The cancer conundrum
A heart attack in your sleep at age 99 is not a bad way to go. And that's likely to be your medical fate if you've made it into ripe old age. Such is not the case for the younger crowd. Just last month we learned that cancer has become the No. 1 killer of Americans under the age of 85, an exit that most would see as decidedly less appealing. This shift in how Americans die is the result of 40 years of steadily plummeting rates of fatal heart attacks, in the face of only small declines in cancer-related deaths. There is good reason for this development.
Success in combating heart disease is three-pronged: early diagnosis, targeted treatment, and aggressive control of risk factors. Diagnosis comes easy: The heart cries out in pain when it's losing oxygen, pounds the chest when it skips a few beats, and then gives up its secrets to a spaghetti-size coronary catheter. Arterial blockages can be corrected in a flash with a bypass or a stent, lengthening life. And heart risk factors, spelled out 50 years ago by the Framingham Heart Study, have taken hold of the public mind with great results: Smoking rates have been cut in half, and our national blood pressure and cholesterol levels have fallen with the help of new and better drugs.
What has kept cancer from galloping through our population over this same time is the growing expertise in searching out the disease before it takes hold or spreads through the body. Cervical cancer would be a big killer of American women, as it is in many parts of the world, if we did not use Pap tests to screen for the disease in its earliest form. Mammograms can pick up early breast cancers even before they are seen or felt, and with a simple blood test, PSA levels can signal prostate cancer when it is well confined within the gland's capsule. Colonoscopies let doctors snip out precancerous polyps as soon as they are spotted. Together, these four cancers (cervix, breast, prostate, and colon) will make up almost half of the 1.4 million new invasive cancers expected in 2005. They have a combined five-year survival rate of 84 percent. If these same tumors were discovered by routine screens and confined locally, average survival would move up to 95 percent. Were this the norm for all tumors, cancer deaths would be dropping like a rock. But the grim story is told by the other half of the new cancers expected to hit this year, most of which are vastly more difficult to pick up early, such as cancers of the pancreas, esophagus, liver, and lung. These four have five-year survival rates of 15 percent or less.
Nasty designs. This disparity speaks to the fact that cancer is both sneaky and inexplicably virulent in many of its forms. With its nasty designs lying deep within the nucleus of the cell, it silently and gradually rewrites a patient's own genetic code. And decoding cancer's many DNA mistakes demands the kind of genomics technology that simply was not available even a few years ago. Without this technology, treatments fly blind, with a trial-and-error approach that focuses on a cancer's chief attribute of relentless growth. This often works and has saved many lives, but not reliably so, and it invariably takes a toll on healthy cells, too. The good news is that we are beginning to translate the vast and dizzying array of malfunctioning DNA tumor profiles into new and targeted therapies.