A study of the effects on mothers and newborns of breast cancer chemotherapy during pregnancy showed no significant treatment-related differences. The researchers found that adverse outcomes for infants were related to early delivery—usually induced to start breast cancer treatment sooner—not to the cancer or to chemotherapy itself.
European researchers conducted the study, which was published in Lancet Oncology.
Background and Reason for the Study
Between 7 and 15 percent of women under age 40 are diagnosed with breast cancer and may be pregnant at diagnosis.
Women needing chemotherapy were once advised to terminate their pregnancies. Many doctors now recommend using chemotherapy after the first trimester (first three months of pregnancy).
Some pregnancies in women with breast cancer end in premature, or early, delivery. This is especially true for mothers who delay treatment until after their infants are born, so labor is medically induced to shorten time to treatment. Early delivery is known to cause more problems for newborns than full-term delivery.
The study researchers were looking to determine the safety of breast cancer treatment during pregnancy for women and their developing fetuses.
Due to the relative rarity of breast cancer during pregnancy, women from a large area—seven European countries—were recruited. Data about their pregnancies and breast cancer treatment was collected in a registry, which is ongoing.
Over 8-1/2 years, all women registered in the study had a diagnosis of breast cancer during pregnancy. Inclusion was not dependent upon pregnancy outcome or the type or timing of treatment.
The researchers used the data to determine fetal health for up to four weeks after delivery. Factors considered included birth weight and adverse effects. The researchers compared fetal outcomes to chemotherapy exposure. They also measured breast cancer-free survival for the women.
The study looked at 413 women:
- All had early-stage breast cancer
- Median age at diagnosis was 33
- At diagnosis, median gestational age (time since the start of the last menstrual cycle) was 24 weeks
- 197 (48 percent) were treated with chemotherapy during pregnancy
The researchers determined that delay of chemotherapy treatment did not significantly affect disease-free survival for the women. Median breast cancer-free survival was found to be 70.6 months for women receiving chemotherapy during pregnancy, who were more likely to have been diagnosed at a later disease stage. Those who started chemotherapy after delivery had disease-free survival of 94.4 months.
After adjusting for gestational age in the 386 infants delivered, the researchers determined that babies exposed to chemotherapy had lower birth weight. Those infants also had more complications or malformations—occurring more often in those born prematurely, before the 37th week of gestation. The researchers found those complications were mostly due to premature delivery, planned (induced) by providers, and not chemotherapy exposure. (Previous studies show no difference in unplanned premature births between women without cancer and those who receive chemotherapy in the second or third trimester.)
Two infants born early died. One was found to have a chromosome disorder that often results in death. Although both babies had been exposed to chemotherapy, their deaths were not related to treatment.
What This Means for You
The problems infants experienced were likely related to premature delivery, the researchers concluded. They determined that having a full-term delivery was “of paramount importance” for infant health. This finding reinforces those of an earlier study that showed infants whose mothers have chemotherapy during pregnancy do not have treatment-related developmental effects. Negative outcomes were found in some infants born prematurely.
If you are pregnant when diagnosed with breast cancer, this study provides more support for the safety of chemotherapy when given after the first trimester of pregnancy. Treatment during pregnancy also may enable you to deliver full-term, an important factor for newborn health. It’s very important to talk with your doctor about your treatment plan and ways to avoid an early delivery.
You may want to visit Hope for Two…The Pregnant with Cancer Network to connect with other women who have been diagnosed during pregnancy.
S Loibl, SN Han, G von Minckwitz et al. Treatment of Breast Cancer During Pregnancy: An Observational Study. The Lancet Oncology, 2012; 13(9): 887-896.
This article was supported by Cooperative Agreement Number DP11-1111 from The Centers for Disease Control and Prevention. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the Centers for Disease Control and Prevention.