Sex hormones and gynaecological cancer.

The opportunities for preventing cancer of the sex organs in women tend to be very different from those arising with other cancers': for instance, avoidance of sexual intercourse would probably almost eliminate carcinoma of the cervix.2 Even, however, with the current fashion for extrauterine fertilisation coital abstinence will never become an acceptable prophylactic, but further research stimulated by the epidemiological findings may lead to more practicable approaches.3 With cancers of the breast, ovary, and endometrium sexual activity (in so far as it is measured by numbers of pregnancies) appears to be protective. The action may be hormonally mediated, and of these cancers endometrial carcinoma has the clearest endocrine relation: oestrogens unopposed by pro-gestogens predispose to it, while progestogens can inhibit established tumours and may also act prophylactically. A recent report4 suggests that the progestogen in oral contraceptives may have such a protective effect; the numbers were small and analysis of the total data gave results that did not reach statistical significance, but the calculated relative risk of 0 44 is in keeping with other estimates.5 6 Apart from comparison with controls, the pattern of the data is persuasive: protection appears greater with use for over five years, with recent use, and with more progestogenic preparations. This last trend matches the observation that sequential oral contraceptives (in which only some of the tablets taken each month contain progestogen) have been associated with a higher incidence of endometrial cancer than combined preparations.7 A cancer-prevention programme based on long-term manipulation of the "milieu interieur" of a large proportion of the population would be socially unacceptable. Since, however, oral contraceptives produce such a change and are widely used, minor modifications of regimens should be examined in the hope of enhancing any cancer-inhibiting effect without increasing their adverse effects. The sequential regimen seems not to protect against endometrial cancer, while combined oestrogen and progestogen for 21 out of 28 days may give some protection; so daily progestogen alone may be more protective. It was only because regular menstruation was regarded as a natural phenomenon that the regimen for oral contraceptives was designed to simulate this pattern. In reality, given uninhibited sexual activity without contraception and uninhibited lactation after delivery, menstruation is rare. Manipulation of the female sexual cycle did not begin with Pincus and his pill: in the Western world cyclic menstruation became established as a consequence of adoption of Judaeo-Christian sexual mores. The other …