Younger women with a history of breast cancer are less likely to get pregnant compared to the general public, and their babies face a higher risk of certain adverse outcomes when they do, a large meta-analysis found.
Compared with the population at large, breast cancer survivors of childbearing age were 60% less likely to go on to have a pregnancy (relative risk 0.40, 95% CI 0.32-0.49, P<0.001), reported Eva Blondeaux, MD, of IRCCS Policlinico San Martino Hospital in Genoa, Italy.
Among all women with cancer, only those with cervical cancer were less likely to undergo pregnancy following treatment (RR 0.33, 95% CI 0.32-0.49, P<0.001), according to findings presented at the virtual San Antonio Breast Cancer Symposium (SABCS).
“The reduced chance of future conception among breast cancer survivors raises awareness on the importance of offering complete oncofertility counseling at diagnosis to all young women,” Blondeaux said, but she added that the overall results of the meta-analysis “provide reassuring evidence on the feasibility and safety of conceiving in women with a prior history of breast cancer.”
Current guidelines recommend fertility counseling for young cancer patients, and do not discourage pregnancy after breast cancer, Blondeaux explained.
“However, few breast cancer survivors conceive following treatment completion,” she said. “One important reason is that patients and physicians still remain concerned about fetal and maternal safety of pregnancy after breast cancer.”
The study found no difference in pregnancy outcomes (completed pregnancies, spontaneous abortions, or induced abortions) or complications from pregnancy between patients with a history of breast cancer and the general population.
But the likelihood of caesarean section was higher in breast cancer patients (odds ratio 1.14, 95% CI 1.04-1.25, P=0.007), as was the likelihood of certain risks for offspring:
- Low birth weight: OR 1.50 (95% CI 1.31-1.73, P<0.001)
- Preterm birth: OR 1.45 (95% CI 1.11-1.88, P=0.006)
- Small for gestational age: OR 1.16 (95% CI 1.01-1.33, P=0.039)
Subgroup analyses suggested these risks were driven by those who received chemotherapy.
Finally, among women with a history of breast cancer, there was no survival detriment for those who had a pregnancy versus those who did not.
SABCS session moderator Ian Krop, MD, PhD, of Dana-Farber Cancer Institute in Boston, said he “was struck” by the affect on fetal outcomes, and noted that while congenital abnormalities weren’t statistically significant, the odds of this complication was going in the wrong direction (OR 1.63, 95% CI 0.89-2.98).
“I’ve always told patients that if they get pregnant their fetal outcomes are likely to be fine, but it sounds like this needs to be further explored,” he said.
Blondeaux said that the higher risk of delivery and fetal complications calls for closer monitoring of these pregnancies, particularly in women exposed to chemotherapy.
The meta-analysis included 39 studies that involved a total of 114,573 breast cancer patients and 8,093,401 women from the general population. Both retrospective and prospective case-control and cohort studies that involved women undergoing pregnancy after breast cancer were included. Case reports, case series, and studies on pregnancy-associated breast cancer — meaning those diagnosed during or within a year of completing pregnancy — — were excluded.
Survival in young breast cancer patients was not affected by pregnancy, with both disease-free survival (HR 0.73, 95% CI 0.56-0.94, P=0.016) and overall survival (HR 0.56, 95% CI 0.46-0.67, P<0.001) favoring patients with pregnancy after breast cancer. Sensitivity analyses that included only studies that adjusted for guarantee-time bias did not change the results.
Furthermore, in subgroup analyses, pregnancy showed no detrimental effect on survival by BRCA status, nodal status, or receipt of chemotherapy. Pregnancy outcomes (completed pregnancy or abortion) or timing of pregnancy had no effect on survival as well.
The study was funded by the Italian Ministry of Health and Italian Association for Cancer Research.