Although cancer survival rates among pediatric and older adult patients continue to rise, survival rates for adolescents and young adults (AYAs), defined by the National Cancer Institute as those between the ages of 15 and 39, have remained stagnant for decades. In breast cancer especially, AYAs face a worse prognosis than older women and their 5-year survival rates are lower.
While the incidence of triple-negative tumors is known to be more common among younger women and African American women, this alone does not account for the survival disparities seen in comparison with older women. A recent study by Theresa Keegan, PhD, MS, Research Scientist at Cancer Prevention Institute of California, Fremont, has found additional biologic subtypes of breast cancer in AYAs that are directly linked to their risk of dying from the disease.1
Dr. Keegan and her colleagues analyzed data from the California Cancer Registry of over 5,300 AYAs diagnosed with breast cancer between 2005 and 2009 and studied 3-year survival rates by biologic subtype: triple-negative; hormone receptor (HR)-positive and HER2-negative; HR-positive and HER2-positive; and HR-negative and HER2-positive. The researchers also evaluated data from 53,860 women between the ages of 40 and 64 diagnosed with breast cancer.
They found that adolescents and young adults diagnosed with the triple-negative subtype (found in 19% of participants) were 2.7 times more likely to die from their disease, and those diagnosed with the HR-negative/HER2-positive subtype had a 1.6 times greater risk of dying from the disease than women with the HR-positive/HER2-negative subtype (found in 41% of participants). These subtypes also occurred in higher proportions in young adult women than in older women. In addition, AYAs were more likely to be diagnosed with stage III and IV disease and high-grade tumors than were older women.
The ASCO Post talked with Dr. Keegan about her study results and the role of socioeconomic status in breast cancer survival.
Mortality Risk Factors
What factors are involved in poorer survival rates of adolescents and young adults compared to older women with breast cancer?
A number of factors contribute to the increased risk of death in AYAs. For example, there is no routine screening for breast cancer in this age group and, as a result, young women tend to get diagnosed with a later stage of disease.
In our study, it really was a diagnosis of later-stage disease that explained the short-term survival differences. So our main prevention message is that if a young adult has any concerns about breast abnormalities, she should see her doctor immediately.
Another factor that impacts survival is that the distribution of breast cancer subtypes are different in younger women than in older women. We did a study in 2012 using a very similar data set to our current study.2 We looked at the incidence of breast cancer in younger women and how it differs in younger and older women, and we found that there were certain subtypes of breast cancer, such as triple-negative, that were more common in young women and have a poorer prognosis. We also found that young women were more likely to have later stage of disease at diagnosis and high-grade disease.
When you put all these factors together, we hypothesized that AYAs would have poorer survival, as prior studies have found.
African American Women
Please talk about some of the factors that impact poorer outcomes in young adult African American women with breast cancer.
It is well established that African American women across all ages have poorer outcomes following a breast cancer diagnosis than white women. We also found that this was the case in our study. African American women tend to be diagnosed more often with triple-negative breast cancer, which has a poorer prognosis.
However, in our study, even after factoring in the higher rates of triple-negative breast cancer, African American women still had poorer overall survival. There are a lot of theories as to why African American women may do worse, including getting diagnosed at a later stage of disease, which we also considered. What we could not look at and what could still be influencing their prognosis is what happens after their diagnosis. Are these patients adhering to treatment and getting the follow-up care they need? We haven’t been able to consider how these factors contribute to worse survival.
We also found that the patient’s socioeconomic status and type of health insurance influences outcome. Fortunately, most women, regardless of their insurance status, will get initial treatment for their cancer. But it is what happens after their first course of treatment and during surveillance that can make the difference.
For example, is their insurance covering most of the medical expenses or are there high copays for treatment? Other costs associated with follow-up care that impact women with a lower socioeconomic status include the expenses incurred traveling to the doctor’s office or medical center or for childcare.
Our study and others suggest that we need a better understanding of the factors that are contributing to a worse cancer outcome in African American women. What we know is that African American women are diagnosed with breast cancer at a much lower rate than non-Hispanic white women, but their outcomes are much worse. It’s very important to focus on why.
We also need additional research to more fully understand how the distribution of breast cancer subtypes and other factors influence long-term survival in younger women compared to older women. ■
Disclosure: Dr. Keegan reported no potential conflicts of interest.
References
1. Keegan TH, Press DJ, Tao L, et al: Impact of breast cancer subtypes on 3-year survival among adolescent and young adult women. Breast Cancer Res 15:R95, 2013.
2. Keegan TH, DeRouen MC, Press DJ, et al: Occurrence of breast cancer subtypes in adolescent and young adult women. Breast Cancer Res 14:R55, 2012.
