Clair Chilvers

EFFECT OF AGE AT ORCHIDOPEXY ON RISK OF TESTICULAR CANCER

69 (9.5%) of 724 patients with testicular cancer first seen at the Royal Marsden Hospital over the 10-year period 1975 to 1984 had a history of cryptorchidism. 11 patients had an uncorrected undescended testis when their testicular cancer was diagnosed, and 58 had had an orchidopexy or an orchidectomy for undescended testis. There are no general population data with which to compare the 15.9% (11/69) of testicular cancer patients with uncorrected cryptorchidism. However, the distribution of age at orchidopexy (or orchidectomy) of the 58 patients treated for undescended testis was almost identical to that expected on the basis of national rates. The age at treatment of undescended testis appears to have no effect on the risk of testicular cancer.

DOES PREGNANCY PROTECT AGAINST OVARIAN CANCER

A clear inverse relation between average completed family size and mortality from ovarian cancer in different populations of women is seen from one country to another; for successive generations of women living within the same country; in married and single women; and in different social, religious, immigrant, and ethnic groups. The findings suggest that pregnancy--or some component of the child-bearing process--protects directly against ovarian cancer. This protection seems to persist throughout life. The more-than-twofold increase in the age-standardised ovarian-cancer death-rate in England and Wales since 1931 can be explained largely by changes in the average completed family size.

Health aspects of nitrate in drinking water

Abstract This paper reviews the health aspects of nitrate in drinking water with particular reference to methaemoglobinaemia and carcinogenic risk. It examines regional trends in gastric cancer mortality in England and Wales in relation to nitrogenous fertiliser usage, and mortality from gastric cancer in rural districts in eastern England in relation to nitrate concentrations in public water supplies.

On the estimation of relative risk from vital statistical data.

A method is described for the determination of a measure of relative risk from vital statistical data. If the frequency of disease in a population is linearly related to the level of exposure to a given factor, then a measure of the relative risk can be estimated from the slope and intercept of the regression line. For example, when the exposure is measured in terms of the proportion of the population exposed to the factor, then the relative risk is equal to (Formula: see text). This offers an indirect but simple and inexpensive method for estimating relative risk. It should be used with caution, particularly where confounding factors may be responsible for the apparent association between disease and factor. Applications of the method to estimate the relative risk of (a) circulatory diseases in women using oral contraceptives and (b) ovarian cancer in women with different average family sizes, both yielded relative risk estimates comparable with those obtained from case-control and prospective studies.

Alcohol and oesophageal cancer: an assessment of the evidence from routinely collected data.

Although various factors have been implicated in the aetiology of oesophageal cancer, one factor common to many countries is the consumption of alcoholic beverages. In England and Wales mrtality from oesophageal cancer declined rapidly during the early part of this century but both mortality and incidence have increased in recent years. The generation of males born in 1906 had lower mortality than any preceding or succeeding generation. It is suggested that ages 20 to 30 may be critical in the development of oesophageal cancer and that the 1906 cohort was less exposed to alcohol than other generations. The international analysis suggests that ethyl alcohol itself rather than any specific alcoholic beverage is associated with this cancer.

Oral contraceptive use and breast cancer risk in young women: subgroup analyses

Abstract The UK National Case-Control Study Group reported an increased risk of breast cancer associated with oral contraceptive (OC) use in women in whom the disease was diagnosed before the age of 36. In further analyses to ascertain whether any subgroup is at particularly increased risk, women were grouped by age at diagnosis, reproductive history, personal habits and characteristics, family history of breast cancer, and history of biopsy for benign breast disease; these subgroups were also defined by overall risk score. There was little evidence of altered risk in relation to subgroups: women with a family history of breast cancer had a slightly greater risk associated with OC use than those without, but the difference in trends was not significant.

Further results from a census based mortality study of fertiliser manufacturers.

The results of a further follow up of two cohorts of men identified as manufacturers of fertilisers in the 1961 and 1971 censuses of England and Wales are reported. Both cohorts have now been followed up until 1985 through the National Health Service Central Register. In the 1961 cohort the previous findings are replicated--low mortality from all causes, all cancers, and all circulatory diseases, and no evidence of dose response relation nor excess mortality from cancer at any site. In the 1971 cohort there remain more deaths from cancer than expected but none of the observed deaths from individual cancers differs significantly from expectation by comparison with national mortality rates or rates for other employed men. Evidence of an association between cancer mortality and frequency of exposure to nitrate containing dust is strengthened in the reanalysis of the 1971 cohort after longer follow up, but a negative trend, significant for digestive organ cancers, is observed in the analysis by product type in which manufacturers of straight nitrogen and compound fertilisers might have been expected to be most at risk. Failure to find specifically any excess mortality from gastric cancer and the contradictory dose response relations, weigh against the notion that the nonsignificant excesses of cancers in the 1971 cohort are related to nitrate exposure.

Cancer mortality in England in relation to levels of naturally occurring fluoride in water supplies.

Sixty-seven small areas in England have been classified into four groups according to the level of naturally occurring fluoride in their water supplies. Small area mortality statistics for 1969-73 have been used to look for differences in cancer mortality in relation to fluoride levels. Deaths from all cancers and from cancer at 12 specific body sites have been examined; no consistent trends in mortality are apparent. These results provide no evidence of a harmful effect of naturally occurring fluoride in water supplies.

Stress and cancer surveys: attitudes of participants in a case-control study.

STUDY OBJECTIVE--The aim was to ascertain whether personal interviews carried out for cancer case-control studies cause stress to participants. DESIGN--Retrospective postal questionnaires were sent to women at least three months after interview for a case-control study of the aetiology of cervical cancer. The questionnaire covered attitudes to taking part in the study, stress engendered by participation, whether any particular questions were distressing, factors relevant to the decision to participate, and the role of their doctor with respect to participation. SETTING--South East and South West Thames health regions, United Kingdom. PATIENTS--Patients were women aged 20-45 years at diagnosis with invasive cervical cancer, and population based controls. MEASUREMENTS AND MAIN RESULTS--The response rate was 90%. Nearly all respondents were glad they had participated, while only 2/226 regretted taking part. Half the respondents (115/226) perceived some actual benefit from taking part. The interview carried out in the case-control study was both long and detailed and included topics such as numbers of sexual partners and history of sexually transmitted diseases. As expected, the questions causing most concern to interviewees were those on number of sexual partners, but only 13% of participants were bothered by these questions and only 4% felt inclined to terminate the interview early. CONCLUSIONS--The lack of evidence of stress caused by this potentially difficult interview suggests that, in the hands of experienced interviewers, stress is unlikely to be caused by participation. Many participants felt that they had benefited from taking part. Doctors and ethics committees should find these results reassuring.

Cancer mortality by site and fluoridation of water supplies.

Site-specific cancer mortality data for 20 United States cities have been abstracted from United States Government publications to explore further the hypothesis that fluoridation of water supplies causes cancer. Changes in mortality (standardised for age, sex, and ethnic group) between 1958-62 and 1968-72 in 10 fluoridated and 10 non-fluoridated United States cities have been examined. Of the seven sites (or groups of sites) examined, for only one is there a statistically significant difference between the fluoridated and non-fluoridated cities with respect to average change in mortality. This difference, for cancers of the genital organs, favours the fluoridated cities. These data do not provide evidence of a positive association between fluoridation of water supplies and cancer of any of the sites considered.