ER-Negative Primary Breast Cancer Linked to Higher Risk of Second Breast Cancer

Patients with estrogen receptor (ER)-negative primary breast cancer may have a higher risk of second breast cancer, but that risk appears to be time-dependent, according to research published in Cancer.

Researchers found that, in the first 5 years after diagnosis, patients with ER-negative primary breast cancer had nearly twice the rate of second breast cancer as patients with ER‐positive primary breast cancer. After the 5-year mark, second breast cancer rates were similar between the groups. 

This study included data from 36,165 women who were diagnosed with stage I-III breast cancer during 2000-2017. At the time of primary diagnosis, most patients were 55 years of age or older (58% of ER-negative and 68% of ER-positive patients). The median follow-up was 5.7 years. 

In the first 5 years after diagnosis, the rate of second breast cancer was 16.0 per 1000 person-years among patients with ER-negative primary breast cancer and 7.8 per 1000 person-years among patients with ER-positive primary breast cancer. 

Patients with ER-negative primary breast cancer had higher rates of ipsilateral second cancers than contralateral second cancers during those first 5 years. In contrast, patients with ER-positive primary breast cancer had similar rates of ipsilateral and contralateral second cancers. 

The risk of second breast cancer was higher in patients with ER-negative primary breast cancer across all treatment groups, including for patients who underwent mastectomy and those who underwent breast-conserving surgery with or without radiation. 

After 5 years of follow-up, the rate of second breast cancers was similar between the ER-negative and ER-positive groups — 12.1 vs 9.3 per 1000 person-years. 

The reasons for these differences in the timing of second breast cancer events are not fully understood, the researchers noted.

“Endocrine therapy used in the treatment of ER‐positive disease has been shown to have a carryover effect, reducing breast cancer recurrence and mortality well after treatment cessation,” the researchers wrote. “It has also been posited that ER‐positive cancer cells may have the ability to survive in a period of dormancy followed by later reactivation.”

“Regardless of the etiology, these findings suggest that ER status may be an important factor to consider for decision-making regarding the intensity and timing of surveillance imaging in women with a personal history of invasive breast cancer,” the researchers added.

Disclosures: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.

Reference

Lowry KP, Ichikawa L, Hubbard RA, et al. Variation in second breast cancer risk after primary invasive cancer by time since primary cancer diagnosis and estrogen receptor status. Cancer. Published online February 15, 2023. doi:10.1002/cncr.34679

This article originally appeared on Cancer Therapy Advisor