An American Cancer Society study found less dramatic but still marked differences among cancer patients — a five-year survival rate that was 10 percentage points lower for people in the poorest counties studied, compared with those on the next rung up. Such disparities vary widely according to cancer type.

"One's likelihood of dying from cancer is definitely significantly higher if you live in poverty," Brooks said.

Cancer is generally more curable when detected early, meaning those with good insurance and the means — not just money but the time and education — to develop a good doctor relationship are more likely to get that early testing.

Snow is assured the best treatment, at a hospital he wished not to disclose. "Tony Snow is paid the salary that he's paid, and he has health insurance," said Dana Perino, filling in for him at the White House. "And I'm sure he's taken care of that way."

When VIPs get terribly sick, the hope is that their illness will inspire others to take the steps necessary to protect their own health. After her husband died from colon cancer, Katie Couric had a colonoscopy live on the "Today" show, a "Katie effect" that one study found spurred colonoscopy rates by 20 percent.

Back in 1974, the year Gerald Ford became president, his wife Betty announced she had breast cancer and would undergo a mastectomy. At the time, the illness, and the operation, were rarely discussed in public. Her disclosure prompted a surge in breast-cancer screenings.

Colon cancer is highly preventable through screening and very curable when caught early, yet only a little more than half of people with health insurance get the recommended tests and only about 20 percent without health insurance do.

Giuliani called off his New York Senate run in 2000 in large part because of a diagnosis of prostate cancer. Now 62, the former mayor was treated with the implantation of radioactive "seeds" in the prostate to zap cancer cells, and he has been cancer-free since.

McCain also has been cancer-free for more than five years. The Arizona senator, 70, carries scars after three episodes of melanoma, the most aggressive form of skin cancer. Both men, like cancer survivors generally, are at an elevated risk of having it come back.

Among recent presidents:

Ronald Reagan had surgeries for colon and skin cancer and for an enlarged prostate in his second term; his daughter Maureen died from cancer in 2001.

The elder George Bush, had a basal cell cancer removed from his face when he was vice president and more than 50 years ago lost his daughter, Robin, to leukemia.

Bill Clinton had a precancerous lesion removed from his nose in 1996 and a cancerous growth taken from his back after leaving office — a time marked most dramatically by heart bypass surgery. Clinton's mother, Virginia, died of breast cancer in 1994, two years into her son's presidency.

President Bush had three small potentially cancer-causing lesions removed from his face in 2001. His wife, Laura, had a nickel-size skin cancer tumor removed from her shin last fall.

Vice President Dick Cheney, who has a history of heart problems, had skin cancer many years ago.