Cathepsin D, both a prognostic factor and a predictive factor for the effect of adjuvant tamoxifen in breast cancer. South Sweden Breast Cancer Group.

Cathepsin D is a lysosomal protease implicated in cancer metastasis. Its concentration in breast tumours has also been shown to be of prognostic importance, although to what extent this is subject to lymph node status, the use of adjuvant therapy and menopausal status has not been clearly evaluated. At a cut-off level of 45 pmol/mg protein (61% of the 623 samples were classified as high cathepsin D tumours; immunoradiometric assay), we found cathepsin D to be of prognostic importance only among breast cancer patients with lymph node-positive (N+) disease not treated with adjuvant tamoxifen. When the series was stratified according to cathepsin D content of their tumours, progesterone receptor (PgR) status and lymph node involvement, adjuvant tamoxifen was found to have a significant beneficial effect only among patients with N+ and PgR-positive breast cancer whose tumours had a high cathepsin D content.