Why does cancer relapse?

The Cancer Sleeper Cell

Opinion
Siddhartha Mukherjee, assistant professor of medicine, medical oncology at Columbia University and author (The New York Times, October 29, 2010)"The word 'relapse' comes from the Latin for 'slipping backward,' or 'slipping again'…It carries a particularly chilling resonance in cancer -- for it signals the reappearance of a disease that had once disappeared. When cancer recurs, it often does so in treatment-resistant or widely spread form. For many patients, it is relapse that presages the failure of all treatment. You may fear cancer, but what cancer patients fear is relapse.

Why does cancer relapse? From one perspective, the answer has to do as much with language, or psychology, as with biology. Diabetes and heart failure, both chronic illnesses whose acuity can also wax and wane, are rarely described in terms of 'relapse.' Yet when a cancer disappears on a CT scan or becomes otherwise undetectable, we genuinely begin to believe that the disappearance is real, or even permanent, even though statistical reasoning might suggest the opposite. A resurrection implies a previous burial. Cancer’s 'relapse' thus implies a belief that the disease was once truly dead.
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Immune Discovery Opens Up New Line of Attack Against Viruses
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Ian Sample(The Guardian, London, online, November 1, 2010)
"In a report published today, scientists revealed a previously unknown way that the immune system attacks infections, a finding that offers a new approach to treating diseases caused by viruses…The body tackles infections by unleashing biological foot soldiers called antibodies that stick to viruses as they circulate in the bloodstream. For the past 100 years, scientists working on immunity generally believed this made it harder for viruses to get inside healthy cells and so spread illness around the body. But the new study has shown that for many viruses, antibodies work in a very different way. Instead of preventing viruses from infecting cells, the antibodies follow the invader inside and co-ordinate an immune attack from within.
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