Patients Need to Understand Cancer Testing Limitations

NEW YORK—A man wanted to know why his chest x-ray was normal 4 months before he was diagnosed with stage IV lung cancer. A woman wanted to know how her mother could have negative tumor markers and seven brain metastases at the same time.

The meaning and limitations of medical tests may confuse and even anger patients and families. The problem came up several times during the call-in part of a Cancer Care, Inc. teleconference on lung cancer given by Ronald Blum, MD.

Dr. Blum, director of the Comprehensive Cancer Center and chief of the oncology section at St. Vincents Hospital, New York, dealt with the topic compassionately and honestly.

To the man who was diagnosed with stage IV disease and brain metastases 4 months after a normal chest x-ray, Dr. Blum explained that “the growth rates of lung cancers, of any cancer, are highly variable for reasons that we don’t understand. The problem is that the chest x-ray is a fairly insensitive technique. Even the CT scan has not been proven as a useful screening device to give us lead time to treat the disease before it spreads. So your story is certainly one that I do hear and unfortunately is characteristic of lung cancer.”

To the daughter whose mother’s blood tests failed to reveal lung cancer metas-tases to the brain, he explained that, as yet, tumor markers have not been established for most lung cancers. “Some lung cancers do give off proteins that are common to some other cancers like breast cancer, colon cancer, and glandular cancer,” he said, and these proteins, although not of proven value, are sometimes used as one of a number of methods for assessing recurrence.

“To look for recurrence and progressive disease, we use the total picture rather than a single test,” he said. “How does the patient feel? Has there been any apparent weight loss? Are there new symptoms? Are there any abnormal blood values, including tumor markers? What about the x-rays? We use all of those.”

The issue for brain metastases, he pointed out, is that the brain is isolated. “It’s protected so that it’s not in the same communication with the blood, and this can often be a silent area of recurrence. It’s not uncommon for the tumor marker to be normal,” he said.

Reasons for Low Hematocrit

Another lung cancer patient wondered whether the reason for her low hematocrit could be faulty nutrition. Probably not, Dr. Blum replied. “Wouldn’t it be nice if a little food would take care of it?” he said. “But anemia for people with cancer is multifactorial. The most common cause is the anemia of chronic disease, and it has nothing to do with nutrition.”

For reasons we don’t understand, he said, “in cancer patients, the body doesn’t make red blood cells in a normal way, and it’s not because of low iron. We think it’s probably due to decrease of the hormone erythropoietin. So if your count is low, getting a transfusion or being started on Procrit (epoetin alfa) could make an enormous difference.”