Breast cancer survivors are less likely to get pregnant and have higher risks of some delivery and fetal complications, according to a meta-analysis reported at the 2020 San Antonio Breast Cancer Symposium.
Dr. Matteo Lambertini
However, the data also showed that pregnancy does not increase the risk of cancer recurrence.
“With the availability of more effective anticancer treatments, survivorship and addressing the treatments’ potential long-term toxicities has gained substantial attention,” said study investigator Matteo Lambertini, MD, PhD, of University of Genova (Italy) – IRCCS Policlinico San Martino Hospital.
“Returning to a normal life after cancer diagnosis and treatment should be considered, in the 21st century, as a crucial ambition in cancer care,” Dr. Lambertini added. “In patients diagnosed during their reproductive years, this includes the possibility to complete their family planning. Due to the constant rise in age at first pregnancy over the past years, many women are diagnosed with breast cancer before completing their reproductive plans.”
In that context, certain cancer treatments have the potential to reduce fertility. In addition, many women need prolonged hormone therapy, and conception is contraindicated while they are receiving it.
Study results
Dr. Lambertini and colleagues performed a meta-analysis using data from 39 studies that included a total of 114,573 breast cancer patients and 8,093,401 women from the general population.
Results showed that breast cancer survivors were much less likely than women in the general population to become pregnant (relative risk, 0.40; P < .001).
However, “the majority of the studies included in our meta-analysis did not capture the information on how many women tried to get pregnant,” Dr. Lambertini cautioned.
In the few studies that did, more than half of women trying to conceive did become pregnant, and most of them were able to do so naturally, without need for assisted reproductive technologies.
On the flip side, analyses also showed that pregnancies occurred in some women who did not want to conceive, underscoring the importance of comprehensive oncofertility counseling that addresses not only fertility preservation, but also contraception, Dr. Lambertini said.
Among women who became pregnant, breast cancer survivors did not have higher odds of spontaneous abortion or complications such as preeclampsia, and their infants were not significantly more likely to have congenital abnormalities.
However, the breast cancer survivor group did have higher odds of cesarean birth (odds ratio, 1.14; P = .007), low birth weight (OR, 1.50; P < .001), preterm birth (OR, 1.45; P = .006), and infants small for gestational age (OR, 1.16; P = .039).
In stratified analysis, the higher risk of having an infant with low birth weight was significant only for women who had received chemotherapy, and the higher risk of having an infant small for gestational age was significant only for women who had received chemotherapy or who had a late pregnancy (more than 2 years to 5 years after cancer diagnosis).
Among breast cancer survivors, those who became pregnant actually had lower risks of disease-free survival events (hazard ratio, 0.73; P = .016) and death (HR, 0.56; P < .001). Findings were similar in the subset of studies that adjusted for the so-called healthy mother effect.
Pregnancy did not significantly affect disease-free survival among women with hormone receptor–positive disease and appeared protective among women with hormone receptor–negative disease (HR, 0.72).
Pregnancy also appeared safe in terms of overall survival, irrespective of survivors’ BRCA status, nodal status, receipt of chemotherapy, pregnancy outcome (completed vs. abortion), and pregnancy interval.
This study was limited by the lack of patient-level data and by the fact that most of the included studies had a retrospective design, Dr. Lambertini acknowledged.