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Enigma - A Rise In Brain Tumors Sets Off Search For A Reason
Without question, a brain tumor is one of the most frightening diagnoses you can face. Not only must you confront mortality, but also the knowledge that the slide toward death may be accompanied by something equally terrifying: the loss of self as cancer takes over the organ responsible above all for who you are.
Each year, the number of people who face such a diagnosis is increasing. Since the early 1970s, the incidence of cancerous tumors that start in the brain has steadily crept upward - increasing by more than 1 percent a year, according to a National Cancer Institute (NCI) registry.
The increase has been far more dramatic in adults age 65 older. Since 1980, incidence rates for malignant tumors beginning in the brain have increased by 2.5 percent a year, according to the NCI registry. The increases become even more apparent among older people. Since 1973, malignant brain tumors increased more than 200 percent for those 75 to 79; 300 percent in the 80- to 84-year-old group, and more than 500 percent for those 85 and older.
Even to an untrained eye, the statistics are astounding. To doctors, the numbers and possible explanations for them are the subject of controversy. Not even the question of whether brain tumors really are occurring more frequently has been settled. Many attribute the increases to better diagnostic technology and an aging population. Others, however, are exploring the possibility of whether there's something in the environment playing a role.
``The final chapter is not
yet written,'' said Dr. Ed Creagan, a Mayo Clinic oncologist. ``Ongoing
studies are clearly necessary to help clarify this important question.''
Although primary malignant brain tumors account for less than 2 percent of new cancer cases, according to the American Cancer Society (ACS), they include some of the deadliest types of cancer. One common type, glioblastoma multiforme, can double its size every 10 to 11 days.
The cancer-fighting arsenal of surgery, radiation and chemotherapy has had limited success against primary malignant tumors, according to the ACS. Although treatments have improved, survival rates remain grim.
That's one reason, experts say, that dozens of studies have looked more closely at why the numbers are rising. Potential suspects that have been all but ruled out include cellular phones, electromagnetic fields and the sweetener aspartame (Nutrasweet).
''There's a lot of interest in this,'' said Dr. Philip Lowry, a Mayo Clinic physician who recently published a study of brain tumors in elderly patients at four Twin Cities hospitals. ``I think one reason is that the outcomes are generally still so poor in the face of what appear to be rapidly increasing rates.''
Artifact Of Technology?
Until recent decades, many physicians believe, brain tumors may have been misdiagnosed as dementia or stroke because medicine didn't have the capability to detect many brain tumors.
In the 1970s, however, technology began to change that. Computed tomography (CT) scans, which use X-rays to create a three-dimensional image, became widely available and a valuable tool in diagnosing brain tumors. Magnetic resonance imaging (MRI) scanning, another powerful diagnostic tool, became widely available in the 1980s.
Many experts believe that the increasing incidence is an artifact ``dug up'' by CT and MRI scans, and they point out that the increase has occurred during the years when these technologies have came into use.
``We are diagnosing cases more frequently, not because the numbers are actually increasing, but because we have in hand a safe technology to diagnose the problem,'' Mayo's Creagan said.
Hall said more people have access to MRI and CT scans and the medical care necessary to diagnose brain tumors. But he also said he believes that the aging population in the United States and around the world may play a role. Because of better health care and better health behavior, people are living longer than their predecessors, he said.
Cancer primarily affects older people, he said. It may be that many people who have brain tumors today would not have developed them had they lived years ago, because they would not have lived long enough.
``We are not predetermined to live forever,'' Hall said. ``If at age 70, you got a pretty good set of heart and lungs, you've done the right things and haven't beaten up your body, the only thing left . . . is cancer.''
Not all physicians agree that the increased incidence is simply an artifact of better technology.
Lowry, who became interested in brain tumors after several acquaintances developed them, said that although CT and MRI scans may explain the increases in the 1970s and 1980s, some physicians believe that they can't account for the continued increases shown in the 1990s.
Lowry's article, published in the July 1998 issue of Archives of Neurology, investigated brain tumor symptoms in the elderly. ``It found that while the elderly patients had different symptoms, they appeared to be diagnosed as promptly or even earlier than younger patients,'' Lowry said.
Physicians who wrote an editorial accompanying the study said Lowry's findings suggested that the increase couldn't be explained only as an artifact.
``It seems that after the 1980s, brain imaging ceases to have artifactual contributions to the increased incidence of brain cancer, '' wrote Dr. Hassan M. Fathallah-Shaykh and Donald D. McIntire, of the University of Texas Southwestern Medical Center.
``For a long time, we thought that the increases weren't meaningful, that they were the results of the improved diagnostic technology. But more recently, some are looking at this and saying there's something else happening,'' said Dr. Eric Flores, a University of Minnesota neurosurgeon. ``While there are many schools of thought, the bottom line is that it's very hard to figure out exactly what is going on.''
Studies of possible environmental agents - such as cell phones and electromagnetic fields - haven't established links between the agents and brain tumors, experts say. Other possibilities studied and dismissed include diet, viruses, brain injury, hormones, alcohol and smoking. And although there are dozens of Internet sites blaming aspartame for brain tumors and other problems, experts say it's not likely that the sweetener is responsible for the increased incidence.
Hall, of the University of Minnesota, said the incidence began increasing before aspartame was used widely. And, he noted, aspartame' s influence also would show up a distinctive way: Aspartame is consumed mostly in diet soda, which women drink more of than men. If aspartame influenced incidence rates, more women than men would have brain tumors.
Yet, Hall said, ``the
incidence is the same in both genders.' '