Cancer vaccines promising, but nothing like flu shots

Q&A

December 24, 2004|By Judy Foreman | Judy Foreman,Special to the Sun

I've heard that there are cancer vaccines. If I get one, will it prevent cancer?

Although many cancer vaccines are now being studied, so far, none has been approved by the Food and Drug Administration, said Jeffrey Schlom, chief of the Laboratory of Tumor Immunology and Biology at the National Cancer Institute.

And when they are approved, they will be aimed not at preventing disease, like the flu and polio vaccines, but to keep cancer from coming back after treatment.

Cancer vaccines are "therapeutic," meaning that they're designed to rev up the immune system to fight a cancer that's already present, or to keep the immune system primed to notice and fight any cancer cells that recur.

There are vaccines to prevent some viral infections that can lead to cancer, including an approved vaccine against hepatitis B and an experimental vaccine against hepatitis C. Both viruses are associated with liver cancer. And there is a promising vaccine against HPV, human papilloma virus, which is associated with cervical cancer.

For the cancers not associated with viruses, researchers are designing vaccines designed to directly attack proteins called antigens on the surface of cancer cells. Sometimes, the same antigens pop up in diverse malignancies -- breast cancer, lung cancer and colorectal cancer, which means that the same vaccine could be used against all these.

In other cases, cancer cells carry a unique antigen, which means a vaccine would have to be developed just against that cancer. In still other cases, researchers are working on individualized vaccines that would attack antigens unique not just to the cancer, but to the particular person.

Among the more promising vaccines are those to fight melanoma, the deadly skin cancer, said Dr. Stephen Hodi, clinical director of the melanoma program at Boston's Dana-Farber Cancer Institute.

There are dozens of such melanoma vaccines now in clinical trials, though one vaccine has been approved in Canada. As the therapeutic vaccines become approved and widely used, researchers believe it will be important to give them soon after a patient's initial treatment with surgery, radiation or chemotherapy is over -- before the cancer has time to come back in force.

I've heard you can get liver failure from taking Tylenol and drinking. How much Tylenol and how much alcohol does it take?

There's no clear answer because no one really knows "what constitutes the minimum threshold for alcohol consumption" in people who take Tylenol, said Dr. Ray Chung, medical director of liver transplantation at Massachusetts General Hospital.

A small woman, for instance, could be at risk of liver damage if she regularly consumes as few as two to three drinks a day, plus 4 grams of Tylenol (acetaminophen). That amounts to 8 Extra Strength pills of 500 milligrams each, said Dr. Rudrajit Rai, medical director of liver transplantation at Johns Hopkins Medicine.

It's not hard to reach these levels if you're in constant pain and often have a couple of glasses of wine with dinner. It's also not hard, given that acetaminophen comes in many medications besides Tylenol, including cold and sinus remedies. A healthy man can get probably away with a little more alcohol and the same dose of Tylenol.

Combining alcohol and acetaminophen is dangerous because of basic liver biochemistry. Suffice it to say that while acetaminophen is normally metabolized safely in the liver, chronic alcohol use induces an enzyme that breaks down acetaminophen into more toxic metabolites.

The label on Tylenol bottles may be overly reassuring. It says, "If you consume 3 or more alcoholic drinks every day, ask your doctor whether you should take acetaminophen or other pain relievers / fever reducers. Acetaminophen may cause liver damage."

"This may leave readers with the sense that they can get away with three drinks a day or less" and still take Tylenol safely, which may not be true, said Mass General's Chung.

At high doses, acetaminophen by itself -- 24 extra strength (500 mg) pills or more within 24 hours -- can cause acute liver failure, which can be fatal. A drug called Mucomyst can reverse liver damage if taken soon enough.

Bottom line? According to Chung, if you need to take the recommended dose of Tylenol and don't have chronic liver disease, try to stick to one drink a day or less.

Do you have a medical question? You can submit questions by e-mail to foreman@baltsun.com.

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