In a study reported in JAMA Oncology, Kristen D. Brantley, PhD, MPH, and colleagues identified the risk of a second primary breast cancer among survivors of breast cancer diagnosed at age 40 or younger, including among women with and without germline pathogenic variants.
Kristen D. Brantley, PhD, MPH
Study Details
The study used data from 1,297 women aged 40 years or younger from the prospective Young Women’s Breast Cancer Study, enrolled from three U.S. sites and one Canadian site, who were diagnosed with stage 0 to III breast cancer from August 2006 to June 2015. A total of 685 women (mean age at primary breast cancer diagnosis = 36 ± 4 years) who underwent unilateral mastectomy or lumpectomy as the primary surgery for breast cancer were included in the analysis.
Key Findings
Over a median follow-up of 10.0 years (interquartile range [IQR] = 7.4–12.1 years), a second primary breast cancer developed in 17 of 685 patients (2.5%). Among the 17 patients, 2 developed ipsilateral disease and 15, contralateral disease. The median time from primary breast cancer diagnosis to second primary breast cancer was 4.2 years (IQR = 3.3–5.6 years). The 5-year cumulative incidence of second primary breast cancer was 1.5%.
Among 577 women who underwent genetic testing, the risks of second primary breast cancer at 5 and 10 years were 5.5% and 8.9% among 33 women who carried germline pathogenic variants and 1.3% and 2.2% among 544 who were noncarriers of these variants. Among patients initially diagnosed with in situ vs invasive breast cancer, the risks of second primary breast cancer were 6.2% vs 1.2% at 5 years and 10.4% vs 2.1% at 10 years.
In multivariate analysis, the risk of second primary breast cancer was significantly higher among pathogenic variant carriers vs noncarriers (subdistribution hazard ratio [HR] = 5.27, 95% confidence interval [CI] = 1.43–19.43) and among women with primary in situ vs invasive breast cancer (subdistribution HR = 5.61, 95% CI = 1.52–20.70).
The investigators concluded: “Findings of this cohort study suggest that young [breast cancer] survivors without a germline pathogenic variant have a low risk of developing a [second primary breast cancer] in the first 10 years after diagnosis. Findings from germline genetic testing may inform treatment decision-making and follow-up care considerations in this population.”
Dr. Brantley, of the Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, is the corresponding author of the JAMA Oncology article.
Disclosure: The study was funded by Susan G. Komen and the Breast Cancer Research Foundation. For full disclosures of the study authors, visit jamanetwork.com.
