A Hard Truth About Cancer Care
Imagine a child with leukemia. Their doctor prescribes a standard chemotherapy drug. But a simple blood test—called a pharmacogenomic test—shows this child’s body processes the drug differently. The test suggests a safer dose. It’s right there in the report.
Yet, the doctor prescribes the standard dose anyway.
This happens more often than you might think, according to a new study looking at children with cancer.
Cancer treatment is tough on a child’s body. Chemotherapy drugs can cause serious side effects, like severe infections or damage to the liver. Doctors want to make treatment as safe and effective as possible.
Pharmacogenomic (PGx) testing is a tool that helps them do that. It looks at a person’s genes to predict how they will react to certain drugs. For kids with cancer, this can mean the difference between a dose that works and one that causes harm.
But knowing about the test and actually using its advice are two different things.
The Old Way vs. The New Way
For years, doctors prescribed cancer drugs based on standard guidelines. These guidelines work for the "average" patient. But no child is exactly average. Some kids process drugs very quickly, while others process them slowly.
The new way is to use PGx testing to tailor the dose to the individual child. The idea is simple: use the genetic information to give the right drug at the right dose.
But here’s the twist: A new study found that even when doctors have this genetic information, they often stick to the old, standard way of prescribing.
Think of a drug like a key and the body’s enzymes as the lock. If the lock is broken or works differently, the key might not fit right. This can make the drug too strong or too weak.
PGx testing checks the lock. It tells the doctor if the child’s lock is standard, fast, or slow. Based on that, the doctor can adjust the key—the drug dose.
For example, a child with a "slow" lock might need a lower dose to avoid toxic buildup. A child with a "fast" lock might need a higher dose to make sure the drug works at all.
Researchers looked at data from a larger clinical trial called MARVEL-PIC. They focused on 216 children with cancer who had received PGx test results.
They checked the medical records 12 weeks after the test results were sent to the doctors. They wanted to see if the doctors followed the genetic recommendations when prescribing specific drugs.
The results were concerning.
Out of over 2,000 genetic recommendations, only 64 were for drugs that were actively being prescribed during the study period. For these 64 actionable recommendations, doctors followed the genetic advice only a small fraction of the time.
Here’s the breakdown:
- Explicitly followed: 19.8% of the time. The doctor clearly adjusted the dose based on the genetic test.
- Inadvertently followed: 50.3% of the time. The doctor prescribed the standard dose, which happened to match the genetic recommendation by chance.
- Not followed: 29.9% of the time. The doctor prescribed a dose that went against the genetic advice.
One drug, mercaptopurine, showed a higher rate of explicit adherence (87.5%). But for most other drugs, adherence was low.
The study found no link between adherence and the child’s age, cancer type, or the strength of the recommendation.
This doesn’t mean genetic testing is useless. It means we need to do a better job using the information we have.
Why Aren’t Doctors Following the Advice?
The study didn’t explore the exact reasons, but experts point to a few common barriers. Doctors are busy and may not have time to review every genetic report. The recommendations might not be integrated into the electronic health record system. Sometimes, doctors are simply unaware of the test results.
If your child has cancer, PGx testing might be an option. It can provide valuable information about how to make treatment safer. But this study shows that having the test is only the first step.
You should talk to your child’s doctor about the results. Ask how the genetic information will be used in the treatment plan. Be an advocate for your child’s care.
This study had a small number of actionable recommendations (only 64). It was also embedded within a specific trial, so the results might not apply to all pediatric cancer centers. The study only looked at a 12-week window, so longer-term adherence is unknown.
The next step is to figure out how to make it easier for doctors to use PGx results. This could involve better computer systems that automatically flag genetic recommendations. It could also involve more education for doctors about the benefits of pharmacogenomics.
Researchers are working to close this gap. The goal is to make sure every child gets the safest, most personalized treatment possible.
