Estrogen-progestin menopausal hormone therapy associated with high risk of both lobular and tubular breast cancer

Estrogen-progestin menopausal hormone therapy is associated with a more than two-fold higher relative risk of developing lobular cancer or tubular cancer than of developing ductal cancer.

The results of a large European study published in the journal Breast Cancer Research show for the first time that estrogen-progestin therapy is associated with a higher relative risk of developing tubular cancer than ductal cancer, when taken for more than five years. The study also confirms previous findings that estrogen-progestin therapy is associated with a higher relative risk of lobular cancer than ductal cancer.

Lena Rosenberg from the Karolinska Institutet in Stockholm, Sweden and colleagues from the Karolinska Institutet and the Genome Institute of Singapore carried out a population-based case-control study of women recently diagnosed with invasive breast cancer. They selected 1,888 women with ductal breast cancer, 308 women with lobular cancer and 93 women with tubular breast cancer. All women were matched for age with 3,065 women randomly selected from the population, acting as controls. Both patients and controls were asked to fill in a questionnaire about their medical history, health status and use of menopausal hormone therapy.

Rosenberg et al.’s results show that women who used medium potency estrogen-progestin combination therapy had a higher risk of developing lobular or tubular breast cancer than of developing ductal cancer, compared with women who did not use hormone therapy. The risk of developing any of the cancers was higher for women who had used the therapy for more than five years. For these women, the risk of developing tubular cancer (OR 6.5, 95% confidence interval 2.8-14.9) or lobular cancer (OR 5.6, 95% confidence interval 3.2-9.7) was more than twice the risk of developing ductal cancer (OR 2.3, 95% confidence interval 1.6-3.3).

Other factors, such as the number of births, age at menopause or body mass index, were found to be associated with a similar risk of developing the three subtypes of breast cancer.