Do stretch-induced changes in intracellular calcium modify the electrical activity of cardiac muscle?

Stretch of the myocardium influences the shape and amplitude of the intracellular Ca(2+)([Ca(2+)](i)) transient. Under isometric conditions stretch immediately increases myofilament Ca(2+) sensitivity, increasing force production and abbreviating the time course of the [Ca(2+)](i) transient (the rapid response). Conversely, muscle shortening can prolong the Ca(2+) transient by decreasing myofilament Ca(2+) sensitivity. During the cardiac cycle, increased ventricular dilation may increase myofilament Ca(2+) sensitivity during diastolic filling and the isovolumic phase of systole, but enhance the decrease in myofilament Ca(2+) sensitivity during the systolic shortening of the ejection phase. If stretch is maintained there is a gradual increase in the amplitude of the Ca(2+) transient and force production, which takes several minutes to develop fully (the slow response). The rapid and slow responses have been reported in whole hearts and single myocytes. Here we review stretch-induced changes in [Ca(2+)](i) and the underlying mechanisms. Myocardial stretch also modifies electrical activity and the opening of stretch-activated channels (SACs) is often used to explain this effect. However, the myocardium has many ionic currents that are regulated by [Ca(2+)](i) and in this review we discuss how stretch-induced changes in [Ca(2+)](i) can influence electrical activity via the modulation of these Ca(2+)-dependent currents. Our recent work in single ventricular myocytes has shown that axial stretch prolongs the action potential. This effect is sensitive to either SAC blockade by streptomycin or the buffering of [Ca(2+)](i) with BAPTA, suggesting that both SACs and [Ca(2+)](i) are important for the full effects of axial stretch on electrical activity to develop.

Rapid microsatellite analysis using discontinuous polyacrylamide gel electrophoresis

A method for screening large numbers of samples for microsatellites using discontinuous, non-denaturing polyacrylamide gels and rapid fluorescent gel staining is described. Disc electrophoresis on slab gels provides high-resolution of PCR products. It is useful for collecting population data once microsatellite loci have been characterized.

Alcohol, tobacco and breast cancer--collaborative reanalysis of individual data from 53 epidemiological studies, including 58,515 women with breast cancer and 95,067 women without the disease

Alcohol and tobacco consumption are closely correlated and published results on their association with breast cancer have not always allowed adequately for confounding between these exposures. Over 80% of the relevant information worldwide on alcohol and tobacco consumption and breast cancer were collated, checked and analysed centrally. Analyses included 58,515 women with invasive breast cancer and 95,067 controls from 53 studies. Relative risks of breast cancer were estimated, after stratifying by study, age, parity and, where appropriate, women's age when their first child was born and consumption of alcohol and tobacco. The average consumption of alcohol reported by controls from developed countries was 6.0 g per day, i.e. about half a unit/drink of alcohol per day, and was greater in ever-smokers than never-smokers, (8.4 g per day and 5.0 g per day, respectively). Compared with women who reported drinking no alcohol, the relative risk of breast cancer was 1.32 (1.19-1.45, P<0.00001) for an intake of 35-44 g per day alcohol, and 1.46 (1.33-1.61, P<0.00001) for >/=45 g per day alcohol. The relative risk of breast cancer increased by 7.1% (95% CI 5.5-8.7%; P<0.00001) for each additional 10 g per day intake of alcohol, i.e. for each extra unit or drink of alcohol consumed on a daily basis. This increase was the same in ever-smokers and never-smokers (7.1% per 10 g per day, P<0.00001, in each group). By contrast, the relationship between smoking and breast cancer was substantially confounded by the effect of alcohol. When analyses were restricted to 22 255 women with breast cancer and 40 832 controls who reported drinking no alcohol, smoking was not associated with breast cancer (compared to never-smokers, relative risk for ever-smokers=1.03, 95% CI 0.98-1.07, and for current smokers=0.99, 0.92-1.05). The results for alcohol and for tobacco did not vary substantially across studies, study designs, or according to 15 personal characteristics of the women; nor were the findings materially confounded by any of these factors. If the observed relationship for alcohol is causal, these results suggest that about 4% of the breast cancers in developed countries are attributable to alcohol. In developing countries, where alcohol consumption among controls averaged only 0.4 g per day, alcohol would have a negligible effect on the incidence of breast cancer. In conclusion, smoking has little or no independent effect on the risk of developing breast cancer; the effect of alcohol on breast cancer needs to be interpreted in the context of its beneficial effects, in moderation, on cardiovascular disease and its harmful effects on cirrhosis and cancers of the mouth, larynx, oesophagus and liver.

Different regional effects of voluntary exercise on the mechanical and electrical properties of rat ventricular myocytes

Short-term (6 weeks) voluntary wheel running exercise in young female rats that were in an active growth phase resulted in whole-heart hypertrophy and myocyte concentric hypertrophy, when compared to sedentary controls. The cross-sectional area of ventricular myocytes from trained rats was significantly greater than for those isolated from sedentary rats, with the greatest change in morphology seen in sub-endocardial cells. There was no statistically significant effect of training on cell shortening in the absence of external mechanical loading, in [Ca2+](i) transients, or in myofilament Ca2+ sensitivity (assessed during re-lengthening following tetanic stimulation). Under the external mechanical load of carbon fibres, absolute force developed in myocytes from trained rats was significantly greater than in those from sedentary rats. This suggests that increased myocyte cross-sectional area is a major contractile adaptation to exercise in this model. Training did not alter the passive mechanical properties of myocytes or the relative distribution of titin isomers, which was exclusively of the short, N2B form. However, training did increase the steepness of the active tension-sarcomere length relationship, suggesting an exercise-induced modulation of the Frank-Starling mechanism. This effect would be expected to enhance cardiac contractility. Training lengthened the action potential duration of sub-epicardial myocytes, reducing the transmural gradient in action potential duration. This observation may be important in understanding the cellular causes of T-wave abnormalities found in the electrocardiograms of some athletes. Our study shows that voluntary exercise modulates the morphological, mechanical and electrical properties of cardiac myocytes, and that this modulation is dependent upon the regional origin of the myocytes.

Cardiac microtubules are more resistant to chemical depolymerisation in streptozotocin-induced diabetes in the rat

Evidence exists for a specific diabetic cardiomyopathy independent of concurrent vascular disease. Our aim was to test the hypothesis that a change in the microtubular cytoskeleton may contribute to cardiac dysfunction in type-1 diabetes. Resting sarcomere length and characteristics of unloaded shortening were measured in ventricular myocytes from rats 2 months after injection of streptozotocin (STZ). Microtubular density and organisation were assessed using immunofluorescence confocal microscopy and the effects of microtubule disruption by colchicine on shortening and microtubules were examined. Diabetic myocytes showed a significant reduction in resting sarcomere length and a 30% increase in time to peak shortening. The microtubule disruptor colchicine (10 micromol/l) had no effect on the amplitude or kinetics of shortening in myocytes from control or diabetic rats. Cardiac microtubular density and organisation were similar in control and diabetic animals, yet although colchicine significantly reduced microtubule density in control myocytes, microtubules in diabetic myocytes were resistant to its effects. These observations of an increase in microtubular stability in STZ-diabetes of 2 months duration imply a disruption to the normal balance between populations of dynamic and drug-stable microtubules. Such disruption has been observed in other pathological conditions and may contribute to diabetic cardiomyopathy.

Effects of hyperosmotic shrinking on ventricular myocyte shortening and intracellular Ca(2+) in streptozotocin-induced diabetic rats

Evidence exists for a specific diabetic cardiomyopathy independent of concurrent vascular disease. We tested the hypothesis that chronic hyperglycaemia found in streptozotocin- (STZ) induced diabetic rats leads to an altered response to and contractile effects of hyperosmotic shrinkage in ventricular myocytes. Analysis confirmed significant hyperglycaemia and revealed significant blood hyperosmolarity in STZ-treated rats. Myocyte volume changes, shortening and intracellular Ca(2+) ([Ca(2+)](i)) transients were measured in cells superfused with normal Tyrode (NT, 300 mmol/kg) and then hyperosmotic Tyrode (HT, 440 mmol/kg) at 35-36 degrees C. Shrinking significantly reduced the amplitude of shortening, whilst the [Ca(2+)](i) transient was significantly increased. The time course of both shortening and the [Ca(2+)](i) transient were prolonged in myocytes from STZ-treated compared to control rats. Time to peak shortening was 130.3 ms in STZ compared to 100.2 ms in control myocytes. Time to peak [Ca(2+)](i) transient was 70.8 ms in STZ compared to 44.6 ms in control myocytes and the time from peak to half recovery was 191.0 ms in STZ compared to 169.1 ms in control myocytes. Fractional SR Ca(2+) release, assessed by the application of caffeine, was increased by shrinking. However, the effects of raised extracellular osmolarity on volume changes, contractility and [Ca(2+)](i) were not altered by the chronic hyperglycaemia found in STZ-treated rats.

The association of dietary fat and plant foods with endometrial cancer (United States)

OBJECTIVES

To examine the associations of dietary fat and selected plant foods with endometrial cancer in a population-based case-control study.

METHODS

Six hundred and seventy-nine incident cases of endometrial cancer diagnosed between 1985 and 1991, and 944 population-based controls completed a 98-item semi-quantitative food-frequency questionnaire and a detailed in-person interview which collected information on endometrial cancer risk factors. Logistic regression was used to estimate odds ratios (OR) and their 95% confidence intervals (CI) of endometrial cancer, adjusted for age, county, energy intake, hormone use, smoking and, in separate models, for body mass index (BMI: kg/m2).

RESULTS

Percent energy from fat was associated with an increased risk of endometrial cancer (highest quintile cf. lowest: OR = 1.8, 95% CI 1.3-2.6), with saturated and monounsaturated fats being the main contributors of risk. There was a stronger association between dietary fat and endometrial cancer among groups with higher circulating estrogen levels (i.e. women with higher BMI, users of unopposed estrogens, non-smokers, and younger age at menarche). Consumption of fruits or vegetables was inversely associated with endometrial cancer risk (highest quintile cf. lowest: OR = 0.65, 95% CI 0.46-0.93 and OR = 0.61, 95% CI 0.43-0.88, respectively). Further adjustment for BMI resulted in little or no attenuation of the ORs and associated CIs.

CONCLUSIONS

These results provide support for the theory that a low-fat, high-fruit and high-vegetable diet may reduce the risk of endometrial cancer, and that these dietary factors may act independently of the effect of BMI.

p53-dependent apoptosis pathways

The p53 tumor suppressor limits cellular proliferation by inducing cell cycle arrest and apoptosis in response to cellular stresses such as DNA damage, hypoxia, and oncogene activation. Many apoptosis-related genes that are transcriptionally regulated by p53 have been identified. These are candidates for implementing p53 effector functions. In response to oncogene activation, p53 mediates apoptosis through a linear pathway involving bax transactivation, Bax translocation from the cytosol to membranes, cytochrome c release from mitochondria, and caspase-9 activation, followed by the activation of caspase-3, -6, and -7. p53-mediated apoptosis can be blocked at multiple death checkpoints, by inhibiting p53 activity directly, by Bcl-2 family members regulating mitochondrial function, by E1B 19K blocking caspase-9 activation, and by caspase inhibitors. Understanding the mechanisms by which p53 induces apoptosis, and the reasons why cell death is bypassed in transformed cells, is of fundamental importance in cancer research, and has great implications in the design of anticancer therapeutics.

Adenovirus infection of primary malignant lymphoid cells

Adenovirus infection represents a cellular stress that induces host cell pro-apoptotic responses. To overcome this barrier to productive infection, viral polypeptides modulate a variety of host cell pathways. The interface of these early viral gene products with key cellular regulatory proteins has provided considerable information concerning basic cellular mechanisms operative in cell cycle regulation, transcriptional control and apoptosis. The overlap of these mechanisms with those impacted during oncogenesis provides the opportunity to use adenoviruses and adenovirus mutants to characterize the state of key regulatory pathways in specific malignant cells. For example, adenoviruses mediate cytotoxicity after infection of chronic lymphocytic leukemia (CLL) cells, mantle cell lymphoma (MCL) cells and multiple myeloma cell lines. Specific adenovirus mutants demonstrate enhanced cytotoxicity and, in many cases, apoptosis is not the primary mechanism of cell death. Analysis of these infections with respect to both the features of the primary malignant cell and the mechanisms of adenovirus-mediated cytotoxicity holds the prospect of providing novel insights into the status of key regulatory pathways in individual patient malignant cells. These studies also hold the prospect of supporting the development of specific attenuated adenoviruses as therapeutic agents with selective cytotoxicity for specific primary lymphoid malignancies.

A study of some characteristics of individual clones of Schistosoma mansoni with emphasis on the biological and metabolic activities

The variability within schistosome populations was explored using mixed populations of cercariae from multimiracidial snail infections and individual clones of Schistosoma mansoni cercariae obtained from monomiracidial snail infections. We investigated the heterogeneity between different clones of S. mansoni with respect to infectivity and metabolism. One difference between clones of cercariae was found in the recovery of adult worms from Balb/C mice. Recovery of adult worms was greater after infections with a mixed population than with a clonal population. To investigate some biochemical features of individuals in clones or mixed populations, the uptake of [35S]methionine into individual parasites and their membrane proteins was measured. Isoelectric focusing of a soluble membrane fraction: the frozen-thawed supernatant extracted from individual clones, showed the presence of proteins of isoelectric point between 7.2 and 8.2 in all clones. These proteins were less labelled with [35S]methionine in the clones than in the mixed population. It was concluded that basic proteins are synthesized by all clones and in the mixed population but at different rates. Differences in the rate of incorporation of [35S]methionine into the surface membranes of schistosomula and adult worms derived from individual clones are reported. In addition, a direct correlation between the percentage of recovery of adult worms from mice infected with individual clones of S. mansoni and the rate of incorporation of [35S]methionine into schistosomula of these particular clones was observed. It is suggested that the high rate of metabolism shown by an individual clone may account for the enhanced survival of the cercariae derived from that clone during penetration of the skin and migration through the vertebrate host. In order to examine individuals in a population of schistosomula, from a clone or mixed population, the lysosome-specific fluorescent probe LysoTracker DND-99 was used to label the parasites and quantitative fluorescent measurements were made on individual parasites. There were significant differences between clones and a mixed population. Furthermore, the variation between individuals from a mixed population was greater than from that in any clone, just as was found in the infectivity studies. Freshly transformed schistosomula of individual clones labelled with the LysoTracker DND-99 showed less variations in the quantitative uptake of the dye within a single clone when compared to the mixed population. We conclude that for any biochemical and biological parameter, a population of cercariae consists of individuals showing a wide range of values, with a much greater range in a mixed population. This variability is likely to have great relevance for infectivity of the final host and the efficacy of drugs and the immune system.

Tumor necrosis factor-alpha induces Bax-Bak interaction and apoptosis, which is inhibited by adenovirus E1B 19K

Tumor necrosis factor (TNF)-alpha-mediated death signaling induces oligomerization of proapoptotic Bcl-2 family member Bax into a high molecular mass protein complex in mitochondrial membranes. Bax complex formation is associated with the release of cytochrome c, which propagates death signaling by acting as a cofactor for caspase-9 activation. The adenovirus Bcl-2 homologue E1B 19K blocks TNF-alpha-mediated apoptosis by preventing cytochrome c release, caspase-9 activation, and apoptosis of virus-infected cells. TNF-alpha induces E1B 19K-Bax interaction and inhibits Bax oligomerization. Oligomerized Bax may form a pore to release mitochondrial proteins, analogous to the homologous pore-forming domains of bacterial toxins. E1B 19K can also bind to proapoptotic Bak, but the functional significance is not known. TNF-alpha signaling induced Bak-Bax interaction and both Bak and Bax oligomerization. E1B 19K was constitutively in a complex with Bak, and blocked the Bak-Bax interaction and oligomerization of both. The TNF-alpha-mediated cytochrome c and Smac/DIABLO release from mitochondria was inhibited by E1B 19K expression in adenovirus-infected cells. Since either Bax or Bak is essential for death signaling by TNF-alpha, the interaction between E1B 19K and both Bak and Bax may be required to inhibit their cooperative or independent oligomerization to release proteins from mitochondria which promote caspase activation and cell death.

The scientific study of unusual rapid wound healing: a case report

This paper examines in a Western medical setting the claim made by a Middle Eastern school of Sufism that its members can attain unusually rapid wound healing from deliberately caused bodily damage. The demonstration involved a Sufi practitioner inserting an unsterilized metal skewer through one side of the cheek area of the face (lateral buccal) and out through the other side. The insertion was observed by Western scientists. The left facial puncture healed within 2 minutes; the right facial puncture was three-quarters healed after 8 hours. According to the practitioner, the piercing was not associated with subjective pain. Radiological, immunological, and electroencephalograph (EEG) recordings were taken before and after the insertion. A random event generator (REG) was also run during the demonstration. Radiological and axial CT images documented the presence of the metal skewer through the cheeks. EEG findings were inconclusive. Immunological recordings showed no alterations. There was a trend toward REG non-randomness and, therefore, negentropy or increased complexity and order, which may be associated with the re-establishment of tissue integrity. Such rapid wound healing has therapeutic implications for new treatments of serious medical and pain-related problems as well as implications for the study of "paranormal" healing phenomena.

The association of dietary fat and plant foods with endometrial cancer (United States)

OBJECTIVES

To examine the associations of dietary fat and selected plant foods with endometrial cancer in a population-based case-control study.

METHODS

Six hundred and seventy-nine incident cases of endometrial cancer diagnosed between 1985 and 1991, and 944 population-based controls completed a 98-item semi-quantitative food-frequency questionnaire and a detailed in-person interview which collected information on endometrial cancer risk factors. Logistic regression was used to estimate odds ratios (OR) and their 95% confidence intervals (CI) of endometrial cancer, adjusted for age, county, energy intake, hormone use, smoking and, in separate models, for body mass index (BMI: kg/m2).

RESULTS

Percent energy from fat was associated with an increased risk of endometrial cancer (highest quintile cf. lowest: OR = 1.8, 95% CI 1.3-2.6), with saturated and monounsaturated fats being the main contributors of risk. There was a stronger association between dietary fat and endometrial cancer among groups with higher circulating estrogen levels (i.e. women with higher BMI, users of unopposed estrogens, non-smokers, and younger age at menarche). Consumption of fruits or vegetables was inversely associated with endometrial cancer risk (highest quintile cf. lowest: OR = 0.65, 95% CI 0.46-0.93 and OR = 0.61, 95% CI 0.43-0.88, respectively). Further adjustment for BMI resulted in little or no attenuation of the ORs and associated CIs.

CONCLUSIONS

These results provide support for the theory that a low-fat, high-fruit and high-vegetable diet may reduce the risk of endometrial cancer, and that these dietary factors may act independently of the effect of BMI.

Asian breast cancer survival in the US: a comparison between Asian immigrants, US-born Asian Americans and Caucasians

BACKGROUND

This study examines whether acculturation of Asian American women, assessed by place of birth, is associated with survival after diagnosis of breast cancer. We hypothesized that environmental factors associated with acculturation, such as a high-fat diet, would result in a pattern of better survival for first-generation Asians compared with subsequent-generation Asian Americans.

METHODS

Analyses compare survival among women of four ethnic groups (Chinese [n = 1842], Japanese [n = 3319], Filipino [n = 1598] and a random sample of Caucasians [n = 10,000]) who were diagnosed with primary invasive breast carcinoma in three Surveillance, Epidemiology, and End Results Program (SEER) regions (San Francisco/Oakland, Hawaii, Seattle/Puget Sound) between 1973 and 1994. Analyses by birthplace compare first-generation Asian immigrants with subsequent-generation Asian Americans of the same ethnicity. Analyses were based on the Cox proportional hazards model and adjusted for age at diagnosis, stage of disease, year of diagnosis, type of treatment, marital status, and SEER region.

RESULTS

Japanese women had significantly better survival than all other races, but there were no significant differences in survival between Chinese, Filipino, and Caucasian women. There were no significant differences in survival by place of birth within each Asian ethnic group, after adjustment for demographic characteristics, stage of disease, and treatment.

CONCLUSION

The findings do not support the hypothesis that acculturation of Asian American women is associated with decreased breast cancer survival.

Corticosteroids in idiopathic pulmonary fibrosis

Corticosteroids were the mainstay of therapy for idiopathic pulmonary fibrosis (IPF) for more than four decades, but their efficacy is unproven and toxicities are substantial. The course of IPF is characterized by progressive respiratory insufficiency, leading to death within 3 to 8 years from the onset of symptoms. Although a subset (10-20%) of patients survives more than 10 years, there is no evidence that any form of therapy alters the natural history of the disease. Nonetheless, given the poor prognosis, a trial of corticosteroids is often given. Because of the rarity of IPF, randomized, placebo-controlled therapeutic trials have not been done. Further, no studies have compared differing dosages or duration of corticosteroid in matched patients. Interpretation of therapy efficacy is obscured by several factors including heterogeneous patient populations, inclusion of patients with histologic entities other than usual interstitial pneumonia, lack of objective, validated endpoints, different criteria for "response." We review published data regarding corticosteroid therapy for IPF and present a rationale for stratifying therapy based on host, demographic, and clinical factors that influence prognosis as well as risk for corticosteroid complications.

Melanoma risk in relation to height, weight, and exercise (United States)

Height and weight and derivations thereof are positively associated with a number of cancers. While several authors have reported an increased risk of melanoma among people at the higher extremes of these measures, the association has not been fully explored. New cases of primary cutaneous melanoma in 1997 in western Washington State (n = 386) were compared to controls selected by random-digit dialing (n = 727). Each study participant completed a telephone survey, and data were collected on height, weight, sun-related melanoma risk factors, demographic characteristics, as well as habits such as diet and exercise. Risk of melanoma was analyzed by logistic regression with adjustment for age, hair color, lifetime sun exposure, and fruit and vegetable intake. An excess risk of melanoma was identified in men in the upper quartiles of height (OR = 2.4, 95% confidence interval (CI) = 1.3-4.5), weight (OR = 2.8, CI = 1.5-5.2), and body surface area (OR = 2.8, CI = 1.5-5.1) vs. the lowest quartiles. In women, no association was present for any anthropometric measure. In addition, we found that men and women exercising five to seven days per week were at a decreased risk of melanoma (OR = 0.7, CI = 0.5-1.0). The anthropometric findings are largely consistent with previous studies, while this is the first report of an association of exercise with melanoma risk. The mechanisms for the effect of exercise and for the difference between men and women in the effect of anthropometric factors are unknown. Future research in basic and epidemiologic science should focus on biochemical or behavioral explanations for these observations.

E1B 19K blocks Bax oligomerization and tumor necrosis factor alpha-mediated apoptosis

Tumor necrosis factor alpha (TNF-alpha)-mediated death signaling causes the recruitment of monomeric pro- apoptotic Bax into a 500-kDa protein complex. The adenovirus Bcl-2 homologue, E1B 19K, inhibits TNF-alpha-mediated apoptosis, interacts with Bax, and blocked the formation of the 500-kDa Bax complex. TNF-alpha and truncated Bid induced Bax-Bax cross-linking, indicative of oligomerization, and E1B 19K expression during infection inhibited this TNF-alpha-mediated Bax oligomerization. TNF-alpha signaled conformation changes at the Bax amino and carboxy termini. Exposure of the Bax amino terminus facilitates E1B 19K-Bax binding, which prevented exposure of the carboxy-terminal Bax Bcl-2 homology region 2 epitope. Inhibition of Bax oligomerization by E1B 19K is an activity that bears striking similarity to the means by which bacterial immunity proteins block pore formation by bacterial toxins which have structural homology to Bax.

Colorectal cancer following tamoxifen therapy for breast cancer (United States)

BACKGROUND

An analysis combining data from several clinical trials has raised concern that tamoxifen therapy may increase the risk of a subsequent colorectal malignancy. We conducted a nested case-control study to test this hypothesis.

METHODS

A cohort of women diagnosed with breast cancer in 1978-1992 was identified from the western Washington population-based cancer registry. Cases included women who subsequently developed colorectal cancer prior to 1995. Controls were a random sample of the cohort who did not develop a second primary malignancy, matched to cases on age, stage, and year of initial cancer diagnosis. Tamoxifen use was ascertained by medical record abstraction and physician questionnaires.

RESULTS

Thirty-six percent of the 122 cases for whom information could be obtained received tamoxifen versus 38% of 194 controls. Relative to non-users and adjusted for receipt of other therapies, there was no increased risk of colorectal cancer associated with tamoxifen use in general (matched odds ratio [mOR] = 0.9, 95% CI 0.6-1.6), longer durations of use (for > or =37 months, mOR = 0.8, 95% CI 0.4-1.9), higher cumulative doses of therapy (for > or =15 g, mOR = 0.8, 95% CI 0.4-1.6), or use that started at least 5 years prior to the end of study follow-up (mOR = 1.1, 95% CI 0.3-3.7).

CONCLUSIONS

We found no overall increased risk for colorectal cancer among tamoxifen users.

Variation in mammographic breast density by race

PURPOSE

Because of the observed racial differences in risk of developing breast cancer, the authors conducted a study to determine the variation in breast density, a strong predictor of breast cancer risk, by race and age.

METHODS

Study subjects were women enrolled in Group Health Cooperative of Puget Sound, Seattle, WA, aged 20-79 years, who had a screening mammogram between 6/1/96 and 8/1/97. Women with increased breast density (BI-RADS "heterogeneously dense" and "extremely dense") (n = 14,178) were compared to those with fatty breasts (BI-RADS "almost entirely fat" and "scattered fibroglandular tissue") (n = 14,323). Logistic regression was used with adjustment for age, parity, age at first birth, menopausal status, current use of hormone replacement therapy, and body mass index.

RESULTS

The odds ratio (OR) for having dense breasts versus fatty breasts, comparing Asian to White women, increased from 1.2 [95% confidence interval (CI) 0.9-1.6] for women age <45 to 1.6 (95% CI 1.3-2.2) for women over 65. Conversely, the OR for Black compared to White women was highest for the women age 65 and younger (OR 1.7 (1.2-2.3), 1.3(1.0-1.7), and 1.7 (1.2-2.3) for women age <45, 46-55, and 56-65, respectively), whereas Black women over 65 had similar density as Whites. Hispanic women had similar density compared to Whites for all ages.

CONCLUSIONS

These racial differences in breast density generally do not conform to differences in race and age-specific breast cancer incidence rates.