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Biomedical subjects

R K Ross

Publications and source records attributed to R K Ross.

At least 19 recordsLinked to original sources
PubMed1995

A cohort study of serum testosterone and hepatocellular carcinoma in Shanghai, China.

A nested case-control study of HCC based on a cohort of 18,244 middle-aged men in Shanghai, China, who had been followed for an average of 5.3 years, was conducted. Our hypothesis dealt with the possible role of testosterone in the etiology of HCC, which shows a minimum of a 2- to 3-fold male excess in all populations world-wide. Seventy-six incident cases of HCC and 410 control subjects drawn from the cohort and individually matched to the cases by age (within 1 year), time of blood sample collection (within 1 month) and neighborhood of residence were assessed for serum HBsAg, anti-HBc, anti-HBs, anti-HCV and testosterone. Among controls, serum testosterone levels were similar between those who had no markers of HBV infection, those who were positive for anti-HBs only and those who were positive for anti-HBc but negative for HBsAg. However, the geometric mean level of testosterone in HBsAg-positive controls was 21% higher relative to HBsAg-negative controls and the difference was statistically significant (2-sided p = 0.0006). Relative to controls, HCC cases had a significantly higher mean level of testosterone at the time of recruitment (570 vs. 485 ng/dl, 2-sided p = 0.0005), but the difference was explicable on the basis of a higher proportion of HBsAg-positive individuals among cases than controls (p = 0.42 after adjustment for HBsAg status).

Age Factors↗
PubMed1995

Cancer incidence among Filipinos in Los Angeles County, 1972-1991.

Although Filipinos are the second largest Asian subgroup in the United States, little is known about their patterns of cancer incidence. We have examined cancer incidence rates among Filipinos living in Los Angeles County from 1972 through 1991 and evaluated their risk of non-localized cancer relative to non-Hispanic whites. Although Filipinos have substantially lower cancer rates than non-Hispanic whites in Los Angeles County, their incidence rates of liver cancer, cancer of the nasopharynx and thyroid cancer are higher. Filipino men and women had somewhat more advanced cancer at diagnosis, on average, than non-Hispanic whites, though no statistically significant differences were observed for sites where early detection methods exist. Our data suggest that Filipino-Americans would benefit from increased screening for cervical and breast cancer as well as efforts to interrupt transmission of hepatitis B virus to reduce liver cancer incidence.

Aged↗
PubMed1995

Correlation of estrogen levels between successive pregnancies.

To date, no study has attempted to correlate hormone levels between successive pregnancies in the same woman. Serum levels of total estradiol and total free estradiol have been measured between the eighth and the 17th weeks in the first and second full-term pregnancies of 34 white women participating in the Collaborative Perinatal Study, 1959-1965. Intraindividual interpregnancy Pearson's product moment correlations were calculated. Partial correlation coefficients (adjusted for gestational age) for log pregnancy total estradiol and total free estradiol were 0.78 and 0.73, respectively (p < 0.001). These findings provide evidence that levels of pregnancy estradiol are significantly and strongly correlated in successive pregnancies of the same woman. This phenomenon can provide an explanation for the higher concordance of breast cancer incidence between two sisters than between a mother and daughter in the familial pattern of breast cancer.

Breast Neoplasms↗
PubMed1995

Genetic variability of the human SRD5A2 gene: implications for prostate cancer risk.

Elevated dihydrotestosterone levels have been suggested to increase the risk of prostate cancer. The human SRD5A2 gene encodes the type II steroid 5 alpha-reductase, which converts testosterone to the more bioactive compound dihydrotestosterone. We have determined the distribution of a dinucleotide repeat in low-risk Asian-Americans, high-risk African-Americans, and intermediate-risk non-Hispanic Whites. We found this marker to be more polymorphic than previously reported, with some alleles being specific to African-Americans. Genetic variants of the SRD5A2 gene may play a role in predisposition to prostate cancer and in explaining the substantial racial/ethnic variability in risk.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1995

The CAG and GGC microsatellites of the androgen receptor gene are in linkage disequilibrium in men with prostate cancer.

The androgen receptor genotype was determined in the white blood cell DNA of 45 African-American, 39 non-Hispanic white, and 39 Asian (Chinese, Japanese) normal subjects and 68 patients with prostate cancer (57 whites), all of whom were residents of Los Angeles County. For each subject, we measured the number of repeats in the polymorphic CAG and GGC microsatellites of exon 1 of the androgen receptor gene. In normal subjects, the distributions of CAG and GGC microsatellites differed significantly among the races (two-sided P = 0.046 and < 0.0005, respectively). The prevalence of short CAG alleles (< 22 repeats) was highest (75%) in African-American males with the highest risk for prostate cancer, intermediate (62%) in intermediate-risk non-Hispanic whites, and lowest (49%) in Asians at very low risk for prostate cancer. High-risk African-Americans also had the lowest frequency (20%) of the GGC allele with 16 repeats; the comparable values for intermediate-risk whites and low-risk Asians were 57% and 70%, respectively. Consistent with the interracial variation in CAG and GGC distributions, there was an excess of white patients with < 22 CAG and not-16 GGC repeats relative to white controls (relative risk, 2.1; one-sided P = 0.08). We observed no association (linkage) between the two microsatellites among normal subjects. On the other hand, there was a statistically significant negative association between the numbers of CAG and GGC repeats among the prostate cancer patients studied (two-sided P = 0.008). Among the 47 subjects with short CAG alleles (< 22 repeats), 43% had long GGC alleles (> 16 repeats) whereas only 15% of the 20 subjects with long CAG alleles (> or = 22 repeats) had long GGC alleles. Overall, our data suggest a possible association between CAG and GGC microsatellites of the androgen receptor gene and prostate cancer development.

Adult↗
PubMed1995

Diet and breast cancer in Shanghai and Tianjin, China.

Various aspects of adult diet have been linked to breast cancer development. These include intake of fat (risk factor), and intake of fibre, soy protein and vitamins A, C and E (protective factors). Results of previous studies have been inconsistent. We examined the possible associations between breast cancer and various indices of nutrient and food intake in two Chinese populations who are at relatively low risk for breast cancer (one-fifth the rate in US white women). Two case-control studies of breast cancer were conducted in the cities of Shanghai and Tianjin, China. In Shanghai, 534 women aged 20-69 years with histologically confirmed breast cancer were recruited, whereas in Tianjin 300 women aged 20-55 years with histologically confirmed breast cancer were interviewed. All controls were community controls who were individually matched to the cases by sex and age (case-control ratio = 1:1). All interviews were conducted in person. Findings from the two studies were similar, although the diets in Shanghai and Tianjin were different in many respects. Cases and controls were similar in their consumption of soy protein, measured either in absolute levels or as percentages of total protein. Overall, all components of dietary fat (saturated fat, monounsaturated fat, polyunsaturated fat) showed a modest, non-significant association with breast cancer after adjustment for energy intake and other non-dietary risk factors for breast cancer. Intake of crude fibre, carotene and vitamin C, on the other hand, exhibited strong, statistically significant inverse associations with breast cancer risk. The last three indices were highly correlated, rendering it impossible to disentangle their individual effects; they were closely associated with intake of green vegetables in the two study populations. Vitamin E intake was unrelated to breast cancer risk in Shanghai and Tianjin. In the multivariate logistic regression model which included all non-dietary risk factors for breast cancer and energy intake, Shanghai women in the lowest tertile of crude fibre intake and highest tertile of fat intake had a 2.9-fold increased risk for breast cancer relative to those in the highest tertile of crude fibre intake and lowest tertile of fat intake. The comparable relative risk in Tianjin women was 2.4. Our data indicate a strong protective effect against breast cancer development with intake of foods rich in fibre, vitamin C and carotene. Our results are also compatible with dietary fat having a modest, positive effect on breast cancer risk within the range of exposure experienced by women in China.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Evidence of an X-linked or recessive genetic component to prostate cancer risk.

We used data from a population-based cohort study of blacks, Hispanics, Japanese and whites to examine the frequency of prevalent prostate and breast cancer by family history status of first-degree relatives (parents and siblings). Independent of race, the age-adjusted relative risk for prevalent prostate cancer in subjects with affected brothers was approximately two times that in subjects with affected fathers (P < 0.00005). No such excess risk for breast cancer was observed among subjects with affected sisters compared to those with affected mothers (age- and race-adjusted relative risk = 1.10, P = 0.34). The magnitude of the relative risk for prostate cancer in sibling- versus parent-affected groups was significantly different from that of the comparable relative risk for breast cancer (P < 0.00005). An excess risk of prostate cancer in men with affected brothers compared to those with affected fathers is consistent with the hypothesis of an X-linked, or recessive, model of inheritance.

Breast Neoplasms↗
PubMed1994

Physical exercise and reduced risk of breast cancer in young women.

BACKGROUND: Epidemiologic evidence strongly suggests that cumulative exposure to ovarian hormones is a determinant of breast cancer risk. Because physical activity can modify menstrual cycle patterns and alter the production of ovarian hormones, it may reduce breast cancer risk; yet few epidemiologic studies have assessed this relationship. PURPOSE: The major objective of this study was to determine whether young women (aged 40 and younger) who regularly participated in physical exercise activities during their reproductive years had a reduced risk of breast cancer. METHODS: Using a case-control design, we conducted personal interviews of a total of 545 women (aged 40 and younger at diagnosis) who had been newly diagnosed with in situ or invasive breast cancer between July 1, 1983, and January 1, 1989, and a total of 545 control subjects. Case patients and control subjects were individually matched on date of birth (within 36 months), race (white), parity (nulliparous versus parous), and neighborhood of residence. Lifetime histories of participation in physical exercise activities on a regular basis were obtained during the personal interview. RESULTS: After adjustment for potential confounding factors, we found that the average number of hours spent in physical exercise activities per week from menarche to 1 year prior to the case patient's diagnosis was a significant predictor of reduced breast cancer risk (two-sided P for trend < .0001). The odds ratio (OR) of breast cancer among women who, on average, spent 3.8 or more hours per week participating in physical exercise activities was 0.42 (95% confidence limits [CLs] = 0.27, 0.64) relative to inactive women. The effect was stronger among women who had had a full-term pregnancy. Comparing most active (> or = 3.8 hours/wk of exercise) women to inactive women, the ORs were 0.28 (95% CL = 0.16, 0.50) for parous and 0.73 (95% CL = 0.38, 1.41) for nulliparous women. CONCLUSIONS: Most previously identified risk factors for breast cancer are reproductive and menstrual events that cannot be readily altered. The protective effect of exercise on breast cancer risk in the women whom we studied suggests that physical activity offers one modifiable lifestyle characteristic that may substantially reduce a woman's lifetime risk of breast cancer. IMPLICATIONS: Whether the protective effects of exercise on breast cancer risk are due to alterations in ovarian function and whether they extend into women's menopausal years need to be established. Our results suggest that implementation of regular physical exercise programs as a critical component of a healthy lifestyle should be a high priority for adolescent and adult women.

Adolescent↗
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↗