NEW YORK (Reuters Health) Jan 10 - The association between reproductive factors and breast cancer risk differ in women with BRCA1 vs BRCA2 mutations, researchers from China report.
Their conclusions are drawn from a systematic review and meta-analysis of 10 studies including 10,807 cases of breast cancer and 10,591 controls, all of whom carried mutations in BRCA1 or BRCA2.
There was no significant association between parity and breast cancer risk among either BRCA1 or BRCA2 mutation carriers, according to Dr. Xiaoan Liu from The First Affiliated Hospital with Nanjing Medical University, Nanjing, China and colleagues.
In contrast, older age at first birth, breastfeeding for at least 1-2 years, and older age at menarche were associated with a significantly lower breast cancer risk among women with BRCA1 mutations, the authors wrote in a paper online December 12th in Cancer Epidemiology.
Age at first birth, breastfeeding, and age at menarche did not influence the risk of breast cancer among BRCA2 mutation carriers.
"The results suggest a differential risk of breast cancer among BRCA1 or BRCA2 mutation carriers associated with reproductive factors," the researchers conclude. "The differential risk seen in BRCA1 and BRCA2 mutation carriers associated with reproductive factors suggests that responses to hormonal influences may be distinct between them."
"Future studies are needed to explore the mechanisms by which the effects of these reproductive factors on breast cancer risk differ between BRCA1 and BRCA2 mutation carriers, providing information about what can be done to reduce breast cancer risk," they add.
Dr. Liu and coauthor Dr. Wenbin Zhou did not respond to a request for comments.
In email to Reuters Health, Dr. Leena Hilakivi-Clarke from Georgetown University, Washington, DC pointed out, "Determining whether reproductive factors modify the risk of breast cancer in women who have a high risk of getting breast cancer due to a germline mutation in 'powerful' tumor suppressor genes is of importance, because they can impact a woman's decisions whether and when to have mastectomy and salpingo-oophorectomy,"
"Findings indicate that late pregnancy protects against breast cancer, compared to early pregnancy, which is totally opposite to the effect of pregnancy on sporadic breast cancer," Dr. Hilakivi-Clarke explained.
"It is not really discussed why this is," she continued. "One possibility is that early first pregnancy increases the risk significantly, compared with protective effects seen in non-mutation carriers, and therefore the increase in risk within mutation carriers is seen in women older than 30 who still might have higher risk than nulliparous women but not as high as mutation carriers who have a child at a young age."
"Results could be interpreted to suggest that BRCA1 mutation carriers should wait until they are 30 to have their first child and then nurse for a long time, perhaps up to two years," Dr. Hilakivi-Clarke said. "BRCA2 mutation carriers do not need to worry that reproductive factors modify their risk of developing breast cancer."
But Dr. Claudine Isaacs from Georgetown University told Reuters Health by email that she would be "very careful" about using these results to counsel BRCA1 and BRCA2 carriers. "These findings were based on meta-analyses from retrospective studies and while interesting are not of sufficient power for us to make management recommendations," she said.
"I agree with Dr. Hilakivi-Clarke that it is somewhat surprising that reproductive risk factors do not impact BRCA2 carriers, who tend to develop tumors more similar to those seen in women with sporadic disease (and are more often ER+)," Dr. Isaacs said.
"We are learning more about how established reproductive risk factors relate to various molecular subtypes of breast cancer (in this case, the tumors that BRCA1 and 2 carriers tend to develop)," Dr. Rebecca Troisi from the National Cancer Institute in Bethesda, Maryland told Reuters Health.
"BRCA1/2 carriers are unlikely to change their reproductive behaviors based on these results, but the findings may provide some insight into the biological mechanisms of tumorigenesis related to these particular molecular subtypes," Dr. Troisi said.
SOURCE: http://bit.ly/1ktIwc0
Cancer Epidemiol 2013.
Δεν υπάρχουν σχόλια:
Δημοσίευση σχολίου