One Dose of 5-FU Chemotherapy Can Kill You

One dose of 5-FU chemotherapy can kill you if you have a DPD enzyme deficiency. 

Warning: There are multiple points in this article in which your head might explode. Proceed with caution.

5-FU (5-fluorouracil) – affectionately referred to as “5 Feet Under” and “5 F.U.” and sold as Fluoroplex, Tolak, Efudex, Carac, and Adrucil – is a 50-year-old chemotherapy drug still commonly used today to treat colorectal, breast, lung, stomach, esophageal, cervical, and pancreatic cancer. The oral version of 5-FU is capecitabine, sold under the brand name Xeloda. 

Side effects of 5-FU include varying degrees of diarrhea, nausea, vomiting, low red and white blood cell counts, brain damage, and heart damage.

The American College of Cardiology published a meta-analysis in April 2019, ranking 5-FU as one of the most cardio-toxic drugs used for solid tumor cancers. It was reported that cardiovascular disease symptoms and heart attacks were observed in as little as 12 hours of intravenous infusions. Toxic reactions to 5-FU and capecitabine also include heart failure, seizures, and coma.

Fun fact: Chemotherapy drugs are highly toxic and must be detoxified by the body, or else they can become lethal.

Dihydropyrimidine Dehydrogenase (DPD) is a liver enzyme largely responsible for deactivating and detoxifying more than 80% of 5-FU from the body. But here’s the problem… Some people have reduced DPD enzyme activity, or none at all.

Without the DPD enzyme, fluorouracil-based drugs (5-FU and capecitabine) continue to poison the body indefinitely, resulting in overwhelming toxicity, collateral damage, and for some, agonizing death.

True DPD deficiency affects 5% of the population. That means 1 out of every 20 cancer patients has a significant risk of death from as little as 1 dose of 5-FU.

Another 3% to 5% of the population has a partial DPD deficiency and will also suffer severe and potentially life-threatening side effects, above and beyond the already severe side effects of 5-FU. 

In 2010, Blue Cross/Blue Shield insurance reported that 30% of cancer patients receiving 5-FU had serious side effects, including hospitalization and death.

It’s estimated that over 1,300 people die every year from 5-FU toxicity in the United States alone. Remember, this is just one chemo drug we’re talking about.

If only there was a way to test and see if a patient was deficient in the DPD enzyme before giving them 5-FU or capecitabine…

There is! It’s a blood test that costs around $100 to check for the DPD enzyme deficiency. 

But most cancer patients are not given this test, or even told about it, before they are given 5-FU. There are two plausible reasons for this. Oncologists either don’t know about the DPD enzyme deficiency risk and the test…or they don’t care.

This test may or may not be covered by insurance, depending on the policy.

There is also an antidote to 5-FU poisoning called Vistoguard (uridine triacetate).

But it must be given within 4 days, and it costs over $30,000.

Vistoguard also may or may not be covered by insurance.

Real Life 5-FU Tragedies
A June 2019 Daily Mail article criticized Britain’s National Health Services for not warning bowel (colon) cancer patients of the risks of 5-FU, and for not testing to determine whether patients had a DPD enzyme deficiency.

The article highlighted several cases, including 66-year old Lynn Stevens, who died within a month after a single IV infusion of 5-FU. 

Per her doctor’s recommendation, Lynn agreed to chemotherapy after a successful surgical removal of an early stage bowel tumor (which had not spread), to reduce her risk of recurrence (by maybe 1-2%). 

Three days after her 5-FU infusion, the side effects intensified. According to her husband Chris, Lynn had severe diarrhea, the inside of her mouth, “looked like it had been seared with red hot coals,” and she could not eat or even swallow water. Telltale signs…

However, her doctors took nearly two weeks to diagnose the fluorouracil poisoning. By then, it was too late to save her. And the antidote is not available in the UK.

Her husband of 50 years told the Daily Mail, “No one even mentioned DPD deficiency or its risks. I don’t want the cause of her death to be recorded as cancer, but extreme chemotherapy toxicity, because that is what killed her.”

I first learned of the DPD enzyme deficiency issue from the site Know the Risk of 5-FU Chemotherapy, which is run anonymously and dedicated to a woman named Kathryn, who received one round of FOLFOX (5-FU, leucovorin, and oxaliplatin) for rectal cancer and passed away within 3 weeks, despite assurances from 3 different cancer centers that the drug combination was “fairly well tolerated.”

Signs and symptoms of life-threatening 5-FU toxicity here.

Other stories of 5-FU related deaths can be found here.

It should be noted that patients have also died from 5-FU toxicity without having the DPD enzyme deficiency. Linda Andersen is one example.

This hits really close to home
5-FU was recommended for me after surgery for Stage IIIc colon cancer in 2004, which I declined. 

A few years ago, my cousin Jeff was treated with 5-FU for Stage IV colon cancer and told he could expect to live 1-2 years with treatment. He was optimistic and feeling good after surgery, but he spiraled downward rapidly after starting chemotherapy and had similar symptoms to those described above. He was also unable to keep liquids down. Jeff was gone 3 months after his diagnosis.

I don’t know if I have the DPD enzyme deficiency, but I will be testing soon to find out.

If you or someone you love is dealing with cancer, make sure you download my free patient guide 20 Questions for Your Oncologist, which will empower you with the most powerful questions to ask, in order to make an informed decision about treatment.

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