Thymosin beta-15 predicts for distant failure in patients with clinically localized prostate cancer - Results from a pilot study

Objectives. To report the results of a pilot study on the prognostic value of a newly identified actin-binding protein, thymosin beta-15 (T beta 15), in predicting prostate-specific Antigen (PSA) and bone failure in patients with Gleason 6/10 clinically localized prostate cancer. Methods. Thirty-two patients (median age 70 years) with clinically localize d, moderately differentiated [Gleason 6/10) prostate cancer treated by exte rnal beam radiotherapy alone (68.4 Gy) with available paraffin blocks at th e Massachusetts General Hospital were evaluated for this pilot study. All p atients had clinical Stage MO disease at initial presentation, which was do cumented by bone scan (T1c-4,NX). Their corresponding biopsy specimens were stained immunohistochemically for T beta 15, which was then correlated wit h the clinical outcome in a blinded manner. The median follow-up was 6 year s (range 1 to 19) for all of the patients. Results. The outcomes of the 32 patients can be grouped into three categori es: patients with no evidence of disease (n = 11), patients with PSA failur e without documented bone failure (n = 1 I), and patients with PSA failure and documented bone failure (n = 10]. T beta 15 staining intensity strongly correlated with clinical outcome. Of those patients whose specimens staine d 3+ (strongest staining), 62% developed bone failure compared with 13% of those patients whose specimens stained 1+ (weakest staining) (P = 0.01). Th e 5-year freedom from PSA failure was only 25% for those patients with 3+ s taining compared with 83% for those with 1+ staining (P = 0.02). Conclusions. The results of this pilot study have demonstrated that T beta 15 staining intensity may be a potentially important marker to identify hig h-risk patients with moderately differentiated, clinically localized prosta te cancer. UROLOGY 55: 635-638, 2000. (C) 2000, Elsevier Science Inc.