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Background. The Collaborative Group on Hormonal Factors in Breast Cancer has brought together and reanalysed about 90% of the worldwide epidemiological evidence on the relation between risk of breast cancer and use of hormone replacement therapy (HRT). Methods. Individual data on 52,705 women with breast cancer and 108,411 women without breast cancer from 51 studies in 21 countries were collected, checked, and analysed centrally. The main analyses are based on 53,865 postmenopausal women with a known age at menopause, of whom 17,830 (33%) had used HRT at some time. The median age at first use was 48 years, and 34% of ever-users had used HRT for 5 years or longer. Estimates of the relative risk of breast cancer associated with the use of HRT were obtained after stratification of all analyses by study, age at diagnosis, time since menopause, body-mass index, parity, and the age a woman was when her first child was born. Findings. Among current users of HRT or those who ceased use 1-4 years previously, the relative risk of having breast cancer diagnosed increased by a factor of 1.023 (95% CI 1.011-1.036; 2p = 0.0002) for each year of use; the relative risk was 1.35 (1.21-1.49; 2p = 0.00001) for women who had used HRT for 5 years or longer (average duration of use in this group 11 years). This increase is comparable with the effect on breast cancer of delaying menopause, since among never-users of HRT the relative risk of breast cancer increases by a factor of 1.028 (95% CI 1.021-1.034) for each year older at menopause. 5 or more years after cessation of HRT use, there was no significant excess of breast cancer overall or in relation to duration of use. These main findings did not vary between individual studies. Of the many factors examined that might affect the relation between breast cancer risk and use of HRT, only a woman's weight and body-mass index had a material effect: the increase in the relative risk of breast dancer associated with long durations of use in current and recent users was greater for women of lower than of higher weight or body-mass index. There was no marked variation in the results according to hormonal type or dose but little information was available about long durations of use of any specific preparation. Cancers diagnosed in women who had ever used HRT tended to be less advanced clinically than those diagnosed in never-users. In North America and Europe the cumulative incidence of breast cancer between the ages of 50 and 70 in never-users of HRT is about 45 per 1000 women. The cumulative excess numbers of breast cancers diagnosed between these ages per 1000 women who began use of HRT at age 50 and used it for 5, 10, and 15 years, respectively, are estimated to be 2 (95% CI 1-3), 6 (3-9), and 12 (5-20). Whether HRT affects mortality from breast cancer is not known. Interpretation. The risk of having breast cancer diagnosed is increased in women using HRT and increases with increasing duration of use. This effect is reduced after cessation of use of HRT and has largely, if not wholly, disappeared after about 5 years. These findings should be considered in the context of the benefits and other risks associated with the use of HRT.

Objective: To investigate the use of digital rectal examination and prostate specific antigen (PSA) testing in a population-based sample of men in New Zealand. Methods: A random selection of men aged 40–74 years, weighted by age, was chosen from the general electoral roll of New Zealand. Only men with a telephone who had been married at some time were eligible. Telephone interviews were conducted using a standard questionnaire. Crude and age-adjusted proportions were calculated. Logistic regression was used to explore associations between socio-demographic factors and digital rectal examination or PSA testing. Results: Interviews were completed for 85% of the 1,486 eligible men and analyses were confined to the 1,225 European men. Many more men reported having a digital rectal examination (41%; 95% CI 33.8–48.2) than a PSA test (9%; 95% CI 4.2–14.2). Men in the lowest social class were significantly less likely to have had a digital rectal examination (OR 0.30; 95% CI 0.18–0.50) or PSA test (OR 0.25; 95% CI 0.11–0.60) compared with those in the highest social class. Men with vocational training or no post-school qualifications were approximately half as likely to report a digital rectal examination or a PSA test compared with men with degrees or diplomas. Conclusions: Although current New Zealand recommendations are that population screening for prostate cancer should not be introduced, many men are still having digital rectal examinations and PSA tests in the absence of symptoms. The frequency of PSA testing is considerably lower than in Australia and appears to be largely influenced by a man's social class.

A nationwide case-control study was conducted in New Zealand, to test hypotheses about the role of infections in the aetiology of childhood leukaemia. Children aged 0–14 years with leukaemia were matched on age and sex to controls selected from birth records. Case ascertainment was virtually complete and 121 (92%) of 131 eligible case families took part. The participation rate among the 303 first-choice eligible controls was 69%. Home interviews and serological tests were conducted. Adjusted relative risks were estimated by logistic regression. There was an increased risk of leukaemia in relation to reported influenza infection of the child during the first year of life (adjusted odds ratio 6.8, 95% confidence interval 1.8–25.7). This could be a chance finding due to multiple comparisons, and it should be tested elsewhere. Some key variables relevant to Greaves' hypothesis were not associated with B-cell precursor acute lymphoblastic leukaemia (numbers of infections and vaccinations, firstborn status, attendance at preschool groups), although a small effect could not be ruled out with a study of this size. Leukaemia risk was higher among children in poorer social circumstances, and this was true for all eligible children as well as for the participants. © 1999 Cancer Research Campaign

The International Collaboration of Epidemiological Studies of Cervical Cancer has combined individual data on 11,161 women with invasive carcinoma, 5,402 women with cervical intraepithelial neoplasia (CIN)3/carcinoma in situ and 33,542 women without cervical carcinoma from 25 epidemiological studies. Relative risks (RRs) and 95% confidence intervals (CIs) of cervical carcinoma in relation to number of full-term pregnancies, and age at first full-term pregnancy, were calculated conditioning by study, age, lifetime number of sexual partners and age at first sexual intercourse. Number of full-term pregnancies was associated with a risk of invasive cervical carcinoma. After controlling for age at first full-term pregnancy, the RR for invasive cervical carcinoma among parous women was 1.76 (95% CI: 1.53-2.02) for > or => or =7 full-term pregnancies compared with 1-2. For CIN3/carcinoma in situ, no significant trend was found with increasing number of births after controlling for age at first full-term pregnancy among parous women. Early age at first full-term pregnancy was also associated with risk of both invasive cervical carcinoma and CIN3/carcinoma in situ. After controlling for number of full-term pregnancies, the RR for first full-term pregnancy at age or => or =25 years was 1.77 (95% CI: 1.42-2.23) for invasive cervical carcinoma, and 1.78 (95% CI: 1.26-2.51) for CIN3/carcinoma in situ. Results were similar in analyses restricted to high-risk human papilloma virus (HPV)-positive cases and controls. No relationship was found between cervical HPV positivity and number of full-term pregnancies, or age at first full-term pregnancy among controls. Differences in reproductive habits may have contributed to differences in cervical cancer incidence between developed and developing countries.

In a prospective study of 43,117 people, prescriptions issued by general practitioners over two years were linked with records of hospital admissions and deaths. For 57 people injured or killed while driving cars, motorcycles, or bicycles the medicines that had been dispensed in the three months before were compared with those dispensed for 1,425 matched controls. There was a highly significant association between use of minor tranquillisers and the risk of a serious road accident (relative risk estimate 4.9). the increased risk of accidents to drivers given tranquillisers could be due to the known psychomotor effects of these drugs or to effects of the conditions being treated. Whatever the reason, patients taking drugs such as diazepam should be warned that they are at special risk.

In a population based case-control study 433 New Zealand women aged 25-54 with newly diagnosed breast cancer were compared with 897 women selected at random from the electoral rolls. The relative risk of breast cancer in women who had ever used oral contraceptives was 0.94 (95% confidence interval 0.70 to 1.25). The relative risk in women aged 25-34 at diagnosis was estimated to be 2.2 (95% confidence interval 0.47 to 9.9) and in older women less than 1. Analyses of risk by duration of use of oral contraceptives, age at first use, and time since first use showed no adverse effect of the pill. In particular, there was no increased risk in women who had used oral contraceptives before the age of 25 or before their first pregnancy, even for prolonged periods. Given the high prevalence of use in New Zealand, this study provides strong evidence against the hypothesis that use of oral contraceptives at young ages increases the risk of breast cancer.