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FDA Warns of Increased Risk of Cancer Relapse With Long-Term Use of Azithromycin After Allogeneic Stem Cell Transplant

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Key Points

  • Cancer relapse was observed in 77 patients (32.9%) with azithromycin treatment compared to 48 patients (20.8%) with placebo.
  • A total of 95 patients died in the azithromycin-treatment group vs 66 patients in the placebo group; thus, the 2-year survival rate was 56.6% among azithromycin-treated patients compared to 70.1% in those receiving a placebo.

The U.S. Food and Drug Administration (FDA) is warning that the antibiotic azithromycin should not be given on a long-term basis to prevent the inflammatory lung condition bronchiolitis obliterans syndrome in patients with cancers of the blood or lymph nodes who undergo a donor stem cell transplant. Results of the ALLOZITHRO clinical trial found an increased rate of relapse in cancers affecting the blood and lymph nodes, including death, in these patients. The FDA is reviewing additional data and will communicate its conclusions and recommendations when the review is complete.

Long-term azithromycin treatment was being studied in patients with bronchiolitis obliterans syndrome, which is caused by inflammation and scarring in the airways of the lungs, resulting in severe shortness of breath and dry cough. Patients with cancer who undergo stem cell transplants from donors are at risk for the syndrome. The manufacturer of brand name azithromycin (Zithromax) is providing a dear health-care provider letter on this safety issue to health-care professionals who care for patients undergoing donor stem cell transplants.

Azithromycin is not approved for preventing bronchiolitis obliterans syndrome. It is an FDA-approved antibiotic used to treat many types of infections affecting the lungs, sinuses, skin, and other parts of the body. The drug has been used for more than 26 years, and it is sold under brand names and as generics in various formulations by many different drug companies.

There are no known effective antibiotic treatments for prophylaxis of bronchiolitis obliterans syndrome. Health-care professionals should not prescribe long-term azithromycin for prophylaxis of bronchiolitis obliterans syndrome to patients who undergo donor stem cell transplants because of the increased potential for cancer relapse and death. Patients who have had a stem cell transplant should not stop taking azithromycin without first consulting their health-care professional.

More on ALLOZITHRO

Researchers in France identified this increased risk of cancer relapse and death while conducting a clinical trial investigating the effectiveness of long-term azithromycin to prevent bronchiolitis obliterans syndrome in patients who undergo allogenic stem cell transplant for cancers of the blood and lymph nodes. The researchers concluded that the risks of long-term azithromycin exposure after donor stem cell transplantation may exceed the benefits. The trial could not determine why the rates of cancer relapse and death were higher with azithromycin.

The researchers stopped the ALLOZITHRO trial approximately 13 months after the study completed enrollment of 480 patients because an unexpected increase in the rate of both cancer relapses and death was observed in patients taking azithromycin. Cancer relapse was observed in 77 patients (32.9%) with azithromycin treatment compared to 48 patients (20.8%) with placebo. A total of 95 patients died in the azithromycin treatment group vs 66 patients in the placebo group; thus, the 2-year survival rate was 56.6% in azithromycin-treated patients compared to 70.1% in those receiving a placebo.

In the first few months of the trial, the death rate was about equal between those receiving azithromycin and placebo. However, an imbalance occurred subsequently and continued until the 2-year time point when the study was stopped.

To help track safety issues with medicines, the FDA urges health-care professionals and patients to report side effects involving azithromycin and other drugs to the FDA MedWatch program.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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