Study: Pregnancy around the time of a breast cancer diagnosis does not negatively affect survival

IN-DEPTH REVIEW OF RESEARCH

Study background:

The number of women who become pregnant around the time of or after a breast cancer diagnosis is increasing. When treating women with breast cancer, doctors must consider the best approach for treatment as well as the health of both the mother and baby. Pregnant women do not typically receive chemotherapy during the first trimester, and radiotherapy and hormonal therapies are not recommended during pregnancy.

Previous research showed that women who were diagnosed with breast cancer during pregnancy or one year after pregnancy tend to have higher-grade breast cancers, but whether the survival rates of these women are affected is unknown. Additionally, it is not known how long women should wait after breast cancer treatment to try to conceive—some health care providers advise waiting at least 2 years because of a concern that hormones such as estrogen that are released during pregnancy may worsen survival.

Javaid Iqbal and colleagues from the University of Toronto and other institutes published their study results in JAMA Oncology in May 2017, comparing overall survival of breast cancer patients who were pregnant before, during, or after diagnosis. 

Researchers of this study wanted to know:

Does pregnancy affect survival in women with breast cancer?

Population(s) looked at in the study:

The 7,553 women involved in this study were from Ontario, Canada and had a diagnosis of breast cancer in the Ontario Cancer Registry. Only women with invasive cancer were studied (women who were younger than 20 or older than 45 at the time of diagnosis, women with a personal history of a previous cancer, and women with stage 0 breast cancer (DCIS) were excluded.)

• No pregnancy: These women did not conceive from 5 years before to 5 years after their diagnosis. At the beginning of the study, this group included 5,832 women.
• Pregnancy before breast cancer: Baby was conceived 1 to 5 years before diagnosis. At the beginning of the study, this group included 1,108 women.
• Pregnancy-associated breast cancer: Baby was conceived between the 11 months before a breast cancer diagnosis to 21 months after diagnosis. At the beginning of the study, this group included 501 women.
• Pregnancy following breast cancer: Baby was conceived 22 to 60 months after diagnosis. At the beginning of the study, this group included 112 women.

Study findings: 

1. The 5-year survival rates for breast cancer patients were:
   • About 88% for those who did not become pregnant.
   • About 85% for those who were pregnant before diagnosis (baby was conceived 1 to 5 years before diagnosis).
   • About 82% for those who were pregnant at the time of their diagnosis (baby was conceived between the 11 months before diagnosis to 21 months after diagnosis).
   • About 97%, the lowest risk of death found, for women who were pregnant 6 months or more after their diagnosis.
2. For women with pregnancy-associated breast cancer, younger women (under 35 years old) tended to have poorer overall survival.
3. Women with pregnancy-associated breast cancers were more likely to have ER-negative tumors compared to non-pregnant women (about 37% compared to about 23%).

Limitations:

The Ontario Cancer Registry does not provide some of the data that the researchers collected (tumor size, ER/PR status, etc.) for breast cancer cases that were diagnosed before 2010. Additionally, the researchers had to estimate the time of conception for women who had abortions because their data was unavailable. Finally, the researchers were unable to obtain any information on the use of hormonal treatment.

Conclusions:

This study suggests that pregnancy before, during or after a breast cancer diagnosis does not negatively affect survival, confirming other study results showing that other factors, such as age at diagnosis can impact survival for women who become pregnant around the time of a breast cancer diagnosis. More work should be done to understand the relationship between breast cancer and pregnancy. Meanwhile, this study is hopeful for women who want to have children following a diagnosis of breast cancer as well as women who were pregnant prior to, or at the time of, a breast cancer diagnosis.

Posted 5/23/17

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