WASHINGTONStudies indicating an increased risk of breast cancer in the years immediately after giving birth were not borne out by an investigation at the Fred Hutchinson Cancer Research Center, Seattle, Linda S. Cook, PhD, reported at the Department of Defenses Era of Hope breast cancer conference. A second study presented at the meeting shows that when breast cancers do occur immediately after childbirth, they are likely to be more severe.
In her presentation, Dr. Cook said that there is no consistent pattern of elevated breast cancer risk for women with recent term pregnancies in any age group.
Dr. Cook and her colleagues did a case-control study of 1,023 women, aged 21 to 45, diagnosed with in situ or invasive breast cancer since 1983 in three counties in western Washington state. They found little association with recent pregnancy and increased risk of developing breast cancer.
Among multiparous women of the same age, parity, and age at first term birth, there was no increased risk for those who had their last birth late in their reproductive life, compared with those who had their last term pregnancy earlier, Dr. Cook said.
More Severe Disease
While Dr. Cook found that there was no greater likelihood of diagnosis in the years right after giving birth, Professor Mads Melbye, of the Danish Epidemiology Science Centre, Copenhagen, said that those women who are diagnosed with breast cancer at that time may have more severe disease.
Dr. Melbyes group looked at records of 5,652 women with breast cancer, aged 45 years or less at the time of diagnosis. The registry included data on reproductive history, tumor size, and nodal status at diagnosis.
A diagnosis of breast cancer within 2 years after birth is associated with particularly poor survival irrespective of the stage of the disease at debut, he said. The difficulty of diagnosing breast cancer in young women in general, and pregnant and lactating women in particular, because of the density of the mammary glands, is reflected in a significant diagnostic delay among these patients.
Prof. Melbye said that the tendency for recently pregnant women to have more advanced disease could, at least to some extent, be caused by delayed diagnosis. However, our detailed information on each womans tumor characteristics allowed us to adjust for this, Prof Melbye said.
Independent of the potential influence of delayed cancer diagnosis, the study showed that a recent birth before the diagnosis of breast cancer conferred an increased risk of dying of the disease of about 60%, compared with the mortality risk of other women with breast cancer.
The negative effect of recent pregnancy was pronounced both in low-risk women who did not receive adjuvant treatment and in high-risk women who did receive adjuvant therapy. Therefore, it is not known whether more intensive adjuvant treatment will change the course of the disease in these patients, Prof. Melbye said, adding that these findings need to be considered in counseling such patients and in deciding on adjuvant treatment.
Prof. Melbye suggests that pregnancy history be recorded for premenopausal breast cancer patients in prospective clinical trials so that response to adjuvant treatment according to time since last childbirth can be assessed.