Putting endocrine therapy on hold to have a baby doesn’t increase risk of breast cancer recurrence or birth complications.
Women who put their endocrine treatment on hold to have children do not have a higher risk of breast cancer recurrence, according to new research presented at the San Antonio Breast Cancer Symposium this month.
The analysis of 500 women who had estrogen receptor-positive breast cancer also found that among women who temporarily stopped their endocrine treatment to become pregnant, 8.9% had their breast cancer recur in three years compared to 9.2% among women who did not stop treatment.
“They have very good survival, in fact slightly better breast cancer recurrence rates. So we know that we don’t appear to be doing them any harm, at least in the short term of up to three or four years, which is terrific,” Professor Christobel Saunders AO, breast cancer surgeon and researcher, told Oncology Republic.
Professor Saunders said the women in the study did not have higher rates of pregnancy complications and the 365 babies born during the study were not more likely to have birth defects. “Birth defects were very low and not associated with treatment,” she said.
Rates of conception and birth were even slightly higher than in the general population, said the James Stewart Chair of Surgery at Royal Melbourne Hospital and lead investigator of the West Australian arm of the POSITIVE trial.
Professor Saunders said the findings held across different groups with varying stages of cancer, grade of cancer and lymph node status.
“There wasn’t any real signal to show that any tumour subtype or patient subtype had any difference in terms of recurrence rates over and above what would be expected. That was a very good result for us.”
Most of the women who participated were under 40 and 75% had not had children before. Most of the women had stage I or II disease. During their breast cancer treatment they had endocrine therapy for at least 18 months before the trial and 62% also had chemotherapy.
Tamoxifen alone was the most prescribed endocrine treatment, followed by tamoxifen+ovarian function suppression.
The women then paused their endocrine treatment, including a three-month “wash-out period” before trying to conceive either naturally or through IVF.
Professor Saunders said the participants were also given counselling about healthy fertility and offered fertility appointments.
“If by a year they clearly weren’t going to get pregnant, then we encouraged them to restart their endocrine therapy.
“For those who got pregnant, it was a bit longer than that before they restarted their endocrine therapy because they’d have their babies and 62% of them breastfed so it could be two years before they restarted their endocrine therapy.”
Overall, there were 507 pregnancies with 365 births, and some women had more than one child, she said.
Since finishing the trial, 76% of women have resumed endocrine treatment.
Professor Saunders said for young women with breast cancer, fertility was a very important issue, often second only to survival. She said as women increasingly delayed their first pregnancies, there was a growing proportion of young women who developed breast cancer before having children.
“There’s always been concern that if you stopped your treatment that might increase recurrence, or indeed having a pregnancy with all the hormones that flow around that that might increase recurrence, but it doesn’t appear to be so, which is very good news for women.”