Uninsured or Medicaid-patients are more likely to be diagnosed with an advanced stage cancer than those with private insurance, a new study of the American Cancer Society revealed.

Previous studies have shown a correlation between insurance status and the stage of diagnosis for particular cancers. However, the new study is the first to examine a dozen major cancer types and to do so nationally with the most current data.

The research led by Michael Halpern, M.D., Ph.D, strategic director of health services research used data from the National Cancer Database, a hospital-based registry capturing patient information from approximately 1,430 facilities. The researchers analyzed about 3.7 million patients between ages 18 and 99 who received diagnoses from 1998 to 2004.

The study found significant association between insurance and stage at diagnosis across multiple cancer sites. The widest disparities were noted in cancers that could be detected early through standard screening or assessment of symptoms, like breast cancer, lung cancer, colon cancer, and melanoma. For each type of cancer, uninsured patients were two to three times more likely to be diagnosed in Stage III or Stage IV rather than Stage I. Smaller disparities were found for non-Hodgkins lymphoma and cancers of the bladder, kidney, prostate, thyroid, uterus, ovary, and pancreas.

“Individuals without insurance are not receiving optimum care in terms of cancer screening or timely diagnosis and follow-up with health care providers,” the researchers concluded. Advanced-stage diagnosis “leads to increased morbidity, decreased quality of life, and survival and, often, increased costs.”

It is already known that many cancers respond well to treatment when discovered in their early stages, before cancer cells spread from one part of the body to other parts. Unfortunately, more advanced cancer is much harder to treat and much more likely to kill.

The study also showed blacks and to a lesser extent, Hispanics, regardless of insurance status, were more likely than whites to have advanced cancer when first diagnosed.

“The findings of this major study are critical, not only for the 47 million Americans who have no health insurance, but also for our nation. The fact is, too many cancer patients are being diagnosed too late, when treatment is harder, more expensive, and has less chance of saving lives. We must begin to remove the barriers that stand in the way of early diagnosis and timely access to medical care if we are to give all cancer patients an equal chance in the fight,” said John R. Seffrin, Ph.D., chief executive officer for the American Cancer Society quoted by the Science Daily.

Elizabeth Ward, director of surveillance research for the Cancer Society explains the way insurance status influences cancer diagnosis. Patients with insurance are much more likely to have regular screening and physical examinations.

“If you’re uninsured, you’re about half as likely to get mammography and colonoscopy as if you’re uninsured,” she said quoted by the Atlanta Journal Constitution.

The study is published today in the British journal The Lancet Oncology.