NEW YORK, Feb 27 (Reuters) An analysis of men with early prostate cancer treated at the Cleveland Clinic found that those treated with external beam radiation therapy had poorer overall survival than those treated with radioactive seed implants (brachytherapy) or by surgical removal of the prostate (radical prostatectomy).

''These findings indicate that the three major forms of treatment for early-stage prostate cancer are not necessarily equivalent in terms of overall survival,'' said Dr Jay Ciezki of the Cleveland Clinic in a statement.

He reported the results on Saturday in Orlando at the Prostate Cancer Symposium.

From 1996 to 2003, over 2000 men with low- or intermediate-risk prostate cancer were treated at the Cleveland Clinic and have been followed for an average of 59 months.

The overall survival rate five years after treatment was 93.8 per cent for men treated with external beam radiotherapy, compared with 95.7 per cent for men treated with brachytherapy and 97.7 per cent for those treated with surgery.

''Overall survival rates for patients treated with external beam radiation were two percent lower across the entire length of follow up,'' Ciezki said during a press briefing.

''We really are not sure why we are seeing this,'' said Dr Eric Klein of the Cleveland Clinic, who moderated the press briefing.

''There is something biologic going on here but we don't understand it yet,'' Klein added.

REUTERS BDP ND0904