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Medicine

New cancer drugs show a cure's as elusive as ever

By Associated Press
© St. Petersburg Times
published July 27, 2003

Not long ago, the defeat of cancer seemed inevitable. Decades of research would soon pay off with a completely fresh approach, an arsenal of clever new drugs to attack the very forces that make tumors grow and spread and kill.

No more chemotherapy, the thinking went. No more horrid side effects. Just brilliantly designed drugs that stop cancer while leaving everything else untouched.

Those elegant drugs are now here. But so is cancer.

The approach, which appeared so straightforward, has proven disappointingly difficult to turn into broadly useful treatments. Some now wonder if malignancy will ever be reliably and predictably cured.

The dearth of substantial impact so far suggests the fight against cancer will continue to be a tedious slog, and victories will be scored in weeks or months of extra life, not years. The full potential of the new approach may take decades to be realized.

The drugs, called targeted therapies, are intended to arrest cancer by disrupting the internal signals that fuel its unruly growth. Unlike chemo, which attacks all dividing cells, these medicines are crafted with pinpoint accuracy to go after the genetically controlled irregularities that make cancer unique.

Several have made it through testing, but despite their apparent bull's-eye hits, lasting results are rare. Instead, these new drugs turn out to be about as effective - or as powerless - as old-line chemotherapy. Aimed at the major forms of cancer, they work spectacularly for a lucky few and modestly for some.

But for most? Not at all.

Doctors have many theories about what's gone wrong. But it is clear that cancer is a surprisingly robust foe, packed with convoluted backup systems that kick in when threatened by the new drugs.

At best, experts now expect knocking down cancer will require an elaborate mixture of targeted drugs, assembled to match the distinct biology of each person's cancer.

"It's a much more complicated problem than anyone ever appreciated," says Dr. Leonard Saltz, a colon cancer expert at Memorial Sloan-Kettering Cancer Center. "It will, unfortunately, be with us for a long time."

The job is so daunting, especially for advanced cancers propelled by potentially dozens of nefarious genetic mutations, that scientists are even rethinking the goal of cancer research.

"Society as a whole, and most of the medical profession, have it wrong, understanding we'll wake up one morning and find out cancer is cured. It won't happen. The public should give it up," says Dr. Craig Henderson, a breast cancer specialist at the University of California, San Francisco, and president of Access Oncology, a drug developer.

"What we have learned by these billions of dollars invested in cancer biology is that cancer are us," he goes on. True, cancer is different. But not different enough. "Identify what makes cancer unique and wipe it out? That won't happen. We cannot wipe out the cancer without wiping out a lot of the rest of us."

Henderson and many others have shifted their sights to something less - converting cancer into a chronic disease, like diabetes or AIDS. Treatments might slow or even stop its worst effects so people survive for years reasonably free of symptoms.

Though they hoped for more, many cancer specialists seem relieved for now to have anything new to offer at all. Even small advances are welcome in a profession where progress seems glacial.

"It is slower progress than we'd like, but that's the nature of medicine," says Dr. Donald Trump, chairman of medicine at Roswell Park Cancer Institute in Buffalo, N.Y. "A disease process as complex as cancer is unlikely to yield to blockbuster effects."

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