Highlights of abstracts on hormone-refractory prostate cancer presented at the 1996 Annual Meeting of the American Society of Clinical Oncology

Among the more interesting studies at the 1996 annual meeting of the American Society of Clinical Oncology that related to hormone-refractory prostate cancer were several that reported on the use of cis-retinoic acid both alone and in combination with interferon-α. Interferon-α and interferon-α plus cis-retinoic acid have antiproliferative effects in vitro against both PC3 and D-145 prostate cancer cells in culture. BCL2 expression is increased in androgen-independent cells, which may block apoptosis, and retinoids induce transforming growth factor-β and apoptosis in prostate cancer cell lines. This regimen raises many questions. For example, it is difficult to determine what prostate-specific antigen (PSA) level one should expect from cis-retinoic acid, 4HPR, or any of the other differentiating agents. Should there be an increase in PSA? Should one expect a slower decline in PSA when giving additional agents that are in fact cytotoxic? What is the significance of a changing level of PSA after this and other types of treatment? These and other questions remain to be determined in future studies.