Mount Sinai Researchers Discover Treatable Cause of Severe Anemia Associated With a Cancer Therapy
Simple folic acid supplement could help some patients remain on life-saving PARP inhibitors
Researchers at the Mount Sinai Tisch Cancer Center have identified a previously underrecognized folate deficiency that may cause severe anemia in some patients receiving PARP inhibitors, a widely used class of targeted cancer therapies.
Their findings, published in the latest issue of the journal Blood Red Cells & Iron (Blood RCI) (doi.org/10.1016/j.brci.2026.100052), suggest that routine screening and treatment with folic acid could help many patients avoid blood transfusions, hospitalizations, and interruptions to their cancer treatment.
PARP inhibitors are used to treat multiple cancers, including ovarian, breast, prostate, and pancreatic cancers associated with BRCA gene mutations. While these drugs have transformed treatment options for many patients, they commonly cause anemia, a condition in which the body does not have enough healthy red blood cells to carry oxygen throughout the body. Severe anemia can cause extreme fatigue, shortness of breath, and dizziness, and may force physicians to reduce treatment doses or interrupt therapy.
Until now, many oncologists assumed anemia caused by PARP inhibitors was mainly due to a drug class effect that causes bone marrow suppression. This study suggests that a significant portion of patients instead may develop severe folate deficiency in association with PARP inhibitors, which can be diagnosed with a simple blood test and treated with an inexpensive oral vitamin (folic acid). Folic acid helps the body form healthy red blood cells. Folate is essential for producing healthy red blood cells and supporting normal cell growth throughout the body.
"Our study challenges the long-held belief that anemia from PARP inhibitors is simply an unavoidable side effect of treatment," said corresponding author Noa Rippel, MD, Chief Fellow in Hematology and Medical Oncology at the Icahn School of Medicine at Mount Sinai and incoming faculty member at the Mount Sinai Tisch Cancer Center. "We found that a significant number of patients receiving PARP inhibitor treatment developed a new and severe folate deficiency, which led to clinically significant anemia. This condition is easy to diagnose and inexpensive to treat. Identifying this deficiency early could help patients stay on their cancer therapy while avoiding unnecessary complications."
This is the first study to systematically evaluate folate deficiency in patients receiving PARP inhibitors. Previous reports had been limited to individual case studies.
The researchers reviewed the records of 512 patients with BRCA-mutated cancers treated with PARP inhibitors. They found that 3.1 percent developed folate deficiency anemia, more than six times the estimated rate seen in the general population. Nearly 30 percent of patients also developed unexplained macrocytic anemia, a condition marked by unusually large red blood cells which is commonly associated with folate deficiency, suggesting that many additional cases may have remained undiagnosed.
More than 60 percent of patients with folate deficiency anemia required blood transfusions, many were hospitalized, and twelve of sixteen (75 percent) experienced interruptions in their cancer treatment.
The encouraging finding was that folate deficiency in association with PARP inhibition was readily treated. Patients who received oral folic acid supplements recovered their folate levels and anemia, allowing them to safely resume their PARP inhibitor therapy. The researchers also found evidence suggesting that starting folic acid supplements when PARP inhibitor treatment begins may help prevent this complication.
"These findings have the potential to change how oncologists evaluate anemia in patients taking PARP inhibitors," Dr. Rippel said. "A simple blood test and an inexpensive vitamin supplement may help improve patients’ quality of life, reduce health care costs, and help patients remain on treatments that can extend survival."
As PARP inhibitors continue to be approved for more types of cancer, the researchers believe greater awareness of folate deficiency could benefit many thousands of patients annually. The investigators hope the findings will inform future clinical guidelines and encourage routine monitoring of folate levels during treatment.
Statistical support for the study was provided by the Mount Sinai Tisch Cancer Center.
About the Icahn School of Medicine at Mount Sinai
The Icahn School of Medicine at Mount Sinai is internationally renowned for its outstanding research, educational, and clinical care programs. It is the sole academic partner for the seven member hospitals* of the Mount Sinai Health System, one of the largest academic health systems in the United States, providing care to New York City’s large and diverse patient population.
The Icahn School of Medicine at Mount Sinai offers highly competitive MD, PhD, MD-PhD, and master’s degree programs, with enrollment of more than 1,200 students. It has the largest graduate medical education program in the country, with more than 2,700 clinical residents and fellows training throughout the Health System. The Graduate School of Biomedical Sciences offers 12 degree-granting programs, conducts innovative basic and translational research, and trains more than 470 postdoctoral research fellows.
Ranked 11th nationwide in National Institutes of Health (NIH) funding, the Icahn School of Medicine at Mount Sinai is among the 90th percentile of U.S. private medical schools in Sponsored Programs Direct Expenditures per Principal Investigator, according to the Association of American Medical Colleges. More than 6,900 scientists, educators, and clinicians work within and across dozens of academic departments and multidisciplinary institutes with an emphasis on translational research and therapeutics. Through Mount Sinai Innovation Partners (MSIP), the Health System facilitates the real-world application and commercialization of medical breakthroughs made at Mount Sinai.
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* Mount Sinai Health System member hospitals: The Mount Sinai Hospital; Mount Sinai Brooklyn; Mount Sinai Morningside; Mount Sinai Queens; Mount Sinai South Nassau; Mount Sinai West; and New York Eye and Ear Infirmary of Mount Sinai.
About the Mount Sinai Health System
Mount Sinai Health System is one of the largest academic medical systems in the New York metro area, with approximately 48,000 employees working across seven hospitals, more than 400 outpatient practices, more than 600 research and clinical labs, a school of nursing, and leading schools of medicine and graduate education. Mount Sinai advances health for all people, everywhere, by taking on the most complex health care challenges of our time—discovering and applying new scientific learning and knowledge; developing safer, more effective treatments; educating the next generation of medical leaders and innovators; and supporting local communities by delivering high-quality care to all who need it.
Through the integration of its hospitals, labs, and schools, Mount Sinai offers comprehensive health care from conception through geriatrics, leveraging innovative approaches such as artificial intelligence and informatics while keeping patients’ medical and emotional needs at the center of all treatment. The Health System includes more than 9,000 primary and specialty care physicians and 10 free-standing joint-venture centers throughout the five boroughs of New York City, Westchester, Long Island, and Florida. Hospitals within the System are consistently ranked by Newsweek’s® “The World’s Best Smart Hospitals,” “Best in State Hospitals,” “World’s Best Hospitals,” and “Best Specialty Hospitals” and by U.S. News & World Report's® “Best Hospitals” and “Best Children’s Hospitals.” The Mount Sinai Hospital is on the U.S. News & World Report® “Best Hospitals” Honor Roll for 2025-2026.
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