Causes of Death After Breast Cancer Diagnosis Provide Insight into Patient Counsel

Though breast cancer remains the most common cause of death following a diagnosis, other non-breast cancer causes of death (predominately heart and cerebrovascular disease) represent a significant number of deaths among patients, according to a study published in Cancer.¹

These data may provide critical insight into how breast cancer survivors should be counseled regarding future health risks.

Of the cohort of 754,270 women with breast cancer in the US diagnosed during 2000 through 2015 studied using the Surveillance, Epidemiology, and End Results (SEER) program, 183,002 (24.3%) died during the follow-up period. The greatest proportion of deaths (46.2%) occurred within 1 to 5 years after diagnosis. Most of the deaths occurred from breast cancer itself or from other cancers, and the number of deaths decreased as more years passed after diagnosis.

The most common noncancer causes of death within <10 years after diagnosis were heart diseases, followed by cerebrovascular disease. However, >10 years after diagnosis, the most common noncancer causes of death were heart diseases followed by Alzheimer disease. Moreoever, patients had a statistically significant higher risk of death from chronic liver diseases within 5 to 10 years after diagnosis compared with the general population (SMR, 1.23; 95% CI, 1.09-1.38) and had statistically significant higher risks of death from Alzheimer disease (SMR, 1.21; 95% CI, 1.14-1.29) and from diseases of the heart (SMR, 1.06; 95% CI, 1.02-1.09) >10 years after diagnosis.

Other notably important noncancer causes of death included chronic liver disease, septicemia, other infectious and parasitic diseases, and suicide. Some differences in mortality risk based on risk were also reported.

“The overall survival outcomes and survival rates of patients with (breast cancer) have significantly improved in the United States throughout the last 2 decades,” the authors wrote. “Therefore, patients are living longer after a (breast cancer) diagnosis to a point at which other morbidities and mortalities significantly affect their overall survival; hence it is crucial to address deaths from non-(breast cancer) causes when counseling patients about prognosis and survivorship.”

In regard to cardiac causes of death, cardiotoxicity is a recognized adverse event of the anthracyclines and HER2-directed agents. Additionally, the risk of cardiac dysfunction generally becomes higher when trastuzumab is administered after anthracycline-based chemotherapy, but this is generally considered reversible. Radiotherapy can also play a significant role in the management of breast cancer and is known to increase the risk of myocardial infarction, especially after treatment of left breast tumors. However, in evaluating the subgroup of patients who received prior chemotherapy or radiation, there did not appear to be an increase in the risk of cardiac deaths.

Furthermore, with reference to cerebrovascular-disease related deaths, endocrine therapy using tamoxifen has previously been associated with increased incidence of thromboembolic events, with an increased risk of venous thromboembolism, pulmonary embolism, and stroke, similar to the risks associated with hormone-replacement therapy. Aromatase inhibitor adjuvant therapies have been associated with increased serum lipid levels through decreasing estrogen levels, potentially increasing cardiovascular side effects.

With respect to the notion that breast cancer survivors are generally more susceptible to developing second primary cancers, such as lung, colorectal, and endometrial cancers, lymphomas, and others, the researchers also placed increased emphasis on advising breast cancer survivors to follow proper screening and preventative measures for other cancers. 

According to the American Cancer Society, about 42,170 women will die from breast cancer in 2020 alone. Breast cancer is the second leading cause of cancer death in women, however, since 2007 the death rates in older women have continued to decrease.²

References:

1. Afifi AM, Saad AM, Al-Husseini MJ, Elmehrath AO, Northfelt DW, Sonbol MB. Causes of Death After Breast Cancer Diagnosis: A US Population-Based Analysis. Cancer. doi:10.1002/cncr.32648.

2. American Cancer Society. How Common Is Breast Cancer? American Cancer Society webpage. Published January 8, 2020. cancer.org/cancer/breast-cancer/about/how-common-is-breast-cancer.html. Accessed January 10, 2020.