Dietary factors and epithelial ovarian cancer

Trends in the mortality (1950-1997) and incidence (1975-1993) of malignant ovarian neoplasm among Japanese women: analyses by age, time, and birth cohort

OBJECTIVE

The purpose of this study was to explore epidemiological features of malignant ovarian neoplasm in Japan.

METHODS

The number of deaths from malignant ovarian neoplasm was obtained from the national vital statistics. Estimated incidence rates, based on several cancer registries, were also used for analyses. We divided the subjects into two age groups (0-29 and 30+ years) and examined secular trends in mortality (1950-1997) and incidence (1975-1993) by age, time, and birth cohort.

RESULTS

The age-adjusted mortality rate has increased approximately 4-fold (from 0.9 to 3.6 per 100,000 women) from 1950 to 1997. Age-specific mortality rates showed a rising pattern in the elderly, whereas mortality in the younger people tended to increase in the 1950s and 1960s, but then decreased in the 1970s and afterward. In analyses using a mathematical model, the time effect in the population aged 0-29 years increased with advancing period up to 1970, and then decreased. The cohort effects had positive values, which indicate higher than additive influence from age/time effect, for birth cohorts from 1900 to 1935. The age-adjusted incidence rate increased approximately 1.5-fold (from 3.6 to 5.7) from 1975 to 1993. The rate increased in the early 1980s, but has remained stable since the late 1980s. Age-specific incidence rates in older age groups increased steadily up to 1985, and have remained stable since, while the rates in younger women have remained almost unchanged.

CONCLUSION

The major effects on malignant ovarian neoplasm in Japan are supposed to be due to declining parity and therapeutic improvements.

Diet and ovarian cancer risk: a case-control study in Italy

To assess the dietary correlates of cancer of the ovary, the consumption of a wide range of food groups has been investigated in a case-control study conducted between January 1992 and September 1999 in 4 Italian areas. Cases were 1,031 women with incident, histologically confirmed epithelial ovarian cancer; controls were 2,411 women admitted to the same network of hospitals as the cases for acute, non-malignant and non-gynecological conditions, unrelated to hormonal or digestive tract diseases or to long-term modifications of diet. The subjects' usual diet was investigated through a validated food frequency questionnaire including 78 foods and recipes, then grouped into 18 food groups. Odds ratios (OR), and the corresponding 95% confidence intervals (CI) were estimated using unconditional multiple logistic regression models including terms for age, study center, education, year at interview, parity, oral contraceptive use and energy intake. Significant trends of increasing risk emerged for red meat (OR = 1.53 for the highest compared with the lowest quintile of consumption), whereas inverse associations were observed for consumption of fish (OR = 0.51), raw (OR = 0.47) and cooked vegetables (OR = 0.65), and pulses (OR = 0.77).

Diet and cancer

The large differences in cancer rates among countries, striking changes in these rates among migrating populations, and rapid changes over time within countries indicate that some aspect of lifestyle or environment is largely responsible for the common cancers in Western countries. Dietary fat has been hypothesized to be the key factor because national consumption is correlated with the international differences. However, detailed analyses in large prospective studies have not supported an important role of dietary fat. Instead, positive energy balance, reflected in early age at menarche and weight gain as an adult, is an important determinant of breast and colon cancers, consistent with numerous studies in animals. As a contributor to positive energy balance, and possibly by other mechanisms, physical inactivity has also been shown to be a risk factor for these diseases and in part accounts for the international differences. Although the percentage of calories from fat in the diet does not appear related to risk of colon cancer, greater risks have been seen with higher consumption of red meat, suggesting that factors other than fat per se are important. In many case-control studies, a high consumption of fruits and vegetables has been associated with reduced risks of numerous cancers, but recent prospective studies suggest these associations may have been overstated. Among the factors in fruits and vegetables that have been examined in relation to cancer risk, present data most strongly support a benefit of higher folic acid consumption in reducing risks of colon and breast cancers. These findings have been bolstered by an association between incidence of colon cancer and a polymorphism in the gene for methylenetetrahydrofolate reductase, an enzyme involved in folic acid metabolism. The benefits of folic acid appear strongest among persons who regularly consume alcohol, which itself is associated with risk of these cancers. Numerous other aspects of diet are hypothesized to influence the risks of cancers in Western countries, but for the moment the evidence is unclear.

Anthropometric and other risk factors for ovarian cancer in a case-control study

Because it has been suggested that an environmental factor may play a role in the etiology of ovarian cancer, a case-control study was conducted to assess some environmental and other risk factors for ovarian cancer from 1994 to 1996 in northern Kyushu, Japan. We analyzed the data of 89 cases with epithelial ovarian cancer and 323 controls without any cancer or ovarian disorder. After controlling for the effect of potential confounders, the odds ratios of ovarian cancer across increasing quartiles of the heaviest body weight were 1.00, 1.15, 1.71, 2.29 (P = 0.008, test for trend). Significantly increased risks were noted for a history of diabetes mellitus (P < 0.05), and for a family history of ovarian cancer (P < 0.05). Significantly decreased trends for risk were obtained for the number of pregnancies (P < 0.01) and the number of live births (P < 0.001). This study provides additional support for an association between obesity and the risk of ovarian cancer. This relationship may at least partly explain the recent increase in the incidence of ovarian cancer in Japan, although possible contributions of other factors can not be ruled out.

Ovarian surface epithelium, ovulation and carcinogenesis

It appears that ovarian surface epithelial cells activated by contact with gonadotropin-stimulated preovulatory follicles can release bioactive substances that weaken the tunica albuginea and apical follicular wall (e.g. collagenolytic enzymes) and induce cell death (e.g. apoptotic agents). However, a definitive obligatory role of the ovarian surface epithelium in ovulation remains equivocal. Epithelium exfoliated from the dome of ovulatory follicles is replenished by generative stem cell replication and migration from the wound edges. Mutagenesis has been related to successive bouts of ovulation and mitosis. Common epithelial ovarian cancer is a deadly insidious disease, mainly because it is asymptomatic until the malignancy has reached beyond the ovaries. The most important susceptibility factors are nulliparity and association to an affected first-degree relative. It will be critical to resolve whether parity and oral contraceptive use confer significant protection to women with a family history of ovarian carcinoma. Clearly, innovative approaches to non-invasive screening and treatment are needed. Early detection is the key to saving lives (90% cure by salpingo-ovariectomy alone if diagnosis is at Stage I). Active immunization with defined tumor epitopes or (passive) intraperitoneal administration of effector-functional humanized antibodies may be of special value in the regional management of common epithelial ovarian cancer.

Modulation of colon tumor oncogene expression by cancer patient-derived lipids

In an effort to understand the role of specific fats on carcinogenesis, we have studied the effects of lipids derived from cancer patients on components associated with the regulation of proliferation. The treatment of tumor cells with patient-derived fats produced increased cell proliferation, as indicated by shorter doubling times. The effects of patient-derived lipids on the expression of ras, c-jun, c-erbB-2, and p53 gene products were examined. The cellular expression of the ras proto-oncogene product was increased in both colon tumor cell lines, following lipid treatment. However, c-jun proto-oncogene expression was elevated in HT-29 cells and appeared unchanged in SK-Co-1 cells after lipid treatment. Treatment of HT-29 tumor cells with patient-derived fats produced an enhancement of the p53 gene product, whereas fat treatment reduced p53 expression in SK-Co-1 tumor cells. Further separation of the patient-derived fats indicated that the amplification of p53 gene expression in HT-29 cells could be achieved primarily by addition of the diacylglycerides fraction. Addition of the purified fatty acids, comprising the diglyceride fraction, indicated that the fatty acids, 16:1, 18:0, and 18:1, induced the most significant increases in p53 expression by HT-29 cells. These alterations caused by cancer patient-derived fats are consistent with the loss of normal growth regulation and may explain the epidemiologic association between certain fats and carcinogenesis.

Chlorophyll and chromosome breakage

Increased consumption of green vegetables in the diet has been associated with protection against carcinogenic effects and related mutagenic and clastogenic (chromosome breaking) activity of genotoxic agents. Chlorophyll, present in all green plant parts, has been suggested to be a major protective factor in the process. We have, however, observed that while a crude aqueous extract of Indian spinach leaf significantly reduced genotoxic effects, chlorophyll alone was ineffective. On the other hand, chlorophyll, both as an aqueous extract from the leaf and in a purified commercial form, induced a significantly high frequency of chromosome breaks in bone marrow cells of mice on oral administration. The crude aqueous extract of the leaf was non-toxic. The protective activity of the crude leaf extract may be attributed to the total effect of the interaction between different components, in which the clastogenicity of chlorophyll has been neutralized.

Is tubal sterilization associated with an increased risk of subsequent hysterectomy but a decreased risk of ovarian cancer? A review of recent literature

Recent epidemiologic studies have suggested that tubal sterilization (TS) may lead to an increased incidence of subsequent hysterectomy but a decreased risk of ovarian cancer. This review evaluates the nature and magnitude of these two relationships, which should be of great concern and interest to women, clinicians and the administrators of family planning programs. The positive relationship between TS and subsequent hysterectomy is more likely to be of a motivational rather than biological nature, and a considerable number of unnecessary hysterectomies after TS could be avoided by changing the attitudes of physicians and women. The inverse relationship between TS and ovarian cancer appears causal, although the exact biological mechanisms remain to be clarified. Theoretically, this non-contraceptive beneficial effect of TS could be used as a primary preventive measure to curb the incidence of the highly fatal ovarian cancer. However, a number of medical, ethical, and economic questions attending use of a generally irreversible contraceptive procedure as a preventive measure must first be answered. The issue of whether TS is associated with any long-term sequelae, and, if so, whether the association is of a cause-and-effect nature or a by-product of time passage and aging of the woman, should be addressed by well-designed studies.

Chlorophyll and chlorophyllin as modifiers of genotoxic effects

Reports on an inverse relationship between the consumption of fresh vegetables and human gastrointestinal cancer have been followed by screening for the protective activity of a large number of plant extracts, including leafy vegetables. Chlorophyll is ubiquitous in all green plant parts. Chlorophyllins are derivatives of chlorophyll in which the central magnesium atom is replaced by other metals, such as cobalt, copper or iron. An attempt has been made in this article to review the relative efficacy of chlorophyll and chlorophyllin in modifying the genotoxic effects of various known toxicants.

Dietary lactose intake, lactose intolerance, and the risk of epithelial ovarian cancer in southern Ontario (Canada)

A case-control study of dietary factors and cancer of the ovary was conducted during 1989-92 in metropolitan Toronto and surrounding areas of southern Ontario, Canada. Four hundred and fifty women aged 35-79 years, with newly diagnosed, histologically verified, primary epithelial ovarian-cancer were interviewed concerning reproduction and diet. Over the same period, 564 randomly-selected population controls, frequency-matched to the cases within three 15-year age groups, also were interviewed. From information obtained by quantitative diet history, average daily macro- and micronutrient intake values were calculated through use of the United States Department of Agriculture Food Composition Databank, which was extended and modified for Canadian items and recipes. Analysis was performed with continuous, unconditional logistic-regression methods, adjusting for age at interview, number of full-term pregnancies, total duration of oral contraceptive use, and total daily caloric intake. Neither reported history of lactose intolerance, nor average daily consumption of lactose or free galactose, were found to be associated with risk of ovarian cancer. Lactose intake or intolerance did not appear to modify the protective effects of parity and oral contraceptive use. Nevertheless, other studies suggest that ovarian galactose metabolism still may have a relationship with risk of ovarian cancer, though more evidence is needed.

Etiology, biology, and epidemiology of ovarian cancer

Epithelial ovarian cancer kills more women per year than all other gynecologic cancers combined. Pregnancy, oral contraceptive use, and tubal ligation decrease the risk of the disease, whereas risk is increased for women whose family history is consistent with one of the familial ovarian cancer syndromes. Several theories have been postulated concerning the etiology of ovarian cancer, including the incessant ovulation theory and that based on the model of hypergonadotropic hypogonadism. Chromosomal abnormalities and allele losses have been described in ovarian cancers. Involvement of oncogenes and tumor suppressor genes has been investigated as well. Genetic linkage studies are ongoing in families whose history is consistent with one of the familial ovarian cancer syndromes.

Relationship between Quetelet's index and cancer of breast and female genital tract in 47,000 women followed for 25 years

The relationship between Quetelet's index and subsequent risk for cancer of endocrine target organs was studied in a cohort of 47,003 women, examined for height and weight in the years 1963-65, and followed up in the Swedish Cancer Register until 1987. High Quetelet's index was associated with a decreased risk for breast cancer among women less than 55 years of age at risk, while a high Quetelet's index predicted an increased risk among older women. Among women > or = 55 years of age, the excess relative risk for breast cancer associated with high Quetelet's index declined significantly during the follow-up period. Cancer of the ovaries and the uterine cervix were not significantly related to Quetelet's index in any age group. In women > or = 55 years of age, the relative risk for cancer of the uterine corpus associated to Quetelet's index was higher than that for breast cancer, and this association persisted during the entire follow-up period of more than 20 years. In spite of the fact that endometrial cancer is less common than breast cancer, because of the stronger relation between overweight and endometrial cancer, more endometrial cancer would be attributable to obesity than breast cancer.

Diet and ovarian cancer: a case-control study in Greece

In a hospital-based case-control study of common malignant epithelial tumors of the ovary, conducted in Athens (1989-1991), 189 cases were compared with 200 hospital visitor controls. Personal interviews were conducted in all cases and diet was ascertained through a semi-quantitative food frequency questionnaire. Nutrient intakes for individuals were estimated by multiplying the nutrient content of a typical portion size for each specified food item by the frequency at which the food was consumed per month and summing these estimates for all food items. Data were analyzed using logistic regression, controlling for non-dietary confounding factors, total energy intake and, among nutrients, mutual confounding influences. Adjusted odds ratios (rate ratios) for ovarian cancer, associated with particular nutritional variables, were expressed in terms of increments approximately equal to the standard deviations of (the residual of) the respective nutrients, on a daily basis. The adjusted odds ratios (and 95% confidence intervals) were 0.80 (0.65-0.99) for mono-unsaturated fat and 0.73 (0.61-0.87) for crude fiber. No substantial, statistically significant or consistent independent associations were noted for total energy, total protein, saturated fat, polyunsaturated fat, dietary cholesterol, total carbohydrates, sucrose, vitamin C, vitamin A, riboflavin or calcium. These associations, if causal, could explain to some extent the relatively low incidence of ovarian cancer in Greece and other Mediterranean countries as well as the increasing incidence trends noted in these countries during the last few decades.

Incidence trends for cancers of the breast, ovary, and corpus uteri in urban Shanghai, 1972-89

Incidence data from the Shanghai (People's Republic of China) Cancer Registry were used to assess the temporal trends of three major female cancers during 1972-89. Rates for cancers of the breast, corpus uteri and, to a lesser extent, ovary rose over the study period. The increases in breast and ovarian cancer were most pronounced among women under age 50, whereas those for corpus uteri cancer were restricted generally to those aged 55 to 69 years. When considered by cohort year of birth, risk of breast and ovarian cancers rose among women born since 1925 and 1935, respectively, but little evidence of cohort effect was apparent for corpus uteri cancer. Potential explanations for these patterns are explored.

Occupational physical activity and the incidence of cancer of the breast, corpus uteri, and ovary in Shanghai

BACKGROUND

A sedentary life style has been consistently associated with an increased risk of colon cancer, but the evidence for its association with breast and other gynecologic cancers is limited.

METHODS

Occupational information for 3783 incident patients with cancer (breast, 2736; corpus uteri, 452; and ovary, 595) whose disease was diagnosed during the period 1980-1984 was compared with 1982 census data on employment in Shanghai urban areas. The standardized incidence ratios (SIR) of these cancers were estimated for each occupational group classified by job titles and physical activity levels.

RESULTS

A significantly increased incidence of breast cancer was found among professionals (SIR = 158), government officials (SIR = 131), and clerical workers (SIR = 143); the incidence was reduced among service workers (SIR = 87) and craftsmen (SIR = 91). Occupational physical activity, as measured by sitting time and energy expenditure, was inversely related to breast cancer incidence, with SIR of 127-131 for inactive jobs (sedentary or low-energy expenditure) and 79-93 for active jobs (long periods of standing or high energy expenditure). Similar associations, although to a lesser extent, were also seen for cancer of the corpus uteri and ovary.

CONCLUSIONS

Women with low physical activity occupations had an increased incidence of cancer of the breast, corpus uteri, and ovary; the incidence was reduced among women with high-activity jobs. These findings were consistent with observations from earlier studies and provided further evidence that physical activity may lower the risk of these female hormone-dependent cancers.

Cancer incidence trends in urban Shanghai, 1972-1989

Incidence data pertaining to more than 250,000 cancer cases diagnosed during the years 1972-1989 among residents of urban Shanghai, China, were analyzed to determine the relative importance of the various malignancies and to discover changes over time. In the most recent 3-year period, lung cancer was the most frequent cancer among men (57.0 per 100,000 person-years, age-adjusted world standard), followed by cancers of the stomach (50.1), liver (29.6), esophagus (13.3), colon (11.2) and rectum (9.4). Among women, breast cancer leads (25.1), followed by cancers of the stomach (23.2), lung (18.8), liver (10.9), colon (10.2) and rectum (7.3). The most impressive increases in incidence rates from 1972-74 to 1987-89 were observed for cancers of the gallbladder (119% and 101% among men and women, respectively), colon (85% and 78%), and brain and other nervous system (71% and 60%). In addition, increases of 20-50% occurred for cancers of the pancreas, male lung, female breast, corpus uteri, kidney, and for non-Hodgkin's lymphoma. Rates declined notably for cancers of the esophagus (-54% and -53%), cervix uteri (-86%), and to a lesser extent (10-20%) cancers of the male stomach and liver. These observed trends can be explained only partly by improvements in cancer diagnosis and completeness of the cancer registry, and most likely reflect changes in the prevalence of risk factors in this population.

Fruit, vegetables, and cancer prevention: a review of the epidemiological evidence

Approximately 200 studies that examined the relationship between fruit and vegetable intake and cancers of the lung, colon, breast, cervix, esophagus, oral cavity, stomach, bladder, pancreas, and ovary are reviewed. A statistically significant protective effect of fruit and vegetable consumption was found in 128 of 156 dietary studies in which results were expressed in terms of relative risk. For most cancer sites, persons with low fruit and vegetable intake (at least the lower one-fourth of the population) experience about twice the risk of cancer compared with those with high intake, even after control for potentially confounding factors. For lung cancer, significant protection was found in 24 of 25 studies after control for smoking in most instances. Fruits, in particular, were significantly protective in cancers of the esophagus, oral cavity, and larynx, for which 28 of 29 studies were significant. Strong evidence of a protective effect of fruit and vegetable consumption was seen in cancers of the pancreas and stomach (26 of 30 studies), as well as in colorectal and bladder cancers (23 of 38 studies). For cancers of the cervix, ovary, and endometrium, a significant protective effect was shown in 11 of 13 studies, and for breast cancer a protective effect was found to be strong and consistent in a meta analysis. It would appear that major public health benefits could be achieved by substantially increasing consumption of these foods.

Early detection of ovarian cancer: background, rationale, and structure of the Yale Early Detection Program

Ovarian cancer has received national attention as a highly virulent disease. Its lack of early warning symptoms and the failure to develop highly sensitive screening tests have led some physicians to recommend prophylactic oophorectomies to women with relatives who have had ovarian cancer. Others have recommended routine screening of otherwise normal women for CA 125, a circulating tumor marker, and ultrasound examinations. Each of these techniques is associated with substantial false-positive rates that could lead to unnecessary surgery. A review of epidemiologic data suggests that familial ovarian cancer kindreds are rare, but women with first-degree relatives who have had ovarian cancer have a significant risk themselves for developing ovarian cancer. In addition, women with a great number of ovulatory cycles are at an increased risk for the disease. Circulating tumor markers are frequently elevated in women with advanced ovarian cancer, but their value in early detection of ovarian cancer has yet to be established. Advances in endovaginal ultrasound and color Doppler flow technology have significantly improved our ability to assess pelvic organs. This article presents the background, rationale, and structure of the Yale Early Detection Program for ovarian cancer, whose goals are to identify the best techniques for diagnosing ovarian cancer in an early stage, to determine the frequency with which such tests should be employed, to assess false-positive results, and to identify women who might benefit from prophylactic oophorectomies.

Dietary fat and cancer: consistency of the epidemiologic data, and disease prevention that may follow from a practical reduction in fat consumption

International variations and national time trends in disease rates suggest major associations between dietary fat and several important cancers. In contrast, case-control and cohort studies of dietary fat in relation to the same cancers generally report weak associations, or have failed to detect any association with fat intake. This study was undertaken in an attempt to understand the apparent discrepancy between these observations. The results provide an insight into the magnitude of cancer risk reduction that may follow from a practical reduction in dietary fat. Regression analyses of international variations in cancer incidence rates were used to estimate relative risks (RR) as a function of fat intakes for both males and females. These analyses focused on cancers of the breast, colon, rectum, ovary, and endometrium in females, and colon, rectum, and prostate cancers in males. Ages 55-69 and 30-44 were considered in order to compare RR estimates between an older and younger age group, and between post- and pre-menopausal women. Corresponding RR estimates were also calculated, based on the regression of changes in disease rates from the mid-1960s to 1980 on changes in dietary fat, using data from several countries. A strong degree of consistency with the RR estimates from international comparisons was observed. The international regression analyses were also used to project changes in cancer rates among Japanese migrants to the United States. A high level of consistency with the observed disease-rate changes was noted. Similarly, the international data analyses were used to project RRs for the fat intake categories used in specific case-control and cohort studies, while acknowledging measurement error in individual dietary assessment. Although certain exceptions are noted, considerable consistency was found between the aggregate and analytic data results, leaving open the strong possibility that a practical reduction in dietary fat could result in a major reduction in the incidence of several prominent cancers in the United States and in other nations having high fat consumption.

Nutritional factors and cancers of the breast, endometrium and ovary

From an overview of epidemiological evidence on nutrition, diet and cancers of the breast, endometrium and ovary, the following indications can be drawn: Overweight and obesity are causally related to endometrial and post-menopausal breast cancer, and may account for as much as one third of the cases of endometrial and one tenth of breast cancer in Europe. It is not known whether obesity or overweight early in life has any role on breast cancer risk, nor whether obesity influences ovarian carcinogenesis. Overweight tends to be associated with an unfavourable prognosis for breast cancer. Despite extensive research, the available knowledge on diet and breast cancer is largely inconsistent, and the results from ecological and individual-based studies are contradictory in relation to fat, proteins, total energy, alcohol, etc. There are only scanty data on diet and endometrial or ovarian cancer, which tend to suggest role for fat (or animal fat) in the risk of these neoplasms. The evidence on diet and breast, ovarian and endometrial carcinogenesis is still too scanty or inconsistent to be of any practical preventive value. Thus, the only clear indication for prevention is that a reduction of overweight would avoid a substantial number of cases of endometrial and post-menopausal breast cancer.