Genetic Testing in Ultra-Young Breast Cancer Patients: A Single Institution Analysis of Breast Cancer Patients ≤ 35 Years at Diagnosis

Abstract

Since 1999, the NCCN guidelines have outlined criteria for genetic testing among high-risk patients with breast cancer. Nonetheless, fewer than 30% of eligible patients currently undergo genetic testing in the United States. Racial disparities in genetic testing rates have been demonstrated among breast cancer patients at the population level. Meanwhile, data is conflicting regarding radiation toxicity among patients with germline mutations involving DNA repair, potentially due to low rates of testing. We hypothesized that ultra-young patients with breast cancer (<35 years) from a single high-volume academic institution would have high rates of screening and fewer disparities in receipt of genetic testing, and therefore facilitate a prospective study of radiation toxicity among mutation carriers. After IRB approval, the medical records of 532 patients ages 35 and younger at time of breast cancer diagnosis between 1990 and 2010 at a single institution were reviewed. Demographic features including race, ethnicity, language, and highest education level were captured, in addition to family history, Ashkenazi Jewish ancestry, receipt of genetic counseling and genetic testing results. Statistical analysis included chi-square and linear-by-linear association tests. The overall rate of genetic testing was 55% (290/532) in this cohort. From 1990 to 1998, the annual rate of testing was roughly stable, with a mean of 42%; then following NCCN guidelines publication in 1999, the testing rate steadily increased to 89-100% by the end of the study period (years 2009 and 2010). Of 199 patients who saw a genetic counselor, 157 (79%) received genetic testing, and an additional 133 patients were tested without seeing a genetic counselor. Fifty-four patients (19%) had germline mutations in BRCA1 (n = 29), BRCA2 (n=17) or other (CHEK2=2, PTEN=2, p53=2, RAD51C=1, ATM=1). Receipt of genetic testing was correlated with higher levels of education (p=0.00084), race (p=0.047), Ashkenazi Jewish ancestry (p=0.024), and diagnosis after implementation of NCCN testing guidelines in 1999 (p=0.0002). Family history, ethnicity, language, and whether the patient had children were not correlated with receipt of genetic testing. Rates of genetic testing among ultra-young breast cancer patients were high, particularly in response to national guidelines published in 1999, after which it took 10 years to exceed 90% testing rate in this group. Disparities exist in receipt of genetic testing related to patient race and education level, even in the specialized setting, though is likely driven by early time points in this study. Future efforts will involve exploring barriers and facilitators to genetic testing that could be employed outside the tertiary care setting, and studying radiation toxicity among mutation carriers in a large center with over 90% rate of testing in high-risk groups.