Oral contraceptive use and abortion before first term pregnancy in relation to breast cancer risk

Abstract

A recent publication from California in this journal has suggested that both prolonged oral contraceptive use and abortion before first term pregnancy increases the risk of breast cancer in young women. Data are presented on 1176 women aged 16-50 years with breast cancer, interviewed in London or in Oxford, together with a like number of matches control subjects. The results are entirely reassuring, being, in fact, more compatible with protective effects than the reverse. Possible reasons for the differences between the 2 sets of data are discussed.

PIP: A 1981 California case-control study on women with breast cancer found oral contraceptive (OC) use for more than 48 months before 1st term pregnancy to be associated with an increase in cancer risk; before 1st term pregnancy abortion, whether spontaneous or induced, was also associated with increased breast cancer risk. This British study with data on 1176 women (16-50 years old) with breast cancer shows no suggestion of association between OC use and breast cancer risk, even in women with more than 48 months of use before the 1st term pregnancy; it found no association between abortion before 1st term pregnancy and cancer risk, either overall or in any of the subgroups defined by age and parity. Married controls matched the women with breast cancer with respect to age, parity, and method of interview. The disparities between the British and California results may be from the combined effect of chance, the selection of available subjects for interview, and differences in the method of analysis. Since the California series related to a population using OC for longer periods than the British series, this study's negative results may carry less weight than indicated.