A new precision medicine approach using genetic testing before chemotherapy treatment has demonstrated significant safety improvements for gastrointestinal cancer patients, according to research from the Perelman School of Medicine at the University of Pennsylvania. The study, published in JCO Precision Oncology, shows that pre-treatment screening for genetic variants can reduce severe chemotherapy side effects by 42% while maintaining treatment effectiveness.
Genetic Variants Drive Treatment Complications
The research focused on variants in two critical genes: DPYD and UGT1A1. The DPYD gene produces an enzyme that helps the liver break down fluoropyrimidines, commonly used chemotherapy drugs in gastrointestinal cancer treatment. About 5 to 8% of people carry DPYD variants that hinder the body's ability to process these drugs, causing them to build up to harmful levels and leading to serious side effects like reduced blood cell production, mouth sores, or hand-foot syndrome.
Similarly, the UGT1A1 gene affects how the body processes irinotecan, another key chemotherapy drug for GI cancers. Variants in UGT1A1 can cause the body to process the drug too slowly, increasing the risk of severe diarrhea or low white blood cell counts.
Clinical Trial Demonstrates Safety Benefits
The study enrolled 517 GI cancer patients at three cancer care sites in the University of Pennsylvania Health System who were scheduled to begin chemotherapy treatment with fluoropyrimidine or irinotecan. A group of 288 patients received blood tests to check for DPYD and UGT1A1 variants, with results returned in about one week to enable dose adjustments.
Among 16 patients who were found to have genetic variants and received tailored dose reductions based on test results, 38% experienced severe treatment-related adverse events. In comparison, 65% of 17 patients with the genetic variants from a biobank group who received standard doses without prior testing experienced serious side effects.
The tested group also demonstrated significantly better treatment tolerability, with lower rates of treatment dosage and frequency changes (38% vs. 76%) and fewer treatment discontinuations (31% vs. 47%).
Addressing a Critical Safety Gap
"For too long, the U.S. lagged behind Europe in adopting genetic testing for chemotherapy dosing, but our study shows it's not only feasible but also critical for patient safety," said Sony Tuteja, PharmD, MS, the study's lead author and Director of Pharmacogenomics in the Penn Medicine Center for Genomic Medicine. "With up to 1,300 deaths in the U.S. each year due to side effects from one of the most common forms of chemotherapy drugs, we've worked to make testing fast and actionable, getting results in about a week to help doctors make safer treatment decisions."
Clinical Impact and Future Implementation
Nearly 290,000 Americans are diagnosed with gastrointestinal cancers each year, including colorectal cancer, the third most common cancer diagnosis in the nation. Current chemotherapy protocols use standard dosing that doesn't account for genetic differences in how patients process these drugs.
The research demonstrates that by identifying genetic variants, doctors can lower chemotherapy doses to prevent harmful side effects without compromising treatment effectiveness. The findings highlight a scalable approach to reduce complications and improve patient outcomes, with researchers suggesting broader adoption could prevent up to 1,300 deaths annually linked to chemotherapy toxicity.
The research was funded in part by grants from the Penn Center for Precision Medicine and the National Institute of Health's National Center for Advancing Translational Sciences.
