Research study results have suggested that different molecular subtypes of breast cancer appear to have different specific risk factors linked to them. While these links have been explored in older, postmenopausal women extensively, less research has been done to determine breast cancer subtype-specific risk factors in younger women.
A new breast cancer research study examined the associations between breast cancer risk factors and the risk of developing specific subtypes of breast cancer in women 56 years of age or younger. For this study, 4,322 women (890 breast cancer patients and 3,422 population-based control women) were enrolled. Molecular subtypes of breast cancer were determined by analysis of the hormone receptors present. Of the 890 breast cancer cases, 51.1% were luminal A breast cancer, 27.6% were triple negative breast cancer, 13.1% were non-luminal HER-2/neu+ breast cancer, and 8.1% were luminal B breast cancer.
Luminal A breast cancer tumors are positive for estrogen receptor (ER[+]), positive for progesterone receptor (PR[+]), and negative for human epidermal growth factor receptor (HER-2[-]). Study results indicated that the risk of developing luminal A breast cancers was linked to a history of benign breast disease and a family history of breast cancer. Additionally, not having any children and older age at first birth for those women who had children both increased the risk for luminal A breast cancer.
Luminal B breast cancer tumors are similar to luminal A breast cancer tumors in that they are ER[+] and PR[+]; however, luminal B tumors are often either HER-2[+] or HER-2[-] with a high number of actively dividing cells. Luminal B breast cancer tumors tend to be larger and of a poorer grade. Luminal B breast cancer risk was linked to increasing body size, but this was only seen in premenopausal women. Luminal B breast cancer risk was also increased by an earlier age at puberty and weakly increased by an older age at first birth.
HER-2[+] breast cancer tumors stain positive for HER-2 receptors, but do not contain estrogen or progesterone receptors (ER- and PR-). HER-2[+] breast cancers are often lymph node positive and many have p53 gene mutations. The risk for HER-2[+] breast cancer was weakly increased by an earlier age of puberty, not having children, and older age at first birth.
Triple negative breast cancer tumors test negative for estrogen, progesterone, and HER-2 receptors. Triple negative breast cancers tend to be aggressive and have poorer outcomes. Triple negative breast cancer risk was increased by little or no breast feeding, increasing body size (premenopausal women), and a family history of breast cancer (particularly among women younger than 45 years).
Overall, the results of this study help clarify the different risk factors linked to each molecular subtype of breast cancer and enhance our breast cancer awareness. By enhancing our breast cancer awareness and understanding what puts us at risk for breast cancer, we are all better prepared in our fight to prevent breast cancer. While some of these factors are beyond our control, there are others like breast feeding and body weight are factors over which we have control. Factors beyond our control can be used to help develop appropriate screening and prevention strategies.