Contralateral breast cancer risk higher for women aged 35 years or younger

Key takeaways:

• Women aged 35 years or younger had higher incidence and risk for cumulative breast cancer vs. older women.
• Risk for contralateral breast cancer at certain time frames differed based on cancer subtype.

Women aged 35 years or younger with breast cancer had a higher risk for developing contralateral breast cancer compared with women older than 35 years, according to cohort study results published in JAMA Network Open.

“As a higher proportion of younger patients was observed in the age distribution of Korean patients with breast cancer compared with those in Western countries, it is important to identify and educate patients who develop breast cancer at a young age about the risk of developing contralateral breast cancer before deciding on a treatment option,” Hakyoung Kim, MD, from the division of breast surgery, department of surgery, at the University of Ulsan College of Medicine’s Asan Medical Center and the department of surgery at Dongguk University College of Medicine at Dongguk University Ilsan Hospital, Goyang, South Korea, and colleagues wrote.

Kim and colleagues conducted a cohort study with data from 16,251 Korean women (mean age, 48.6 years) with stage 0 to III breast cancer who underwent surgery for unilateral nonmetastatic breast cancer from 1999 to 2013 at Asan Medical Center in South Korea. All women were divided into younger (n = 1,318) and older (n = 14,933) groups based on whether they were aged 35 years or younger or older than 35 years.

During a median follow-up period of 107 months, younger women with breast cancer had higher 10-year cumulative incidence (7.1% vs. 2.9%; P < .001) and a higher risk for developing contralateral breast cancer (HR = 2.1; 95% CI, 1.62-2.74) compared with older women.

In women with the hormone receptor-positive/ERBB2-negative breast cancer subtype, the risk for contralateral breast cancer increased continuously over time for both younger and older women. In women with the triple-negative breast cancer subtype, contralateral breast cancer risk increased until around year 10 before decreasing for both younger and older women. However, women with the hormone receptor-positive/ERBB2-positive subtype had contralateral breast cancer risk peak earlier, with 1.7 years since first surgery among younger women and 4.8 years among older women.

“These findings might provide valuable information for physicians and could assist in the decision-making process for patients considering contralateral prophylactic mastectomy,” the researchers wrote. “However, further research with larger sample sizes and multicenter studies are warranted to confirm and validate our results.”