Study Finds Many Breast Cancer Patients Who Pause Treatment When Pregnant Never Resume

A new study from Stanford Medicine suggests that only one-third of women who paused breast cancer treatment because of a pregnancy “resumed endocrine therapy after delivery, and only about two-thirds resumed regular breast imaging (which is also paused during pregnancy and breastfeeding) to detect recurrence.”

Endocrine therapy is used by people whose breast cancers need estrogen to grow, and patients are typically treated for five or more years. Ideally, the therapy is resumed as soon as possible. Julia Ransohoff, the lead author of the study, said that the study showed that recurrent breast cancer in people who don’t resume treatment (nearly 20% of the patients analyzed) is about “twice as high as we would expect.”

The study authors used a research database maintained by Stanford to “identify 215 women who were diagnosed with breast cancers from stage 0 to stage 3 between January 2000 and October 2024 and who later became pregnant. The median age at diagnosis was 33.6 years. Of these women, 161, or 75%, were eligible for hormone therapy and 130 were eligible for breast imaging (women who had both breasts removed as part of their initial treatment were ineligible).” Among the 113 of these women who began endocrine therapy, “only 36 (32%) completed five years or more. Among the 81 who paused their endocrine therapy for pregnancy (with a median duration of 21 months), 36 (32%) resumed the therapy.”

Ransohoff theorizes that the impact on quality of life to people on these drugs in addition to “all the hormone changes and stress that go along with being a new parent” may contribute to the relative lack of resumption of treatment.