major risk factors for melanoma--numerous or atypical moles and a sun-sensitive phenotype--are genetic. Their interaction with sun exposure is currently being examined, as well as the interaction of other genetic factors, such as alterations in the melanocortin receptor and the familial melanoma gene, INK4A. Secondary prevention strategies include self-examination and physician examination. New technologies are being developed to supplement visual examination of suspected lesions. These technologies are discussed in detail and include digital photography, digital dermoscopy, confocal scanning laser microscopy and automated diagnosis systems.

Humans↗
PubMed2000

Patterns of detection in patients with cutaneous melanoma.

BACKGROUND: Despite the importance of early detection in preventing mortality from melanoma, little is known regarding how patients with the disease come to diagnosis. METHODS: The authors prospectively evaluated 471 newly diagnosed melanoma patients between 1995 and 1998. Patients completed a questionnaire that included 1) identification of the person who detected the lesion, 2) the anatomic location of the lesion, and 3) family history of melanoma. Logistic regression analysis was performed to examine the relation between detection patterns and lesion thickness, adjusting for age, gender, anatomic site of the primary lesion, and family history of melanoma. RESULTS: The majority of patients detected their own melanoma (n = 270; 57%). Females were more likely to self-detect than males (69% vs. 47%; P < 0.0001). Physicians detected the melanoma in 16% of patients (n = 74), followed by "spouse" in 11% of patients (n = 51). Within this group, detection by wives was 7.5 times more common than detection by husbands (P < 0.0001). Logistic regression analysis revealed that physicians were 3.6 times more likely to detect thin lesions (</=0.75 mm) compared with nonphysician detectors (95% confidence interval [95% CI], 2.1, 6.5; P = 0.0001). In addition, patients who reported a family history of melanoma had a 2.7-fold increased likelihood of presenting with a thin lesion (95% CI, 1.6, 4.7; P = 0.0003). CONCLUSIONS: Physician detection and a report of a family history of melanoma are associated with the presentation of patients with early melanoma, suggesting that awareness of the disease among physicians and the public is critical for preventing mortality from melanoma. Increasing melanoma awareness in males may be a particularly effective means of secondary prevention.

Adult↗
PubMed2000

Markers of DNA repair and susceptibility to cancer in humans: an epidemiologic review.

DNA repair is a system of defenses designed to protect the integrity of the genome. Deficiencies in this system likely lead to the development of cancer. The epidemiology of DNA repair capacity and of its effect on cancer susceptibility in humans is, therefore, an important area of investigation. We have summarized all of the published epidemiologic studies on DNA repair in human cancer through 1998 (n = 64) that addressed the association of cancer susceptibility with a putative defect in DNA repair capacity. We have considered study design, subject characteristics, potential biases, confounding variables, and sources of technical variability. Assays of DNA repair capacity used, to date, can be broadly grouped into five categories: 1) tests based on DNA damage induced with chemicals or physical agents, such as the mutagen sensitivity assay, the G(2)-radiation assay, induced micronuclei, and the Comet assay; 2) indirect tests of DNA repair, such as unscheduled DNA synthesis; 3) tests based on more direct measures of repair kinetics, such as the host cell reactivation assay; 4) measures of genetic variation associated with DNA repair; and 5) combinations of more than one category of assay. The use of such tests in human populations yielded positive and consistent associations between DNA repair capacity and cancer occurrence (with odds ratios in the range of 1. 4-75.3, with the majority of values between 2 and 10). However, the studies that we have reviewed have limitations, including small sample size, "convenience" controls, the use of cells different from the target organ, and the use of mutagens that do not occur in the natural environment. The evolving ability to study polymorphisms in DNA repair genes may contribute to new understandings about the mechanisms of DNA repair and the way in which DNA repair capacity affects the development of cancer.

Biomarkers, Tumor↗
PubMed2000

Signs and symptoms of melanoma in older populations.

We conducted a descriptive study to assess the relationship between increasing age and the reporting of melanoma signs/symptoms in 634 hospital-based and 624 population-based incident cases of melanoma. Multivariate logistic regression was used to evaluate the relationship between older age (> or = 50 years) and the reporting of melanoma signs/symptoms. Older patients were less likely to report itching and change in elevation of their lesions (P < 0.05). Change in color was also less likely to be reported by older patients, although not statistically significant. Ulceration of the lesion was reported significantly more by older patients (P < 0.05). Older individuals may be less likely to report itching and change in elevation/color of their lesions, but more likely to report ulceration, a symptom associated with advanced disease and poor prognosis. Further research is necessary to provide a better understanding of the development of melanoma in older populations so that new strategies can be explored to improve early detection in this age group.

Adult↗
PubMed2000

Immunoreactivity with the anti-MAGE antibody 57B in malignant melanoma: frequency of expression and correlation with prognostic parameters.

The melanoma-associated antigen (MAGE) family consists of a number of antigens initially recognized by cytotoxic T lymphocytes, which are currently being investigated for immunotherapy of patients with metastatic melanoma and other tumor types. Expression of MAGE mRNA in melanocytic tumors is said to be restricted to invasive malignant tumors and absent in nevi. Recently, a monoclonal antibody (57B) has become available to examine MAGE protein expression in archival material. In this study, we performed immunohistochemical analysis on 132 melanocytic nevi and 205 melanomas (85 primary cutaneous melanomas and 120 metastatic tumors) to determine the frequency of MAGE expression and to explore a potential correlation with various prognostic parameters. None of the melanocytic nevi and none of the 20 in situ melanomas was immunopositive with the antibody 57B. Immunoreactivity was present in 17 of 65 (26%) primary invasive melanomas of the skin and in 30 of 120 (25%) metastatic tumors. Positive immunostaining did not correlate with tumor stage (P = .66), Breslow thickness (P = .39), Clark level (P = .5), or the histologic type of melanoma (P = .23) but was associated with a brisk infiltrate of lymphocytes involving the vertical growth phase of melanomas (P = .01). Because tumor-infiltrating lymphocytes in melanoma are associated with longer survival, our findings suggest a potential prognostic role for MAGE. Furthermore, the seeming restriction of immunopositivity to invasive malignant tumors suggests a potential diagnostic role for the antibody 57B in confirming the malignant potential of a melanocytic tumor.

Animals↗
PubMed2000

A pilot study using nurse education as an intervention to increase skin self-examination for melanoma.

BACKGROUND: A pilot study of an intervention using nurse education for skin self-examination (SSE) was conducted in order to determine specific factors that would be important for the design of a larger intervention. METHODS: Seventy-five subjects completed a pretest, a posttest, a thorough skin examination by a dermatologist, and an educational session by a nurse. RESULTS: Results showed that the subjects increased the frequency of SSE to a predetermined optimal frequency of once every one to two months. Increases in optimal SSE were associated with increases in knowledge about melanoma (p = 0.006). CONCLUSIONS: Before intensive campaigns are launched to improve SSE, models incorporating theories of behavioral change should be tested.

Adolescent↗
PubMed2000

Occupational exposure to formaldehyde and wood dust and nasopharyngeal carcinoma.

OBJECTIVES: To investigate whether occupational exposures to formaldehyde and wood dust increase the risk of nasopharyngeal cancer (NPC). METHODS: A multicentered, population based case-control study was carried out at five cancer registries in the United States participating in the National Cancer Institute's SEER program. Cases (n=196) with a newly diagnosed NPC between 1987 and 1993, and controls (n=244) selected over the same period from the general population through random digit dialing participated in structured telephone interviews which inquired about suspected risk factors for the disease, including a lifetime history of occupational and chemical exposure. Histological type of cancer was abstracted from clinical records of the registries. Potential exposure to formaldehyde and wood dust was assessed on a job by job basis by experienced industrial hygienists who were blinded as to case or control status. RESULTS: For formaldehyde, after adjusting for cigarette use, race, and other risk factors, a trend of increasing risk of squamous and unspecified epithelial carcinomas was found for increasing duration (p=0.014) and cumulative exposure (p=0.033) but not for maximum exposure concentration. The odds ratio (OR) for people cumulatively exposed to >1.10 ppm-years was 3.0 (95% confidence interval (95% CI) 1.3 to 6.6) compared with those considered unexposed. In analyses limited to jobs considered definitely exposed, these trends became stronger. The associations were most evident among cigarette smokers. By contrast, there was no association between potential exposure to formaldehyde and undifferentiated and non-keratinising carcinomas. There was little evidence that exposure to wood dust increased risk of NPC, as modest crude associations essentially disappeared after control for potential exposure to formaldehyde. CONCLUSIONS: These results support the hypothesis that occupational exposure to formaldehyde, but not wood dust, increases risk of NPC. This association seems to be specific to squamous cell carcinomas. Established cohorts of workers exposed to formaldehyde and wood dust should continue to be monitored for NPC and other respiratory cancers. Future studies of NPC should take into account histological type in assessing risk from environmental and host factors.

Adolescent↗