Breast cancer is the most common cancer worldwide. In 2021, an estimated 281,550 new cases of invasive breast cancer and 49,290 new cases of non-invasive (in situ) breast cancer are expected to be diagnosed in women in the US alone. A study published in Oncotarget found that although the risk of breast cancer was higher among women with fibroids, these women were less likely to die from the disease.
Researchers in Taiwan used the National Health Insurance Research Database of Taiwan to examine how frequent breast cancer occurred among Asian patients and how often they died from the disease. The study compared 22,001 women with newly diagnosed fibroids to 85,356 women without fibroids.
In comparison to women without fibroids, data showed the incidence of breast cancer was 35% higher among women with fibroids. By the end of the study, researchers observed that women with fibroids, although at a higher risk of breast cancer, were significantly less likely to die from the disease versus women who were fibroid-free.
One possible explanation is that the complicated balance of sexual hormone and hormone receptor status plays a critical role in the development of both breast cancer and uterine fibroids. Another possible explanation, the researchers write, is that the stage of breast cancer at diagnosis was earlier in patients with uterine fibroids than those fibroid-free.
Looking at both groups, researchers also examined risk factors for breast cancer. For example, women with fibroids who were 45 years of age and older and those who didn’t use estrogen and progesterone medications were at an increased risk of breast cancer when compared to women without fibroids. Furthermore, researchers found that having other conditions like high blood pressure, high cholesterol, diabetes, noncancerous breast tumors, menopausal and postmenopausal disorders, and infertility put women with fibroids at a higher breast cancer risk.
As the research for fibroids and breast cancer continues, this study furthers our understanding of how these diseases may be connected.
Shen T et al. 2017. “Patients with Uterine Leiomyoma Exhibit a High Incidence but Low Mortality Rate for Breast Cancer.” Oncotarget8, no. 20 (May 16): 33014–33023. PMID: 28380432.