Ultrasound and magnetic resonance imaging (MRI) are not sensitive nor accurate enough technologies to diagnose early cancer of the prostate.

So concludes a 15 month study of 230 prostate cancer patients at five American institutions .

Before having surgery thepatients all underwent both imaging techniques, to see if they could accurately determine the stage of the cancer . These results were compared with information obtained at the time of surgery or afterward in the laboratory.

In the study, MRI wascorrect in only three-quarters ofadvanced disease and a little over half in localized tumours. Ultrasound was the biggest disappointment . Although the most Optimistic projections placed its accuracy at 92 per cent for sensitivity, the technique was only able to accurately diagnose two-thirds ofadvance cases of disease and a little less than half of the localized tumours.

The overall batting average of ultrasound was 58 per cent and MRI, 69 per cent.

"With either method," write authors Dr. Matthew D. Rifkin, etal, "the disease in a significant number of cases was either incorrectly staged or classified as less serious than it actually was. For example, for every 100 patients with clinically operable disease. . . for whom ultrasonography indicated that the disease had extended beyond the prostate, only 63 would actually have had such extension."

They conclude: With currently available commercial equipment, neither ultrasonography nor MRI can reliably differentiate microscopical local from advance disease in patients presenting with clinically localized disease."-New England Journal of Medicine, 6 September 1990.