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R K Ross

Publications and source records attributed to R K Ross.

At least 109 records · Page 6Linked to original sources
PubMed1994

A prospective study of pancreatic cancer in the elderly.

Risk factors for pancreatic cancer were examined in a cohort study of 13,979 residents of a retirement community. After 9 years of follow-up, 65 incident cases of pancreatic cancer were identified. An increased risk of pancreatic cancer was associated with a history of diabetes and cholecystectomy. Higher intake of vegetables, fruits, dietary beta-carotene, and vitamin C were each associated with a reduced risk of pancreatic cancer, although none of these associations was statistically significant. Risk of pancreatic cancer decreased with increasing tea consumption but was unrelated to coffee consumption. No strong or consistent association was seen between either smoking or alcohol consumption and risk of pancreatic cancer, but a consistent and significant increase in risk followed cholecystectomy.

Aged↗
PubMed1994

Acetylator phenotype, aminobiphenyl-hemoglobin adduct levels, and bladder cancer risk in white, black, and Asian men in Los Angeles, California.

BACKGROUND: There is a large body of epidemiologic and experimental data that have identified a number of arylamines as human bladder carcinogens. Metabolic activation is required to biotransform these arylamines into their carcinogenic forms, and N-hydroxylation, which is catalyzed by the hepatic cytochrome P4501A2 isoenzyme, is generally viewed as the first critical step. On the other hand, the N-acetylation reaction, catalyzed by the hepatic N-acetyltransferase enzyme, represents a detoxification pathway for such compounds. The N-acetyltransferase enzyme is coded by a single gene displaying two phenotypes, slow and rapid acetylators. In the United States, cigarette smoking is a major cause of bladder cancer in men, and carcinogenic arylamines present in cigarette smoke are believed to be responsible for inducing bladder cancer in smokers. PURPOSE: Our purpose was to test the differences in three ethnic/racial groups for the prevalence of acetylator phenotypes and to ascertain whether slow acetylators actually have higher levels of activated arylamines in comparison with rapid acetylators. METHODS: One hundred thirty-three male residents of Los Angeles County who were either white, black, or Asian (Chinese or Japanese) and over the age of 35 years were assessed for their acetylator phenotype and levels of 3- and 4-aminobiphenyl (ABP) hemoglobin adducts. Subjects were either lifetime nonsmokers (n = 72) or current cigarette smokers of varying intensity (n = 61). RESULTS: The proportion of slow acetylators was highest among whites (54%), intermediate among blacks (34%), and lowest among Asians (14%). Similarly, geometric mean levels of both 3- and 4-ABP-hemoglobin adducts were highest in whites (1.80 and 49.2 pg/g hemoglobin [Hb], respectively), intermediate in blacks (1.54 and 38.5 pg/g Hb), and lowest in Asians (0.73 and 36.0 pg/g Hb). As expected, cigarette smokers had significantly higher mean levels of both 3- and 4-ABP-hemoglobin adducts relative to nonsmokers, and the levels increased with the number of cigarettes smoked per day (P < .0005 for both adducts). Slow acetylators consistently exhibited higher mean levels of ABP-hemoglobin adducts relative to rapid acetylators, independent of race and level of smoking. CONCLUSION: The present cross-sectional survey supports acetylation phenotype as an important determinant of bladder cancer risk and a possible major factor in the varying bladder cancer risk among whites, blacks, and Asians.

Acetylation↗
PubMed1994

Relationship of serum levels of oncostatin M to AIDS-related and classic Kaposi's sarcoma.

Serum levels of circulating oncostatin-M (OM) were compared among cases of Kaposi's sarcoma associated with acquired immune deficiency syndrome (AIDS-KS) and multiple controls, including a homosexual man infected with human immunodeficiency virus type 1 (HIV-1), an HIV-1-uninfected homosexual man, and a heterosexual man; and among classic KS cases and heterosexual controls. Cases were selected from abstracts collected by a population-based cancer registry and from local AIDS clinics. Controls for the AIDS-KS cases were matched to the cases by age, sex, and race and were either friends of the cases or residents from the cases' neighborhoods; controls for the classic KS cases were similarly matched, but were obtained solely from neighborhood residents. Blood samples were obtained from participants, serum levels of OM were determined by enzyme-linked immunosorbent assay (ELISA), and CD4 cell counts were obtained by flow cytometry. Geometric mean levels of OM were compared among the risk groups adjusted for age and CD4 cell count. No differences in adjusted OM levels were found between AIDS-KS cases and HIV-1-infected homosexual controls (8.4 pg/ml vs. 10.2) or between classic KS cases and controls (13.3 pg/ml vs. 9.6); however the HIV-1-infected controls (both homosexual and heterosexual) matched to the AIDS-KS cases had higher levels than did the HIV-1-infected cases and controls. Among the HIV-1-infected groups, an inverse correlation between OM and CD4 cell count was observed and was statistically significant for the cases. Among all heterosexual controls (matched to either case group), serum OM was inversely related to age.(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired Immunodeficiency Syndrome↗
PubMed1993

The descriptive epidemiology of malignant cystosarcoma phyllodes tumors of the breast.

BACKGROUND: Malignant cystosarcoma phyllodes tumors of the breast are rare fibroepithelial tumors. The epidemiologic features of these malignancies in a defined population have not previously been described. METHODS: Incidence data were collected from 1972-1989 by the Cancer Surveillance Program, the population-based cancer registry for Los Angeles County. RESULTS: The average annual age-adjusted incidence rate of malignant cystosarcoma phyllodes is 2.1 per 1 million women. Latina whites have a higher risk of this cancer than other racial-ethnic groups. The age-incidence curve shows that risk of cystosarcoma phyllodes peaks in the 45-49-year-old age group, but the age patterns vary by race-ethnicity, with Asian and Latina patients significantly younger, on average, than non-Latina white patients. The incidence rates of malignant cystosarcoma phyllodes were substantially higher in the 1980s than in the 1970s, particularly among Latina whites and Asians. For Latina whites, birthplace is a significant predictor of risk. Women born in Mexico and Central and South America are at threefold to fourfold greater risk of malignant cystosarcoma phyllodes tumors than Latina whites born in the United States. CONCLUSIONS: The epidemiology of malignant cystosarcoma phyllodes tumors of the breast is strikingly different from that of the more common histologic types of breast cancer. The high risk in Latina immigrants may offer an important clue as to the cause of this rare tumor.

Adult↗
PubMed1993

Hormonal chemoprevention of cancer in women.

The use of oral contraceptives in the United States during the past three decades has led to a dramatic decline in the incidence of cancers of the ovary and endometrium. The magnitude of these declines was predictable both from epidemiologic data and from the biologic effects of oral contraceptives on these tissues. Although the incidence of breast cancer has not been substantially affected by current oral contraceptives, it may be possible to develop alternative forms of contraception that provide protection against all three cancers. The major goal of hormonal chemoprevention of cancer is to reduce cell proliferation in the relevant epithelial tissue. New chemopreventive agents such as tamoxifen exemplify the application of this principle.

5-alpha Reductase Inhibitors↗
PubMed1993

Endogenous hormones and breast cancer risk.

There is substantial evidence that high estrogen levels in postmenopausal women are associated with an increase in breast cancer risk, but such a relation has not yet been established in premenopausal women, despite biologic evidence that breast epithelial cell division rates are high during the luteal phase of the menstrual cycle when estradiol and progesterone levels are high. The lack of total consistency among studies that have assessed estrogen differences, whether in breast cancer patients versus controls or in subgroups of the population characterized by different risk profiles for breast cancer, is not unexpected given the extraordinarily complex methodological issues that must be addressed in these studies. There has been a clear evolution over time in the level of sophistication of these types of studies, further decreasing the likelihood of finding consistent patterns in the literature. Other hormones may play an important role in breast cancer development as well. Experimental data are particularly compelling for a role of progesterone and prolactin, but hormonal studies in women are not entirely convincing regarding the role of these two hormones, nor is the literature nearly as extensive as it is for the estrogens. Studies of various androgens are even less consistent. Moreover, such studies suffer from a lack of precise hypotheses regarding how these hormones might directly alter risk.

Breast Neoplasms↗
PubMed1993

Comparison of early and late respondents to a postal health survey questionnaire.

We mailed a health survey to the 18,408 residents of a California retirement community and compared the 11,550 respondents on a number of characteristics by time of response. Early respondents were more likely to be the "worried well," that is, healthy individuals who see their doctor regularly, receive disease detection screening, and follow healthful life-style practices. Late respondents tended to answer questions regarding their mental function and emotional status more negatively. Early and late respondents did not differ in the rates of death or hospitalization during the first 5 years of the study; nonrespondents had a higher incidence of hospitalization than respondents in year 1 and higher death rates in the first 3 years, but not thereafter.

Aged↗
PubMed1992

Prior medication use and health history as risk factors for non-Hodgkin's lymphoma: preliminary results from a case-control study in Los Angeles County.

To determine whether non-Hodgkin's lymphoma (NHL) is related to prior medication use or health history, a population-based case-control study was conducted. A total of 619 male and female residents of Los Angeles County who were diagnosed with NHL between January 1, 1979, and June 30, 1982, were compared to individually age-, race-, and sex-matched neighborhood controls with regard to history of use of 49 different medications, 47 chronic and infectious diseases or other conditions, 15 types of immunizations, and 15 specific allergic reactions. Based on preliminary analyses, long-term regular use of aspirin and other pain relievers and greater than or equal to 2 mo of treatment with penicillin and other antibiotics were associated with significantly increased risk of NHL. Other drugs associated with greater risk of NHL were use of digitalis and estrogen replacement therapy by women, use of corticosteroids, and greater than or equal to 2 mo of use of tranquilizers. NHL was strongly associated with a prior history of cancer. Cases more frequently reported histories of kidney infections and anemia than did controls; a history of eczema appeared to be protective against NHL. Women who had been immunized against polio by injectable vaccine were at significantly lower risk of NHL than women who had not received this immunization. Among men, cholera immunization and allergy to nuts and berries were significantly protective. Subjects who had received a yellow fever immunization also had lower NHL risk. Further analyses of these data will attempt to establish the relative importance of these potential risk factors and to determine whether any are markers of early symptoms of NHL.

Adult↗
PubMed1992

Urinary aflatoxin biomarkers and risk of hepatocellular carcinoma.

Aflatoxins have long been suspected to be human hepatic carcinogens but no direct study was feasible until assays to measure individual aflatoxin exposure became available. We have used assays for urinary aflatoxin B1, its metabolites AFP1 and AFM1, and DNA-adducts (AFB1-N7-Gua) to assess the relation between aflatoxin exposure and liver cancer, as part of an ongoing prospective study of 18,244 middle-aged men in Shanghai, People's Republic of China. After 35,299 person-years of follow-up, 22 cases of liver cancer had been identified. For each case, 5 or 10 controls were randomly selected from cohort members without liver cancer on the date the disorder was diagnosed in the case and matched to within 1 year for age, within 1 month for sample collection, and for neighbourhood of residence. Subjects with liver cancer were more likely than were controls to have detectable concentrations of any of the aflatoxin metabolites (relative risk 2.4, 95% confidence interval 1.0-5.9). The highest relative risk was for aflatoxin P1 (6.2, 1.8-21.5). In an analysis adjusting for the effects of hepatitis B surface antigen seropositivity, level of education, cigarette smoking, and alcohol consumption, the relative risk for the presence of aflatoxin metabolites was 3.8 (1.2-12.2). There was a strong interaction between serological markers of chronic hepatitis B infection and aflatoxin exposure in liver-cancer risk. Reduction of aflatoxin exposure may be a useful intermediate goal in prevention of liver cancer, since the benefits of wide-scale hepatitis B vaccination will not be apparent for many years.

Aflatoxins↗
PubMed1992

5-alpha-reductase activity and risk of prostate cancer among Japanese and US white and black males.

The incidence of prostate cancer varies widely between countries and ethnic groups. Black-Americans have the highest incidence rates world wide, whereas native Japanese have among the lowest. The reasons for this risk differential are unknown, although we have previously shown that higher circulating testosterone concentrations in young adult black men compared with young adult white men may explain the underlying differences in subsequent prostate cancer incidence between these two populations. We have now compared serum testosterone concentrations in young adult Japanese men with those of young adult whites and blacks, but found no significant differences. However, these white and black men had significantly higher values of 3 alpha, 17 beta androstanediol glucuronide (31% and 25% higher, respectively) and androsterone glucuronide (50% and 41% higher, respectively) than Japanese subjects. These two androgens are indices of 5 alpha-reductase activity. Our results raise the possibility that reduced 5 alpha-reductase activity has a role in producing the low prostate cancer incidence rates among Japanese. This finding may have important implications for prostate cancer prevention.

Adult↗
PubMed1992

Prospects for the primary prevention of breast cancer.

In this paper, the rationale, stage of development, and known or potential adverse effects of three potential strategies for the prevention of breast cancer are reviewed. Two methods--the use of tamoxifen in postmenopausal women and the use of luteinizing hormone (LH)-releasing hormone agonists in premenopausal women--involve hormonal manipulation. In the premenopausal period, the goal is to reduce the number of ovulatory menstrual cycles a woman experiences in order to reduce her exposure to estrogen and progesterone. Physical activity during adolescence is proposed as a nonhormonal method of accomplishing this. The use of LH-releasing hormone agonists to produce a reversible menopause can also reduce a woman's cumulative exposure to ovarian steroid hormones. Tamoxifen, which is effective in breast cancer therapy, provides endocrine control of estrogen-regulated breast tumor growth. Breast cancer chemoprevention trials using tamoxifen among postmenopausal women have been proposed, and pilot studies are under way.

Adolescent↗