Factors associated with disparities in breast cancer survival studied

By Dr. Ananya Mandal, MDOct 16 2017

According to a latest study, several factors are responsible for the differences in the survival statistics of the non-elderly women with breast cancer. For example in 2012, the health reports had revealed that black women have a 43% higher risk of death when affected with breast cancer compared to their white counterparts.

Researchers from investigators from the American Cancer Society, Emory University, and Dana-Farber Cancer Institute tried to assess if the modifiable risk factors that if changed, would bring the death risks from breast cancer at par. The study entitled, “Factors That Contributed to Black-White Disparities in Survival Among Nonelderly Women with Breast Cancer Between 2004 and 2013” appeared in the Journal of Clinical Oncology.

For this study the researchers looked at some of the modifiable risk factors that predict the risk of death due to breast cancer;

• Stage of the tumor
• Size of the tumor
• Treatment given to the patient including surgery, radiation therapy, chemotherapy and hormonal therapy
• Treatment interaction with staging
• Insurance coverage of the patient

Some of the non-modifiable risk factors for death due to breast cancer include –

• Hormone receptor status i.e. whether the tumor is Estrogen Receptor or ER positive or hormone receptor negative etc.
• Histology or cellular pathology of the tumor
• Grade of the tumor that predicts its aggressiveness
• Presence of other diseases and ailments

The team of researchers looked at 573,387 black and white women aged between 18 and 64 years with invasive breast cancer diagnosed during 2004−2012. They were followed through 2013 from the National Cancer Data Base. Relative risk of dying of the cancer was noted in all women. Initially only age was adjusted. Thereafter complex statistics were applied to see which of the modifiable and non-modifiable factors affected the outcome of the cancers in these women.

The Hazard Ratio of deaths due to breast cancer among black women when age was adjusted for was 2.09. Once other factors were also considered, the hazard ratio for black women was 1.31. A hazard ratio of 1 would mean that both white and black women had an equal mortality risk with the disease. The results from each of the two modifiable and non-modifiable risk factors showed that the contribution of the modifiable risk factors was as large as the non-modifiable risk factors. This means if these modifiable risk factors were addressed, they could reduce the differences in the mortality risk with breast cancer among whites and blacks.

There are several other differences among black and white women with breast cancer find the study. Notable among this is the difference in insurance covers. The authors write that with the advances in the treatment options for breast cancer the gap between black and white women and their death risk has narrowed. However whites seem to have benefitted more from the health care facilities available than blacks they write.

They found that compared to white women, black women were more commonly uninsured or have Medicaid. For example only 8.4 percent of the black women received Medicaid coverage or insurance compared to 22.7 percent whites. Black women also had larger tumors, which were more aggressive (higher grade) and hormone receptor negative. Hormone receptor negative cancers are usually more resistant to treatment. Even those black women with hormone receptor positive status had twice as much as risk than white women of dying due to the cancer.

The risk difference was seen to reduce when age of the patients, their area of residence, insurance, other diseases, tumor character and previous treatment was adjusted. Insurance difference alone accounted for a 37 percent increased risk of black women compared to white women.

Tumor character accounted for a 23.2 percent difference and other coexisting diseases account for 11.3 percent differences in deaths. Among women with hormone receptor-negative tumors, black women had a 49.5 percent raised risk of death compared to white women.

When other factors are considered however, the risk difference reduced. Insurance alone was responsible for a 34.1 percent excess risk. According to the authors, differences in insurance can explain around one third of the excess risk of dying due to breast cancer among the non-elderly black female population compared with white females when both are diagnosed with early stage breast cancer. Differences in the tumor characteristics account for one fifth of the difference in death risk they write.

They write in their concluding statement, “Health policy makers should ensure that the benefits of important scientific advances in prevention, early detection, and treatment of breast cancer are made available to all women, especially black women, who experience an undue share of the mortality burden from this disease….Equalization of access to care in nonelderly black women could substantially reduce ethnic/racial disparities in overall mortality of women diagnosed with breast cancer.”

Reference: http://ascopubs.org/doi/abs/10.1200/JCO.2016.34.15_suppl.6548