Search PubMed⌕ Search

Biomedical subjects

R K Severson

Publications and source records attributed to R K Severson.

At least 37 records · Page 2Linked to original sources
PubMed1997

Residential exposure to magnetic fields and acute lymphoblastic leukemia in children.

BACKGROUND: Previous studies found associations between childhood leukemia and surrogate indicators of exposure to magnetic fields (the power-line classification since known as "wire coding"), but not between childhood leukemia and measurements of 60-Hz residential magnetic fields. METHODS: We enrolled 638 children with acute lymphoblastic leukemia (ALL) who were under 15 years of age and were registered with the Children's Cancer Group and 620 controls in a study of residential exposure to magnetic fields generated by nearby power lines. In the subjects' current and former homes, data collectors measured magnetic fields for 24 hours in the child's bedroom and for 30 seconds in three or four other rooms and outside the front door. A computer algorithm assigned wire-code categories; based on the distance and configuration of nearby power lines, to the subjects' main residences (for 416 case patients and 416 controls) and to those where the family had lived during the mother's pregnancy with the subject (for 230 case patients and 230 controls). RESULTS: The risk of childhood ALL was not linked to summary time-weighted average residential magnetic-field levels, categorized according to a priori criteria. The odds ratio for ALL was 1.24 (95 percent confidence interval, 0.86 to 1.79) at exposures of 0.200 mu T or greater as compared with less than 0.065 mu T. The risk of ALL was not increased among children whose main residences were in the highest wire-code category (odds ratio as compared with the lowest category, 0.88; 95 percent confidence interval, 0.48 to 1.63). Furthermore, the risk was not significantly associated with either residential magnetic-field levels or the wire codes of the homes mothers resided in when pregnant with the subjects. CONCLUSIONS: Our results provide little evidence that living in homes characterized by high measured time-weighted average magnetic-field levels or by the highest wire-code category increases the risk of ALL in children.

Case-Control Studies↗
PubMed1997

The age peak in childhood acute lymphoblastic leukemia: exploring the potential relationship with socioeconomic status.

BACKGROUND: White children have a much higher incidence rate of acute lymphoblastic leukemia (ALL) than do African American children. This discrepancy, coupled with the geographic and temporal variations in the incidence of childhood ALL, have led to speculation that factors associated with socioeconomic status (SES) may play an important role in its etiology. Because most of the variation is accounted for by the occurrence of a peak in incidence between the ages of 2 and 5 years, the purpose of this study was to compare the SES of children diagnosed with ALL between the peak ages of 2-5 years with those children diagnosed at other ages (birth-1 year and 6-14 years). METHODS: Patients included 4210 children who were diagnosed with ALL between January 1, 1989 and December 31, 1991 by a member institution of the Children's Cancer Group or the Pediatric Oncology Group. Of these children, 3614 were white and 596 were African American. The SES of a case was defined as the SES of the child's zip code of residence at the time of diagnosis. Five sociodemographic variable categories for each zip code were obtained from the 1990 U.S. Census including per capita income, number of housing units by household income, number of housing units by level of urbanization, number of persons older than 25 years by educational attainment, and number of persons by occupation. Mean values were compared for white children versus African American children, and peak ages (2-5 years) versus nonpeak ages (birth-1 year and 6-14 years) for both whites and African Americans. In addition, Wilcoxon's rank sum tests were performed. RESULTS: There were statistically significant differences between the means in each of the socioeconomic categories when African Americans were compared with whites. However, within race, the means of the SES variables for white children diagnosed during the peak ages (2-5 years) were not significantly different from children diagnosed at other ages (birth-1 year and 6-14 years). Similarly, all but one of the comparisons for African American children yielded nonstatistically significant results. Similar results were obtained from the Wilcoxon's rank sum tests. CONCLUSIONS: The results of this analysis suggest that age differences in childhood ALL incidence may not be solely accounted for by SES differences.

Adolescent↗
PubMed1997

Incidence of colorectal adenocarcinoma by anatomic subsite. An epidemiologic study of time trends and racial differences in the Detroit, Michigan area.

BACKGROUND: Colorectal adenocarcinoma may represent more than one disease process. Numerous epidemiologic studies suggest that rates of occurrence of colorectal adenocarcinoma at particular anatomic subsites (e.g., right colon, left colon, and rectum) may be associated with distinctive geographic, demographic, and risk factor profiles. This study explored time trends over a 22-year period of the incidence of adenocarcinoma of the colon and rectum at various subsites among patients of different race, gender, and stage of disease. METHODS: Data on the incidence of colorectal adenocarcinoma were obtained from a population-based cancer registry in the Detroit, Michigan area funded by the National Cancer Institute. Age-adjusted incidence rates were analyzed by year of diagnosis. Relative survival rates were also obtained for different race and gender categories, along with disease stage at diagnosis. RESULTS: A major rise was revealed in the incidence of adenocarcinoma in the right colon among African American men and women between the mid-1970s and the early 1980s. The rise was greatest among African American men and accounts for increases in late stage disease among them. Corresponding decreases in survival among African American men were noted. CONCLUSIONS: These findings indicated widely differing disease patterns based on anatomic subsite and patient demography and also indicated a need for targeted efforts at early detection of adenocarcinoma of the right colon among African Americans.

Adenocarcinoma↗
PubMed1997

Racial differences in breast cancer survival: the interaction of socioeconomic status and tumor biology.

OBJECTIVE: Our purpose was to evaluate the effect of sociodemographic and clinical variables on survival rates of African-American and white women with breast cancer. STUDY DESIGN: Between 1988 and 1992 the Metropolitan Detroit Cancer Surveillance System Identified 10,502 women (82% white and 18% African-American) in whom invasive breast cancer was diagnosed. Cox proportional hazards regression was used to estimate the relative risk of death for African-Americans compared with whites after controlling for variables believed to influence survival. RESULTS: African-American women were more likely than white women to have tumors that were of a more advanced stage, a higher grade, and hormone receptor-negative. After controlling for age, tumor size, stage, histologic grade, census-derived socioeconomic status, and the presence of a residency training program at the treatment hospital, the relative risk of dying for African-Americans compared with whites was 1.68 (95% confidence interval, 1.27-2.23) for women less than 50 years of age, and 1.33 (95% confidence interval, 1.13-1.56) for women older than 50 years of age. CONCLUSIONS: Known factors that predict survival differences between African-Americans and whites are more prevalent among women less than 50 years of age, emphasizing the need to focus more attention on public health efforts directed toward younger women.

Adolescent↗
PubMed1997

National cancer clinical trials: children have equal access; adolescents do not.

PURPOSE: To determine whether adolescents with cancer, who in comparison to younger patients have a higher cancer incidence and lower mortality reduction, have equal access to national cancer clinical trials. METHODS: The ethnic/racial distribution of 29,859 subjects < 20 years of age entered onto National Cancer Institute-sponsored clinical trials between January 1, 1991, and June 30, 1994, was compared with the expected distribution of patients of the same age in the United States. RESULTS: The Children's Cancer Group and Pediatric Oncology Group had 29,134 (97.6%) of the total study entries among < 20-year-old subjects during the 3.5 years of surveillance. The adult cooperative groups accounted for < 3% of the clinical trials entries in the 15-19-year age range. When analyzed nationally by region, the under-representation of the older adolescent subjects was universal. From other analyses, the two pediatric cooperative groups were estimated to have registered > 94% of the children < 15 years of age who were expected to have been diagnosed to have cancer, but only 21% of the cancer patients in the 15-19-year age group. CONCLUSIONS: The national pediatric cancer cooperative groups allow the majority of American children < 15 years of age and their families equal opportunity to access clinical cancer trials, regardless of race or ethnicity. Among patients 15-19 years of age, however, > 75% are not being enrolled by any cooperative group sponsored by the National Cancer Institute. Thus, older adolescents are disadvantaged with respect to access to the national clinical trials, regardless of their race or ethnicity.

Adolescent↗
PubMed1997

Seasonal trends in the self-detection of breast cancer: indications from the Cancer and Steroid Hormone (CASH) study.

Of 2895 women who self-detected an incident breast cancer that required surgery, peaks in month of detection occurred in spring and late autumn (p = 0.012). For the subset of cases for whom receptor status was available, there was a highly significant seasonal variation in detection only for those with ER-negative tumors. Further investigations into seasonality and breast cancer detection may be warranted.

Adult↗
PubMed1997

Magnetic field exposure assessment in a case-control study of childhood leukemia.

Epidemiologic evaluation of the relation between magnetic field exposures and cancer depends critically on study design, particularly the methods used for exposure assessment. We incorporated a complex magnetic field exposure assessment protocol into a large incident case-control study of childhood leukemia. We measured residential magnetic fields using a standard protocol in current and former homes of 638 cases and 620 controls and determined wire codes for 414 case-control pairs. We chose a time-weighted average of magnetic field measurements in each eligible home, weighted by the time the subject lived in each home as the main exposure metric for each subject. We found that 24-hour bedroom magnetic field measurements adequately characterize children's residential exposure and that measuring other rooms contributes only slightly to the estimate of average residential exposure to magnetic fields. Front door measured fields provide useful exposure information when interior measurements are missing. If feasible, measuring multiple homes in which the subject has resided is preferable to measuring a single home. A similar distribution of wire codes for controls agreeing or refusing to participate in our study implies that risk estimates derived from wire code data will not be influenced by response bias.

Adolescent↗
PubMed1996

Trends in the stage specific incidence of prostate carcinoma in the Detroit metropolitan area, 1973-1994.

BACKGROUND: Much of the recent increase in prostate carcinoma incidence has been attributed to screening with prostate specific antigen (PSA). Controversy exists as to whether this screening will ultimately impact prostate carcinoma mortality. Until adequate time elapses since PSA screening became widespread, or a randomized trial of PSA screening is completed, the effect of PSA screening on prostate carcinoma mortality cannot be determined. In the interim, stage specific prostate carcinoma incidence rates may provide an indication of the effect of PSA screening. METHODS: Annual stage specific age-adjusted prostate carcinoma incidence rates for the years 1973 through 1994 were obtained from the Metropolitan Detroit Cancer Surveillance System (MDCSS), a member of the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) Program. These incidence rates were analyzed for trends using Poisson regression analysis. RESULTS: There were 10,801 cases of prostate carcinoma in black men and 31,501 in white men during the 22-year period. Incidence rates for stages of local and regional prostate carcinoma reached a maximum in 1992 and 1993. Distant stage prostate carcinoma incidence has steadily declined since 1989 (P < 0.001), the year in which the increasing trend in the incidence rates for local and regional stage prostate carcinoma were first noted. CONCLUSIONS: These findings suggest that a substantial proportion of early stage prostate carcinoma detected by PSA is in fact clinically important and that early detection of these carcinomas has resulted in a continuous decline in the stage of metastatic prostate carcinoma since 1989.

Age Factors↗
PubMed1996

Trends in cancer incidence among children in the U.S.

BACKGROUND: This report provides results of an analysis of temporal trends in childhood cancer incidence in the U.S. stratfied by age, sex, and to a lessor extent, race, within common histologic subtypes. METHODS: Population-based data from nine registries of the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute were analyzed. The analysis was limited to children age < or = 14 years. Cancer cases were restricted to those patients with a malignant neoplasm diagnosed between 1974 and 1991; more than 12,000 children were included. Average annual percentage change in incidence rates and corresponding 95% confidence intervals were estimated from the maximum likelihood method of Poisson regression. RESULTS: Among children age < or = 14 years there was a 1% average yearly increase (95% CI 0.6, 1.3) in the incidence rates of all malignant neoplasms combined. The average annual percentage change was similar for males and females, and slightly higher for black children compared with white children. Rates increased an average of 2% or more per year for astroglial tumors, rhabdomyosarcomas, germ cell tumors, and osteosarcomas. The average annual percentage change for acute lymphoid leukemia was 1.6% and trends were somewhat stronger for blacks than whites. Cancer trends, in general, were strongest in young children. In particular, increases in astroglial tumors and rhabdomyosarcomas were most apparent among children age < 3 years, and for retinoblastoma and neuroblastoma among children in their first year of life. The average annual percentage change for acute lymphoid leukemia did not vary dramatically with age, however children age < 2 years had stronger trends compared with older children. We found little evidence for increasing trends in Wilms' tumor, primitive neuroectodermal tumors, or hematopoietic neoplasms other than acute lymphoid leukemia. CONCLUSIONS: These results suggest that cancer occurrence among children within specific histologies increased modestly in the U.S. between 1974 and 1991, and that the increases were most apparent among young children.

Adolescent↗
PubMed1996

Racial differences in survival of female breast cancer in the Detroit metropolitan area.

BACKGROUND: In the United States, breast cancer survival is worse among African-American women compared with white women. This difference in survival is likely due to several factors, including tumor biology and/or access to care. In this analysis, we evaluated the effects of sociodemographic and clinical variables on differences in breast cancer survival among African-American and white women. METHODS: The study population included 10,502 women (82% white, 18% African-American), diagnosed between 1988 and 1992 and identified through the Metropolitan Detroit Cancer Surveillance System, a member of the Surveillance, Epidemiology and End-Results (SEER) Program. Cox proportional hazards regression was used to estimate the relative risk of death comparing African-American women with white women after controlling for variables believed to influence survival. RESULTS: The mean age at diagnosis was 61 years and average length of follow-up was 34 months (range, 1-78 months). African-American women were more likely to present with regional or distant disease (45%) than were white women (37%). Although white women had better survival than African-American women during the first 4 years postdiagnosis (P < 0.0001), there were no significant differences in survival by race for women who lived longer than 4 years (P = 0.64). There was a significant interaction between age and race. The unadjusted relative risk of dying for African-American women compared with white women was 2.35 (95% confidence interval [CI], 1.88-2.93) for women younger than 50 years of age, and was 1.66 (95% CI, 1.46-1.88) for women age 50 years or older. After controlling for age, tumor size, stage, histologic grade, census-derived socioeconomic status, and residency training status, the relative risk was 1.68 (95% CI, 1.27-2.24) for women younger than 50 years of age and 1.33 (95% CI, 1.13-1.56) for women age 50 years and older. Adjustment for marital status, hospital size, and the proportion of Medicaid or Medicare discharges had no further effect on the relative risk. CONCLUSIONS: Known factors that predict survival differences between African-American and white women are more prevalent among women younger than age 50.

Aged↗
PubMed1996

Childhood cancer in the United States. A geographical analysis of cases from the Pediatric Cooperative Clinical Trials groups.

BACKGROUND: After injuries, cancer is the leading cause of death in children younger than 15 years in the United States. Despite dramatic increases in 5-year survival rates, more than 100,000 person-years of life are lost to childhood cancer each year. The exact proportion of pediatric cancer patients who receive care at centers that utilize up-to-date therapeutic protocols [such as those affiliated with the Childrens Cancer Group (CCG) or the Pediatric Oncology Group (POG)] remains unknown. The purpose of this study was to estimate the proportion and geographic distribution of childhood cancer patients in the United States who are seen at participating centers of the CCG and the POG. METHODS: Patients included 21,026 incident pediatric cancer cases diagnosed from January 1, 1989 through December 31, 1991. Observed numbers of pediatric cancer cases were compared with expected numbers of cases calculated from incidence rates obtained from the Surveillance, Epidemiology, and End Results (SEER) Program and population counts obtained from the 1990 U.S. Census Bureau. RESULTS: Approximately 94% of children younger than 15 years diagnosed with cancer are seen at an institution that is a member of either POG or CCG. Comparisons of the observed-to-expected numbers of incident cases in the age groups (birth-4 years, 5-9 years, 10-14 years, and 15-19 years) demonstrated ascertainment rates of 100, 93, 84, and 21%, respectively. In some regions within the United States the observed number of cases was significantly less than that expected number, including areas of Idaho, Oklahoma, and Virginia. In addition, there were areas in which the observed number of childhood cancer cases was substantially greater than that expected, including areas in California and Florida. CONCLUSIONS: The membership of the cooperative clinical trials groups (the POG and CCG) ascertain and provide access to state-of-the-art treatment protocols for the vast majority of pediatric cancer patients in the country. For the younger age groups, the CCG and POG may represent a mechanism of case ascertainment that approximates a population-based series for the continental United States. Those areas that have large enough discrepancies in observed-to-expected numbers may warrant further investigation.

Adolescent↗
PubMed1996

Clinical surveillance for early stage breast cancer: an analysis of claims data.

This study estimates the costs of clinical follow-up for women with early stage breast cancer and evaluates the effects of patient and provider characteristics on follow-up intensity. Claims data were cumulated from 1/1/89 through 4/30/93 for a comprehensive set of follow-up tests (office visits, radiologic, and laboratory) ordered for 222 women diagnosed at a university hospital between 1/1/89 and 12/31/91. Aggregated measures of the volume and costs of follow-up over 6 month intervals were expressed in terms of Medicare's 1993 relative value units (RVUs) and their 1993 cost equivalents. Excluding the first 6 months, women received on average, 11.7 RVUs of follow-up in the first year (equivalent to a cost of $362), and 9.5 RVUs in the second year ($297). In the first year, chest x-rays, clinical chemistry tests, automated hemograms, and bone scans, accounted for 36% of the cost of follow-up, while computerized tomographic scans and magnetic resonance imaging studies accounted for 30%. Multiple regression analysis of the first year data showed that women who received radiation and/or were followed by oncology, were more likely to receive intensive follow-up. Age, race, socioeconomic status, insurance, stage, and treatment did not impact follow-up. Costs of follow-up for breast cancer are substantial, though much lower than suggested by others. Additionally, wide variations in practice are largely unexplained by patient and/or provider characteristics. In light of recent evidence questioning the benefit of intensive surveillance, this study supports the need for an accepted set of follow-up guidelines for breast cancer.

Breast Neoplasms↗
PubMed1996

Increasing incidence of adenocarcinomas and carcinoid tumors of the small intestine in adults.

Malignant neoplasms of the small intestine are relatively rare and have received little study. We report on trends in the age-adjusted, sex-, and race-specific incidence rates of adenocarcinomas and carcinoid tumors of the small intestine in the United States from 1973 through 1991. Data were derived from the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute. There were statistically significant increases in the incidence rates of both adenocarcinomas and carcinoid tumors during the time frame of the study. Rates increased most dramatically in black males, with 2- and 4-fold increases in adenocarcinomas and carcinoid tumors, respectively. The only rates that remained relatively unchanged were those of adenocarcinoma among white females. It remains to be determined if changing environmental factors are important causes of these observed trends. If environmental factors are involved in the etiology of small intestine cancers, analytic studies conducted while the disease is increasing in incidence may provide useful insights.

Adenocarcinoma↗
PubMed1995

Incidence of cancer in children in the United States. Sex-, race-, and 1-year age-specific rates by histologic type.

BACKGROUND: Rates of cancer in children usually are presented in 5-year age groups, despite large variations of incidence within these groups. The purpose of this report is to provide histology-specific incidence rates within single-year age groups, stratified by sex and race, among children. METHODS: Data from the National Cancer Institute's SEER Program were used to calculate incidence rates among children younger than 15 years of age at diagnosis. The SEER population denominator file was modified to allow calculation of rates within single years of age. RESULTS: Large differences in rates within 5-year age groups were found for many histologic types. Retinoblastoma and Wilms' tumor, for instance, had up to eight-fold differences. Substantial differences also were observed for non-Hodgkin's lymphoma, neuroblastoma, Hodgkin's disease, acute lymphoid leukemia, acute myeloid leukemia, and osteosarcoma. In general, rates were higher among males than females, although female rates were often higher among young children. Rates of white children were generally higher than those of black children, especially during the first 5 years of life. Embryonal tumors comprised the majority of neoplasms during the first 2 years of life.

Adolescent↗
PubMed1995

Effect of age and race on the survival of men with prostate cancer in the Metropolitan Detroit tricounty area, 1973 to 1987.

OBJECTIVES: Reports have demonstrated that African Americans diagnosed with prostate cancer have a poor survival compared with whites. We examined the impact of age, race, and stage of disease on survival for men diagnosed with prostate cancer. METHODS: A retrospective analysis was made of men diagnosed with prostate cancer utilizing the Surveillance, Epidemiology, and End Results Program (SEER) database. A total of 12,907 men (9339 white, 3568 black) diagnosed from January 1, 1973 through December 31, 1987 were included in the study. For each stage of disease, survival experience was examined using Kaplan-Meier and life table methods, followed by analysis using Cox's proportional hazard model. RESULTS: African-American men have a poorer survival than whites for all stages of prostate cancer when the cancer is diagnosed at younger ages. These differences in survival were not demonstrated for men diagnosed with prostate cancer after age 70. CONCLUSIONS: Age and race should be taken into account when assessing the survival of patients with prostate cancer.

Adenocarcinoma↗
PubMed1995

Random-digit dialing for control selection in childhood cancer studies: the geographic proximity and demographics within matched sets.

The purpose of this analysis was to evaluate the degree of matching in 95 individually matched pairs from a case-control study of childhood leukemia that used random-digit dialing to select control subjects. Both geographic proximity (of each case subject to his or her matched control subject) and differences in socioeconomic status were evaluated. The median distance between matched pairs was 3.2 km. There were no significant differences in distance between matched pairs by urban/rural status and geographic location. For studies of childhood cancer drawn from pediatric referral centers, random-digit dialing appears to provide a suitable control group.

Case-Control Studies↗
PubMed1995

Prostate-specific antigen in a community screening program.

BACKGROUND: This study was designed to determine who participates in community-based prostate-specific antigen (PSA) screening programs and what serum PSA levels can be expected. METHODS: A descriptive analysis of men who participated in an annual community health screening program was used to compare men who chose PSA screening with those who did not. The relationship of demographic variables to PSA level was evaluated by multivariate regression analysis. Data were available on 5548 men, 6% of whom were black. RESULTS: The population of PSA screening participants included proportionately more middle-aged white men with higher median income, as compared with men who did not participate. Those who did not participate in the screening were more likely to be either very old or very young. PSA levels increased with age, and the percentage of men with elevated PSA levels increased with age. One tenth (9.6%) of all participants had PSAs between 4 ng/mL and 10 ng/mL, and 1.9% had levels greater than 10 ng/mL. Within 1 year of the screening, 1.7% of the screened participants had a diagnosis of prostate cancer. The mean PSA in this group was 15.9 ng/mL. CONCLUSIONS: These data confirm the need for age-specific PSA reference ranges. It is likely that the same reference range can be used for all racial ethnic populations.

Black or African American↗