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Pregnancy around the time of breast cancer diagnosis does not affect survival, study finds

For women with breast cancer, pregnancy does not increase the risk of dying, new research shows.

While breast cancer is less common among younger women, those who are diagnosed in their child-bearing years may have a pregnancy around the time of their diagnosis and treatment. The number of women affected may be increasing as more women have children in their late 30s and early 40s.

Breast cancer patients are often advised to complete treatment and then wait two years before becoming pregnant. A new study – the largest study looking at this question – did not find any association between pregnancy around the time of breast cancer diagnosis, and five-year survival rates.

The study looked at 7,553 women between the ages of 20 and 45, who were diagnosed with breast cancer in Ontario from 2003 to 2014. The researchers then looked at the pregnancy histories of these women, dividing them into four groups:

No pregnancy – 5,832 women who were not pregnant from five years before their diagnosis until five years after

Pregnancy before breast cancer – 1,108 women who conceived between five years before diagnosis and one year before diagnosis

Pregnancy-associated breast cancer – 501 women who conceived between 11 months before diagnosis and 21 months after diagnosis

Pregnancy following breast cancer – 112 women who conceived between 22 months after diagnosis and five years after diagnosis

Over the course of study followup, 975 women died. There was no significant difference in mortality rates between the four pregnancy categories. When the researchers looked at women who had a pregnancy six months or more after their breast cancer diagnosis, they found no increased mortality risk.

The researchers concluded that pregnancy around the time of breast cancer did not affect survival. They noted that women who have had breast cancer and who wish to get pregnant have lowest mortality rates if they conceive six months or more after diagnosis.

The study, which was led by Dr. Steven Narod, senior scientist and director of the Familial Breast Cancer Research Unit at Women’s College Research Institute, was published online in JAMA Oncology on March 9, 2017.

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  • A publication of:
  • Women's College Hospital