City of Hope researchers confirmed that Latinas with certain inherited gene mutations that raise their risk of breast cancer are more likely to develop breast cancer that responds poorly to hormone therapy.
Findings from the multicenter study were presented by City of Hope researcher Jessica Clague DeHart, Ph.D., M.P.H., assistant research professor in the Division of Cancer Etiology, during the 2012 Annual Meeting of the American Association for Cancer Research in Chicago in April.
The researchers studied Latinas who had what are known as BRCA gene mutations — genetic alterations that significantly increase their risk of developing breast and ovarian cancers.
In a previous pilot study, they found that Latinas with BRCA mutations were more likely than their white non-Latina counterparts to have breast cancers that were negative for progesterone receptors (PR). The most recent study expanded and confirmed those findings.
PR negativity means that the cancer does not depend on the hormone progesterone to grow. Some of the most successful modern breast cancer therapies that block hormones, like tamoxifen, are far less effective against these tumors. The prognosis for these cancers is poorer, and additional treatment may be necessary.
“Since PR negativity has been associated with how a patient’s breast cancer responds to endocrine therapy, further study of this condition in Hispanic women is warranted,” said Clague DeHart, who conducted her analysis under the guidance of senior study author Jeffrey Weitzel, M.D., director of City of Hope’s Division of Clinical Cancer Genetics.
Researchers in the multicenter trial enrolled 746 Latinas, of which 610 were diagnosed with invasive breast cancer. One out of every four of the women with breast cancer had either a BRCA1 or BRCA2 mutation. Overall, about half of the breast cancer cases were PR-negative.
Analysis revealed that the rate of PR negativity among Latinas with BRCA mutations was much higher than rates reported in other studies of white non-Latinas.
The study is the largest to date of high-risk Latino families in the U.S. with complete genetic profiling, clinical data and ethnic ancestry. The team is currently collecting data on white non-Latinas for a direct comparison.
The multicenter study is being conducted by the Clinical Cancer Genetics Community Research Network, an association of 19 hospitals and institutions around the country. It is supported by grants from the American Cancer Society and the National Cancer Institute (NCI).
NCI grants: CA085771 and CA153828