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Study: Insulin resistance linked to differences in breast cancer survival between Black and White women

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Contents

At a glance                  Questions for your doctor
What does this mean for me? In depth            
Clinical trials Strengths and limitations
Guidelines Resources and reference


STUDY AT A GLANCE

This study is about: 

How blood sugar and insulin levels affect the risk of death from breast cancer in Black women compared to White women.

Why is this study important?

Black women are more likely to die from breast cancer compared to White women. More Black women have a condition called insulin resistance than White women. Insulin resistance (sometimes called pre-diabetes), is when cells do not respond well to insulin. 

This study looks at whether insulin resistance may be one of the reasons that Black women are more likely to die from breast cancer.   Insulin resistance is treatable, so knowing whether it affects breast outcomes could help researchers find ways to improve survival for Black women.

What is insulin and insulin resistance?

Insulin is a hormone made by the pancreas that helps sugar in your blood get into cells where it is used for energy. Blood sugar levels rise after you eat. In response, your pancreas releases insulin into the blood. Insulin then lowers blood sugar to keep it in a normal range.

Sometimes cells become less responsive to insulin or insulin resistant. When this happens, the pancreas keeps making more insulin to try to get sugar into cells. Eventually, the pancreas cannot keep up and blood sugar rises.

What causes insulin resistance?

Insulin resistance can be due to many things.   Genetics, age and certain lifestyle factors may affect your risk for insulin resistance.

Insulin resistance risk factors include:

  • age 45 or older
  • a close relative (parent, brother or sister) with diabetes
  • ethnicity (African American, Alaska Native, American Indian, Asian American, Hispanic/Latino, Native Hawaiian, or Pacific Islander American)
  • a personal history of  gestational diabetes or stroke
  • physical inactivity
  • smoking
  • other health conditions such as high blood pressure, abnormal cholesterol levels, obesity or hormonal conditions such as  polycystic ovary syndrome (PCOS)

You cannot tell if you have insulin resistance by how you feel. A test that checks your blood sugar levels is used to diagnosis insulin resistance.

Insulin resistance and cancer

Insulin resistance is linked to increased risk for many types of cancers. However, experts do not know why insulin resistance increases cancer risk. In addition to controlling blood sugar, insulin may cause cancer cells to grow and divide. It may also cause cancer cells to ignore signals to stop growing and die. Cancer cells often have high levels of insulin receptors, which may increase risk of a cancer growing. Anyone of these or some unknown factor may be the link between insulin and cancer.

Study findings: 

This study looked at 87 Black women and 428 White women newly diagnosed with breast cancer.  They also looked at: 

  • insulin resistance
  • breast cancer prognosis

The researchers used a statistical test to see if insulin resistance may be a reason that Black women have a worse prognosis than White women. They found that:

  • Insulin resistance is linked to worse prognosis in Black women with breast cancer.

Many factors may cause differences in breast cancer survival between Black and White women.  These results suggest that insulin resistance may be one of these factors. While the data shows a link between insulin resistance and worse prognosis, it does not show whether insulin resistance causes Black women to have a worse breast cancer outcomes compared to White women. Studies to see if lowering insulin levels improves breast cancer outcomes in Black women are needed to confirm these findings.

What does this mean for me?

This study found that insulin resistance is one factor that may contribute to worse breast cancer prognosis in Black women compared to White women. Because insulin resistance can be treated with lifestyle changes or medication, it will be important to study whether lowering insulin levels will improve breast cancer survival for Black women.

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Reference

Gallagher EJ, Fei K, Feldman SM,et al., Insulin resistance contributes to racial disparities in breast cancer prognosis in US women. 2020. Breast Cancer Research. 22: 40.
 

Disclosure

FORCE receives funding from industry sponsors, including companies that manufacture cancer drugs, tests and devices. All XRAYS articles are written independently of any sponsor and are reviewed by members of our Scientific Advisory Board prior to publication to assure scientific integrity.

This article is relevant for:

Black women

This article is also relevant for:

Healthy people with average cancer risk

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IN-DEPTH REVIEW OF RESEARCH

Study background:

Black women are more likely to die from breast cancer compared to White women regardless of the of breast cancer at diagnosis. More Black women have a metabolic condition called insulin resistance than White women. This study looked at whether insulin resistance might contribute to the association between race and breast cancer outcomes. This study also looked to see if proteins on breast cancer cells that respond to insulin differed between breast cancers from Black and White women.

Researchers of this study wanted to know:

Whether insulin resistance may be one of the factors that contributes to the association between race and breast cancer prognosis. 

Populations looked at in this study:

This study looked at 515 women newly diagnosed with invasive breast cancer. Participants were recruited from ten US hospital sites in New York, New Jersey, Connecticut, Maryland and Michigan.

A total of 87 Black women and 428 White women enrolled in the study.  Clinical data recorded for participants included self-reported smoking and alcohol use, diet and physical activity, education, income and insurance.

Study design:

At the study visit, participants had height and weight recorded which was used to calculate body mass index (BMI). Blood pressure was also recorded.

Following an overnight fast (minimum of 8 hours), a blood test was used to measure blood glucose, insulin, C-peptide, total cholesterol as well as high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol and triglycerides.  Insulin resistance was calculated from fasting glucose and fasting insulin levels.

The study used the Nottingham prognostic index (NPI) to determine prognosis. The NPI is a number calculated following surgery for breast cancer. The NPI score is based on the size of the tumor, the number of positive and the grade of the tumor.

The researchers also looked at the levels of insulin receptor and insulin-like receptor in participants tumors.

The researchers used additional statistical modeling test to see if insulin resistance may be one factor that influences poor prognosis in Black women.

Study findings: 

  • Race was associated with prognosis. 
    • 28 percent of Black women (24 of 87)  had a poor NPI prognostic score
    • 15 percent of White women (63 of 428) had a poor NPI prognostic score.
  • Race was associated with insulin resistance.
    • 40 percent of Black women (35 of 87) had insulin resistance.
    • 20 percent of While women (85 of 428) had insulin resistance.
  • Statistical modeling showed that insulin resistance mediated the association between Black race and poor prognosis.
    • Insulin receptor expression was higher in breast tumors from Black women compared to White women.
    • The ratio of insulin receptor to  insulin-like growth factor receptor 1 was higher in breast tumors from Black women compared to White women and was associated with a higher NPI score.

Limitations:

Limitations of this study included the fact that the researchers were not able to determine how long patients had insulin resistance prior to their breast cancer diagnosis. The researchers also had missing data for some patients on other breast cancer risk factors such as reproductive history.

In this study, the obesity as defined by BMI was lower in participants than would be expected for the general US population. This could be due to the fact that study participants largely resided in the east coast states of New York, New Jersey, Connecticut and Maryland. In these states, self-reported obesity by BMI is between 25 and 30 percent compared to 35 and 57 percent for women in the US. Although the exact causes of this difference in obesity are not all known, they likely  reflect differences in social and economic advantage..

Importantly the authors acknowledge that insulin resistance may be one of a number of factors that contribute to the difference between breast cancer prognosis in Black women compare to White women.

Context:

Many complex factors likely contribute to the observation that Black women are more likely to die from breast cancer compared to White women.  Data suggests that Black women are more likely to be treated differently than White women following a breast cancer diagnosis. Other barriers include include access to care, screening and treatment as well as biologic and genetic differences in tumors. In addition, research supports the link between insulin resistance and risk for many types of cancer including breast cancer. This research looked at one of the many factors that may mediate disparities in breast cancer outcomes between Black and White women.

Conclusions:

This research looked at insulin resistance and showed that it may be one factor that affects why Black women are more likely to die of breast cancer than White women. This may be due to the effects of insulin on tumor insulin receptors.  It will be important to design future studies to look at whether lowering insulin levels improves breast cancer survival for Black women.

Posted 7/30/20

Expert Guidelines
Expert Guidelines

The American Cancer Society (ACS) guidelines on exercise, nutrition and weight for cancer prevention recommend the following: 

Diet and nutrition

  • Follow a healthy eating pattern, including:
    • foods that are high in nutrients in amounts that help you get to and stay at a healthy body weight.
    • a variety of vegetables, fiber-rich legumes (beans and peas), and whole fruits in a variety of colors. Consume at least 2½ to 3 cups of vegetables and 1½ to 2 cups of fruit each day, depending on your calorie requirements. 
    • whole grains rather than refined grains. At least half of the grains you eat should be whole grains. 
  • A healthy eating pattern that limits or does not include:
    • red and processed meats.
    • sugar-sweetened beverages. 
    • highly processed foods and refined grain products.
  • It is best not to drink alcohol. People who choose to drink alcohol should:
    • have no more than 1 drink per day (women) or 2 drinks per day (men).

Exercise

  • Exercise regularly.
    • Adults should get at least 150 minutes of moderate-intensity activity (equal to a brisk walk) or 75 minutes of vigorous activity (heart rate is increased, breathing is faster and you are sweating) each week, preferably spread throughout the week.
    • Physical activity has been shown to lower the risk of several types of cancer, including breast, endometrial, and colon. It also reduces the risk of other serious diseases such as diabetes and heart disease.

Weight

  • Achieve and keep a healthy weight.
    • Being overweight or obese is a risk factor for many cancers, including breast, colon, endometrial and pancreatic. You can control your weight through regular exercise and healthy eating.

Other experts, including the following, also provide guidelines for exercise, nutrition and health: 

Updated: 07/19/2022

Questions To Ask Your Doctor
Questions To Ask Your Doctor

  • What are the signs of insulin resistance?
  • Do I have risk factors that would increase my chance of developing insulin resistance?
  • Should I be tested for insulin resistance?
  • If I have insulin resistance (or become insulin resistant), how does that affect my breast cancer prognosis?
  • If I have insulin resistance, how can that be treated?

Open Clinical Trials
Open Clinical Trials

The following clinical research studies focus on addressing in cancer. 

Updated: 11/03/2022

Open Clinical Trials
Open Clinical Trials

The following are studies focused on nutrition and cancer prevention. 

Multiple cancers

Breast cancer

Colorectal cancer

Visit our Featured Research Page and Research Search and Enroll Tool to find additional studies enrolling people with, or at high risk for cancer.

Updated: 12/05/2021

Find Experts
Find Experts

You can find a registered dietician in your area using the search tool from the Academy of Nutrition and Dietetics.  

Updated: 11/13/2021

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