Study: Childbearing after breast cancer among young survivors

IN-DEPTH REVIEW OF RESEARCH

Study background:

Breast cancer is the most common cancer among adolescent and young adult (AYA) women ages 15-39. AYA women who have undergone cancer therapy may not have completed childbearing.

Researchers of this study wanted to know:

1. whether the frequency of live births among AYA breast cancer survivors differs from the general population.
2. how the frequency of adverse birth outcomes among children born to AYA breast cancer survivors compares to the general population.
3. whether birth rate and adverse outcomes vary by tumor or cancer treatment.

Populations looked at in this study:

This study, conducted by researchers from the University of North Carolina, evaluated 4,978 women with a first primary breast cancer diagnosis between the ages of 15-39 from January 1, 2000 to December 31, 2013 as listed in the North Carolina Central Cancer Registry.

Researchers evaluated basic demographic information, diagnosis date, stage, cancer treatment and tumor information. Matched birth certificate information was used to determine race, number of births and total length of pregnancy. Births to women who were pregnant at the time of diagnosis (N=91) were excluded, but subsequent births to these women who also conceived after diagnosis were included (N=6).

For each AYA survivor, researchers randomly sampled 20 women from the general population who had a live birth but did not have a history of breast cancer. The women from the general population were matched by year of delivery and maternal age of each AYA breast cancer survivor (N=6,760 total women without prior breast cancer). The life history of AYA survivors was followed until the women reached age 46, had a live birth, died, or December 31, 2014, whichever occurred first.

Study findings:  

Live birth rates

1. AYA breast cancer survivors have a lower birth rate than age-matched women in the general population.
   • 5% of AYA survivors gave birth within 5 years of diagnosis.
   • 8% of AYA survivors gave birth within 10 years of diagnosis
   • AYA survivors gave birth approximately 57% less frequently than women in the general population in North Carolina in 2013.
   • Birth rate did not differ significantly by race.
2. Birth rate differed depending on age of diagnosis.
   • AYA survivors diagnosed at 17-29 years of age were more likely to give birth than those who were diagnosed between ages 29-35. AYA survivors diagnosed at 35-39 were the least likely to give birth.
3. AYA survivors diagnosed with regional or distal cancer were less likely to give birth than those with local or in situ cancer.
4. AYA survivors treated with chemotherapy were less likely to give birth than those with surgery only, whether or not they also had radiation.
5. AYA survivors with ER-negative breast cancer were more likely to have a live birth than AYA survivors with ER-positive breast cancer. This may reflect longer cancer treatment or delay after ER therapy among AYA survivors with ER-positive cancer.
   • AYA survivors with ER-negative cancers were 1.3 times more likely to have a live birth within 8 years after diagnosis.
   • 10 years after diagnosis, similar birth rates (10%) were seen among AYA survivors who had ER-positive and ER-negative cancer.

Birth outcomes among live births

Among the 4,978 AYA survivors, 338 had one birth post diagnosis (48 had 2 births and 8 had 3 or more births). To assess birth outcomes, these 338 AYA survivors with newborns were compared to 6,760 age-matched women from the general population who were not previously diagnosed with cancer.

1. Average maternal age at delivery was 35 years for the AYA survivors.
2. Proportions for preterm births, low-weight births, small-for-gestational-age births and C-sections were similar between AYA survivors and women in the general population.
   • Prevalence of preterm births and low-weight births was slightly elevated for women with invasive breast cancer compared to those with no breast cancer history.
   • Small-for-gestational-weight births were similar among AYA survivors and women with no cancer history.
3. AYA survivors with ER-positive breast cancer had birth outcomes similar to women with no breast cancer history.
4. AYA survivors with ER-negative breast cancer were more likely to have preterm births or low-weight births than women with no breast cancer history, even after adjusting for maternal age and race.
5. Birth outcomes did not differ significantly by endocrine therapy or chemotherapy treatments.

Limitations:

Researchers caution that the numbers of births evaluated are small, and some associations observed may have occurred by chance. They could not account for the impact of cancer recurrence on live birth frequency or birth outcomes, as their registry did not provide this information. Other features, such as socioeconomic status or health behaviors, may also confound interpretation. While researchers had information on whether AYA survivors had surgery, chemotherapy and/or radiation, they lacked information about the type of chemotherapy used or other treatment details. Researchers also noted that analysis of birth outcomes among women with particular treatments or tumor types was limited by sample size. Larger future studies are needed to confirm these findings.

Conclusions:

Among adolescent and young adult breast cancer survivors, the cumulative birth rate 10 years after diagnosis was 8%. Of the women evaluated (17-39 years of age at diagnosis), birth rates were lowest for women in their 30s, those with regional or distal cancers, and those treated with chemotherapy. Overall, adverse birth outcomes were not elevated for AYA survivors as compared to women without cancer. Women with ER-negative breast cancers did have an increased frequency of preterm and low-weight births. The importance of fertility counseling and potential fertility preserving methods prior to treatment were highlighted.

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Posted 5/10/18