The biological basis for the use of an anti-androgen and a 5-α-reductase inhibitor in the treatment of recurrent prostate cancer: Case report and review

Although many prostate cancer cases relapse to a hormone-insensitive state, endocrine therapy involving androgen depletion by orchiectomy or by treatment with LHRH-analogue as well as blockade of the androgen receptor (AR) with anti-androgens remains a primary treatment option. Quality of life (QOL) however, is a prime consideration of men choosing such an approach. In this report we discuss a synergistic combination of 150-mg bicaltumide (Casodex) and 5 mg finasteride (Proscar) in the treatment of a 69-year-old patient with a relapsed (biochemical failure) Gleason score 7 prostate cancer, initially treated with external beam radiation therapy. A successful clinical outcome as evidenced by undetectable serum PSA, bone scan density and overall general well-being was accomplished with minimal side effects. Experiments using an established hormone-dependent prostate cancer cell line (LNCaP) showed that the combination of bicaltumide-finasteride at the same ratio as used clinically, produced synergistic effects on the inhibition of cell proliferation and AR expression/phosphorylation. A more complete inactivation of the AR on this regimen may have had the effect of constraining the ability of the AR to mutate, and/or diminishing the ability of androgen independent clones to evolve. Thus, passage to androgen independence may have been slowed or arrested.