A common method used to diagnose localised prostate cancer, one of the more common cancers among men, may be less effective than previously believed, researchers at Sweden's Karolinska Institutet said.
Researchers measured concentrations of prostate-specific antigen (PSA) in the blood of a group of cancer patients and monitored the development of the disease in a study that was part of the Scandinavian Prostate Cancer Group collaboration.
The team said: "The PSA value for the period after the diagnosis is insufficient as a method of distinguishing with any certainty the men who will develop a fatal cancer from those with a slower tumour growth."
Men with localised prostate cancer have in general a good chance of survival even without treatment. However, many undergo major surgery or radiotherapy, which carries the risk of impaired sexual function and incontinence.
Katja Fall of Karolinska Institutet said there was a need to "find better methods of separating the patients who will develop malignant prostate cancer from those with a more benign disease".
Previous research has indicated a link between how quickly a tumour grows and the speed with which blood levels of PSA increase in the first stages of the cancer.
Fall and her colleagues monitored 267 men from Sweden, Finland and Iceland who were diagnosed with prostate cancer between 1989 and 1999.
The PSA values measured in the first two years after diagnosis were used to describe the appearance of the early PSA curve for each patient.
At the follow-up in late 2003, 34 patients had died of prostate cancer and 18 had developed metastases.
Neither the PSA reading nor the speed with which it increased during these first two years "was able to screen out with any certainty which patients would have needed intensive treatment from amongst those who would have managed just as well without," the study said.