ATLANTA (AP) -- A positive attitude does not improve the chances of surviving cancer and doctors who encourage patients to keep up hope may be burdening them, according to the results of research released Monday.

Optimism made no difference in the fate of most of the 179 cancer patients that Australian researchers followed over five years. Only eight people were still living by the time the study ended in 2001.

All the patients studied were suffering from a common form of lung cancer.

Although the study was small and dealt with a kind of cancer that offers little chance for survival (about 12 percent of patients live beyond five years), health experts say it is the first scientifically valid look at optimism and cancer. The results surprised researchers, who expected optimistic patients to live longer than their hopeless counterparts.

Patients are burdened by trying to maintain a positive outlook during their difficult situations, said researchers from the Peter MacCallum Cancer Centre in Melbourne, Australia, and five other health centers in an article published Monday in the journal Cancer. The study found that optimism dimmed when patients experienced the toxic effects of cancer treatment and when they learned more about the realities of the disease.

"We should question whether it is valuable to encourage optimism if it results in the patient concealing his or her distress in the misguided belief that this will afford survival benefits," the study's lead author Penelope Schofield wrote. "If a patients feels generally pessimistic ... it is important to acknowledge these feelings as valid and acceptable."

Although optimism may not help cancer patients live longer, it can help patients in other ways, according to the American Cancer Society, which publishes the journal Cancer.

A positive attitude can help lead to healthier eating habits, stopping smoking, drinking less, exercising more and learning more information about one's disease and treatment options. Cancer patients have learned to live with therapy, avoid fatigue and even have returned to work, said Dr. LaMar McGinnis, senior medical consultant for the Atlanta-based society.

"It is disappointing they don't reflect on quality of life," McGinnis said. "We did not have any illusions that optimism influences therapy but we do believe that optimism and hope does influence the quality of life a patient has."

Copyright 2004 The Associated Press. All rights reserved.