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Chemotherapy for Breast Cancer Doesn’t Seem To Increase Risk of COVID-19 Infection or Death

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A study looking at more than 3,000 women who received treatment for breast cancer in New York City during the height of the COVID-19 pandemic found that women treated with chemotherapy were no more likely to be infected with COVID-19 or die from COVID-19 than women treated with other medicines that don’t weaken the immune system.

The research was presented online on June 4, 2021, at the 2021 American Society of Clinical Oncology Annual Meeting. Read the abstract of “Risk for SARS-CoV-2 infection in patients with breast cancer treated with chemotherapy, biologic therapy or active surveillance: Patient outcomes from multicenter institution in New York.”

Chemotherapy and the immune system
About the study
What this means for you

Chemotherapy and the immune system

Chemotherapy destroys cancer cells because the medicines target rapidly dividing cells. But normal, healthy cells in your blood, mouth, intestinal tract, nose, nails, vagina, and hair also divide rapidly. So chemotherapy affects them, too.

Many chemotherapy medicines cause low white blood cell counts. Neutrophils are a type of white blood cell that is a very important part of your immune system. Neutrophils fight infection in the body. When your neutrophil counts are low — called neutropenia — you have a particularly high risk of developing an infection. Neutropenia is a side effect of many chemotherapy medicines used to treat breast cancer.

Because chemotherapy can lead to neutropenia, many experts were concerned that chemotherapy was too dangerous to use during the COVID-19 pandemic. This led to treatment delays or, in some cases, people avoiding chemotherapy.

Hormonal therapy medicines — which treat hormone-receptor-positive breast cancer — work by lowering the amount of estrogen in the body or by blocking the action of estrogen on breast cancer cells.

Therapies that target the HER2 receptors on HER2-positive breast cancer cells are called anti-HER2 medicines.

Hormonal therapy medicines and anti-HER2 medicines have minimal effects on the immune system compared with chemotherapy.

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About the study

The researchers who did this study wanted to see if chemotherapy for breast cancer was linked to a higher risk of being infected with COVID-19 or dying from COVID-19 compared with other breast cancer treatments that don’t weaken the immune system.

Researchers looked at the medical records of 3,062 women treated for breast cancer between Feb. 1 and May 1, 2020, at NYU Langone’s Perlmutter Cancer Center in New York City and Long Island.

Of the women in the study:

  • 379 were treated with chemotherapy
  • 2,343 were treated with hormonal therapy or anti-HER2 medicines
  • 340 had no treatment but were regularly monitored (called active surveillance)

During the study, 641 women were tested for COVID-19 and 64 were diagnosed with COVID-19. Overall, 2.1% of the women were diagnosed with COVID-19.

The number of women infected with COVID-19 by treatment group was as follows:

  • 18 women (4.70%) who were treated with chemotherapy were infected with COVID-19
  • 43 women (1.80%) who were treated with hormonal therapy or anti-HER2 therapy were infected with COVID-19

The researchers calculated that the risk of being infected with COVID-19 was:

  • 3.5% for women treated with chemotherapy
  • 2.7% for women treated with hormonal therapy or anti-HER2 medicines

During the follow-up period, 27 of the women died. Ten of those women died from COVID-19.

Of the women who died from COVID-19 by treatment group:

  • 4 women (1.10%) who were treated with chemotherapy died from COVID-19
  • 2 women (0.10%) who were treated with hormonal therapy or anti-HER2 medicine died from COVID-19

The researchers calculated that the risk of dying from COVID-19 was:

  • 0.7% for women treated with chemotherapy
  • 0.1% for women treated with hormonal therapy or anti-HER2 medicines

“Our results show that patients can safely receive breast cancer therapy, including chemotherapy, during the pandemic,” said study lead investigator and Perlmutter Cancer Center medical oncologist Douglas Marks, M.D., in a statement.

The researchers also looked to see if other factors affected the women’s risk of dying from COVID-19.

They found that obesity and older age were linked to a higher risk of dying from COVID-19. These results were similar to results from other studies looking at risk factors for COVID-19 mortality.

It’s important to know that the women in the study were following COVID-19 precautions.

“During visits occurring at cancer center locations, patients were required to wear masks,” Dr. Marks told “Patients were additionally encouraged by cancer center staff to wear masks in the community, as well as wash hands frequently and socially distance. We believe that the low incidence of COVID-19 infection observed in the full study cohort support the efficacy of these measures.”

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What this means for you

If you’ve been diagnosed with breast cancer and chemotherapy is part of your treatment plan, the results of this study are encouraging and strongly suggest there is no need to delay chemotherapy because of the COVID-19 pandemic.

Still, it’s important to keep several things in mind:

  • There are some anti-HER2 medicines, such as Enhertu (chemical name: fam-trastuzumab deruxtecan-nxki) and Kadcyla (chemical name: T-DM1 or ado-trastuzumab emtansine), that are combinations of an anti-HER2 medicine and a chemotherapy medicine. While considered anti-HER2 therapies, they also can weaken the immune system. It’s not clear whether this study considered these medicines chemotherapy or anti-HER2 medicines.
  • Other targeted therapy medicines called CDK4/6 inhibitors are used to treat certain types of breast cancer. Ibrance (chemical name: palbociclib), Kisqali (chemical name: ribociclib), and Verzenio (chemical name: abemaciclib) are CDK4/6 inhibitors. All the CDK4/6 inhibitors may cause severe lung problems. People with lung problems have a much higher risk of serious complications if they’re infected with COVID-19. It’s not clear if any of the women in the study were treated with CDK4/6 inhibitors.
  • The immunotherapy medicines Keytruda (chemical name: pembrolizumab) and Tecentriq (chemical name: atezolizumab) are used in combination with chemotherapy to treat certain types of PD-L1-positive breast cancer. It’s not clear if any of the women in the study were treated with Keytruda or Tecentriq.

Since the beginning of the pandemic, the Centers for Disease Control and Prevention (CDC) has issued evolving recommendations on wearing a face mask. The recommendations are based on the number of people vaccinated, as well as how contagious the current COVID-19 strains are.

On July 27, 2021, the CDC recommended that fully vaccinated people should wear masks in indoor public settings if they live in areas where COVID-19 is spreading at “substantial” or “high” levels. This CDC tool shows you whether COVID-19 is spreading at low, moderate, substantial, or high levels where you live.

All unvaccinated people should wear a mask in public indoor and outdoor settings.

The CDC is recommending these extra precautions because a newer strain of COVID-19, called the Delta variant, is more contagious than previous strains and is spreading throughout the United States. Getting sick from COVID-19 — even the Delta variant — seems to be uncommon in people who are fully vaccinated, but it can happen. Still, “breakthrough infections” in people who are fully vaccinated rarely cause severe illness or hospitalization.

The CDC says that fully vaccinated people have a lower risk of transmitting COVID-19 to people who are unvaccinated. But it’s unclear if fully vaccinated people can spread the Delta variant more easily than other strains of COVID-19.

The latest CDC recommendations also say that everyone should wear masks in schools. Additionally, the CDC says that all fully vaccinated people may want to wear a mask in public indoor settings for extra protection, especially if they have a weakened immune system or live with someone who has a weakened immune system or a higher risk of severe illness from COVID-19. If you’re immunocompromised, the CDC recommends that you talk to your doctor about taking extra precautions, even if you are fully vaccinated. If you know someone who is immunocompromised or has a medical condition that puts them at higher risk for severe complications from COVID-19, it’s a good idea to wear a mask when you visit them indoors, even if you both are fully vaccinated.

If you have been fully vaccinated for COVID-19, the CDC also recommends that you wear a mask in places where masks are required (such as businesses, hospitals, correctional facilities, homeless shelters, and when traveling on planes, buses, trains, and other types of public transportation).

Read more about Staying Well During COVID-19.

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Written by: Jamie DePolo, senior editor

Reviewed by: Brian Wojciechowski, M.D., medical adviser

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