Too few women with ovarian cancer and breast cancer are getting the recommended genetic tests that help evaluate their risk of developing other cancers – which could guide changes in their clinical care – according to a population-based study done in California and Georgia.
The discrepancy is particularly strong for women with ovarian cancer, who are “dramatically undertested,” according to researchers from the Stanford University School of Medicine who led the study.
Less than one third of women with this disease had genetic tests, contrasting with national guidelines recommending genetic testing for all women with the most common form of ovarian cancer.
The study also shows the gap between genetic testing recommendations and practice was worst among black women, those with Medicaid or no insurance, and those living in poorer areas.
The findings appeared in the study, “Genetic Testing and Results in a Population-Based Cohort of Breast Cancer and Ovarian Cancer Patients,” published in the Journal of Clinical Oncology.
“We initiated this study — the largest population-based study of multigene testing in breast and ovarian cancer patients — because we wanted to see what cancer genetic testing and results looked like in the real world,” Allison Kurian, MD, MSc, one of the study’s lead authors, and an associate professor at Stanford, said in a story written by Krista Conger.
Researchers used registries from the Surveillance, Epidemiology and End Results Program to look at a large number of women diagnosed with breast cancer (77,085) and ovarian cancer (6,001), in Georgia and California, between 2013 and 2014.
They analyzed how many of these women were tested for cancer susceptibility genes between 2012 and 2016, and examined what were their results.
Tests could span mutations in BRCA1 and BRCA2 only — well-known to increase risk of breast and ovarian cancer — or also screen for variations in other genes (multi-gene panel).
The results revealed that only 24.1% of patients with breast cancer and 30.9% of those with ovarian cancer had a genetic screen.
Researchers said this rate is “inadequate,” particularly for women with ovarian cancer. Guidelines have recommended testing for all patients with high-grade serous ovarian cancer, which is the most common type of ovarian cancer, for more than 10 years.
“[A]ppropriate testing of patients with metastatic breast and/or ovarian cancer is increasingly critical both for them and to inform their at-risk relatives,” the team said.
The testing results can guide changes in patient care, according to the researchers.
Three PARP inhibitors have been approved for BRCA1/2-associated ovarian cancer: Lynparza (olaparib), Zejula (niraparib) and Rubraca (rucaparib). In cancer treatment, blocking PARP may help keep cancer cells from repairing their damaged DNA, causing them to die.
Patients with earlier-stage ovarian cancer, who have the best prognosis, were the ones with the lowest rates of testing — a shortfall that may take from patients the opportunity for risk-adapted screening for second cancers, such as breast, colon, and melanoma, associated with high-risk variants.
Among women tested for all genes advised by guidelines, 14.5% of those with ovarian cancer, and 7.8% with breast cancer, carried a mutation that warranted a potential change in their care, or that of their family members. For example, these patients and their relatives could have had the opportunity to have secondary breast cancer screening, including MRI, an earlier colonoscopy, or risk-reducing surgery.
Researchers also observed disparities in testing rates depending on ethnicity, health insurance, or socioeconomic level. Nearly one third (33.8%) of non-Hispanic white women were tested, compared with 21.6% of black women and 24.9% percent of Hispanics.
Uninsured patients tested 20.8% and those with Medicaid tested 20.3% — lower percentages as compared with the 33.9% of women with other forms of health insurance who tested.
Testing prevalence decreased to about 20.1% in poorer areas, as compared with 37.8% in residential areas with lower poverty.
Cancer-associated mutations also varied according along ethnicities. Specifically, ethnic minorities — African-American, Asian, and Hispanic patients — were more rich in variants of uncertain significance, the study found. Those are variants of unknown influence over cancer risk, typically not taken into account for healthcare decisions.
“These differences underscore the need to improve the clarity of genetic test results, especially for racial or ethnic minority patients,” Kurian said.
Genetic testing is crucial to determining the prevalence of inherited risk to cancer within a population, which informs health policies and resource planning, and is used to develop future guidelines, the researchers said.
Patients’ and clinicians’ attitudes about the value of genetic testing, and its incorporation into current cancer management practices, is challenging and limits its expanded use.
To overcome these barriers “more research is needed to identify optimal approaches to genetic testing delivery and results management” and evaluate the impact genetic testing has for patients and their families, the researchers concluded.