(The New York Times News Service) -- Cancer death rates have been dropping since 1991 with better screening and treatment -- but people without health insurance are apparently not benefiting from those trends, according to a new national study.

Those who lack health insurance are more likely to have treatable or curable cancers go undetected, leading to dangerous and costly late-stage diagnosis, Georgia researchers report.

"This persistent problem with inadequate access to health care does translate into worse outcomes," said Tim Byers, deputy director deputy director of the University of Colorado Cancer Center in Aurora.

"It's not surprising, but this should be a slap in the head," said Byers, who was not directly involved in the new research.

For the study, published Sunday in Lancet Oncology, scientists analyzed 3.7 million U.S. cancer cases diagnosed in those six years, probably about 75 percent of all cancers.

"For cancers that can be detected early or show symptoms early, insurance makes a huge difference, a two- to three-fold difference, in terms of early diagnosis," said Michael Halpern, primary author of the new study and a researcher with the American Cancer Society in Atlanta.

The new figures suggest that uninsured people also are more likely to die of cancer than those with private insurance, Halpern said -- but the National Cancer Database his team used didn't have enough detailed data to draw that conclusion.

In Colorado, Byers said he and his colleagues have had to aggressively fight many patients' cancers that should have been caught earlier, would have cost less to treat early, and in some cases, could have been prevented entirely.

Jeff Phelps, uninsured and a current cancer patient at University Hospital in Aurora, Colo., said he was traveling in Michigan last year when chest pain forced him into an emergency room. The diagnosis: advanced lung cancer.

Three days later, a surgeon removed the top of his right lung, Phelps said, and he stayed in the hospital for a week.

Now, Phelps said, he needs follow-up chemotherapy or radiation, but he can't apply for Medicaid in Colorado until he has drawn down his retirement savings -- about $20,000 in an IRA.

"I'm using that to pay for the Michigan bills," said Phelps, 58. He estimated his bills will total nearly $50,000.

Phelps, who is unemployed, said University Hospital is now treating him, on the assumption that Medicaid will come through, eventually.

"But I'm behind on treatment now, because I've been on hold for two months," Phelps said.

Byers called deaths from some cancers -- such as breast and colon and some lung cancers -- "largely preventable," because people are getting better diagnosis and treatment earlier.

"But people without health insurance, they forgo screening, and if they have symptoms, they tend to postpone dealing with them," Byers said.

For colon cancer, that choice can be expensive as well as deadly. To remove a pre-cancerous polyp discovered in a quick screen, Byers said, costs about $900. If that polyp develops into cancer, costs multiply 100 times, he said, "not to mention the pain and extra risk involved."

The new study also showed that cancer is diagnosed later in African-Americans and Hispanics, even when insurance status is controlled for.

Halpern said researchers don't fully understand the social and cultural factors that may lead to that pattern, but distrust of the medical system may be involved, or the sense that one is not welcome in a clinic.

Increasingly, Byers said, insurance companies are covering cancer screening.

"We're making progress scientifically, but the social disparities are widening," Byers said. "These advances are creating a wider gap by social class."

Copyright 2008 The New York Times News Service. All rights reserved.