About one in eight Nigerian women with breast cancer has an inherited mutation of the BRCA1, BRCA2, PALB2, or TP53 gene.
A new analysis of the Nigerian Breast Cancer Study confirmed that these inherited mutations drive about 12% of the country’s breast cancer cases. The findings could pave the way for the first large-scale national breast cancer gene screening program, wrote Olufunmilayo I. Olopade, MD, and her colleagues. The report is in the Journal of Clinical Oncology.
“We suggest that genomic sequencing to identify women at extremely high risk of breast cancer could be a highly innovative approach to tailored risk management and life-saving interventions,” wrote Dr. Olopade, director of the Center for Clinical Cancer Genetics at the University of Chicago, and her colleagues. “Nigeria now has data to prioritize the integration of genetic testing into its cancer control plan. Women with an extremely high risk of breast cancer because of mutations in these genes can be identified inexpensively and unambiguously and offered interventions to reduce cancer risk.”
And, since about half of the sisters and daughters of affected women will carry the same mutation, such a screening program could reach far beyond every index patient identified, the investigators noted.
“If these women at very high risk can be identified either through their relatives with breast cancer or in the general population, resources can be focused particularly on their behalf. For as-yet unaffected women at high genetic risk, these resources would be intensive surveillance for early detection of breast cancer and, after childbearing is completed, the possibility of preventive salpingo-oophorectomy. Integrated population screening for cancer for all women is the goal, but focused outreach to women at extremely high risk represents an especially efficient use of resources and an attainable evidence-based global health approach.”
The Nigerian Breast Cancer Study enrolled 1,136 women with invasive breast cancer from 1998 to 2014. These were compared with 997 women without cancer, matched from the same communities. Genetic sequencing searched for mutations in both known and breast cancer genes.
Cases and controls were a mean of 47 years old; only 6% of cases reported a family history of breast cancer. Of 577 patients with information on tumor stage, 86% (497) were diagnosed at stage III (241) or IV (256).
Among the cases, 167 (14.7%) carried a mutation in a breast cancer risk gene, compared with 1.8% of controls. BRCA1 was the most common mutation, occurring in 7% of patients; these women were 23 times more likely to develop breast cancer than were those without the gene (odds ratio, 23.4). BRCA2 was the next most common, occurring in 4% of cases and conferring a nearly 11-fold increased risk (OR, 10.76). PALB2 occurred in 11 cases (1%) and no controls, and TP53 in four cases (0.4%).
Women with the BRCA1 mutation were diagnosed at a significantly younger age than were other patients (42.6 vs. 47.9 years), as were carriers of the TP53 mutation (32.8 vs. 47.6 years).
Ten other genes (ATM, BARD1, BRIP1, CHEK1, CHEK2, GEN1, NBN, RAD51C, RAD51D, and XRCC2) carried a mutation in at least one patient each. “When limited to mutations in the four high-risk genes, 11%-12% of cases in this study carried a loss-of-function variant.”
Dr. Olopade had no financial disclosures.
SOURCE: Olopade et al. J Clin Oncol. 2018 Aug 21. doi: 10.1200/JCO.2018.78.3977.