Pregnant women who develop breast cancer should continue the pregnancy and be treated as closely as possible to standard recommendations for nonpregnant women, data from a prospective and retrospective registry has shown.

While fetal and breast cancer outcomes were comparable between those who received chemotherapy during pregnancy compared with those who waited until after delivery for treatment, the latter had more premature deliveries, leading to an increased risk of fetal morbidity and an unfavorable long-term outcome, investigators concluded during the 33rd Annual CTRC-AACR San Antonio Breast Cancer Symposium.

Dr. med. Sibylle Loibl of the German Breast Group, Neu-Isenburg, Germany, reported results of 313 patients with breast cancer during pregnancy. Primary end point was fetal outcome 4 weeks after delivery. Secondary end points included maternal outcome of pregnancy, stage at presentation and biological characteristics, breast cancer therapy and type of surgery, mode of delivery (vaginal vs cesarean), outcome of the newborn 5 years postdiagnosis, and outcome of breast cancer 5 years after diagnosis.

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Of the 260 women who continued pregnancy (two infants died shortly after birth and 29 women had an abortion or miscarriage), 142 received chemotherapy during pregnancy. Gestation at diagnosis was 20 weeks in those who received chemotherapy (n = 142) and 28 weeks in those who received chemotherapy postdelivery (n = 118). Week of delivery and birth weight were comparable between the two groups; however, percentage of deliveries before the 35th week was significantly higher in those who received chemotherapy after delivery (33% vs 16.9%; P = 0.009).

Dr. Loibl said premature deliveries were most likely to allow for an early treatment start. Infants from both groups experienced congenital problems, which are “about 1 to 3 percent in the general population, but was higher in this cohort.”

Although incidence of pregnancy among breast cancer patients is small (about 2%-3%), women are delaying childbirth until a later age, which may increase cases of breast cancer among pregnant women, Dr. Loibl said. All women were pregnant when they were diagnosed with cancer: 23% in the first trimester, 42% in the second, and 36% in the third. Median overall disease-free survival of the mothers was 27 months and median overall survival, 55 months.