Breast cancer survivors less likely to get pregnant, but babies often healthy if they do

While breast cancer survivors of childbearing age are less likely to get pregnant than the general population, most of them who do become pregnant deliver healthy babies without detrimental outcomes on their long-term survival, according to a large meta-analysis presented at the SABCS 2020 Congress.

With the availability of more effective treatments for cancer, more patients are able to survive the ordeal, pointed out study lead author Dr Matteo Lambertini from IRCCS Policlinico San Martino Hospital, University of Genova in Genova, Italy.

“Today, returning to a normal life after cancer diagnosis and treatment should be considered as a crucial ambition in cancer care,” he continued. “In patients diagnosed during their reproductive years, this includes the possibility to complete their family planning.”

However, many therapies for breast cancer come with long-term toxic effects for the patients, including adverse effects on fertility, Lambertini added. 

In a systematic review and meta-analysis of 39 studies involving 8,265,713 young women, 7,505 out of the 114,573 participants who had breast cancer eventually got pregnant after diagnosis compared with 107,068 who did not. [SABCS 2020, abstract GS3-09]

The researchers found that breast cancer survivors were 60 percent less likely than the general population to become pregnant (risk ratio [RR], 0.40, 95 percent confidence interval [CI], 0.32–0.49). However, the number could be an overestimation as the analysis did not specifically include only those women who tried to conceive, and it is possible that some of them did not try to get pregnant after completing anticancer treatment, explained Lambertini.

Compared with the general population, breast cancer survivors also saw a 45 percent significantly higher risk of having preterm labour and 14 percent greater risk of undergoing a caesarean section. Moreover, risk of giving birth to an infant with low birth weight was significantly increased by 50 percent and risk of small for gestational age by 16 percent.

“The significantly reduced chances of conceiving as compared to the general population and other cancer patients should raise further awareness on the need to improve the oncofertility counselling of young breast cancer patients wishing to complete their family planning following anticancer treatment completion,” said Lambertini.

“The increased risk of foetal and obstetrical complications calls for ensuring a closer monitoring of these pregnancies,” he urged.

Nonetheless, Lambertini pointed out that the excess risk of having an infant with low birth weight or small gestational age seemed mainly restricted to women who had previously been treated with chemotherapy.

Importantly, there was no significant increase in the risk of congenital defects (OR, 1.63, 95 percent CI, 0.89-2.98) or other complications related to pregnancy or delivery.

Furthermore, patients’ outcomes were not poorer with pregnancy after breast cancer. In fact, breast cancer survivors who subsequently got pregnant saw better overall survival (OS; hazard ratio [HR], 0.56, 95 percent CI, 0.46–0.67) and disease-free survival (DFS; HR, 0.73, 95 percent CI, 0.56–0.94) than those who did not get pregnant.

The associations with survival remained even after taking into account of “healthy mother effect,” whereby women with good prognoses were more likely to try to conceive (HR, 0.52, 95 percent CI, 0.42-0.65 for OS and HR, 0.74, 95 percent CI, 0.58-0.96 for DFS).

“[Overall, the study] provides solid evidence on the safety of pregnancy after breast cancer,” stated Lambertini. “These findings are of paramount importance to raise awareness of the need for a deeper consideration of patients' pregnancy desire as a crucial component of their survivorship care plan.”