Prognostic significance of immunohistochemical analysis of cathepsin D in low-stage breast cancer.

Cathepsin D is an estrogen-regulated lysosomal protease that may be overexpressed in breast cancer. Several studies based on biochemical analysis of tumor cytosol have shown that high levels of cathepsin D are associated with poor outcome in patients with breast cancer. In contrast, a few immunohistochemical studies have shown that cathepsin D positivity in breast cancer cells indicates a favorable prognostic outcome or is of no prognostic significance. Because of the current controversy, the authors studied, using immunohistochemistry, the distribution (0 to 3) and intensity (0 to 3) of cathepsin D in Stage I and II infiltrating ductal carcinoma of the breast from 245 patients treated at the City of Hope National Medical Center, Duarte, California, from 1970 to 1986. A commercially available rabbit antiserum to purified human cathepsin D and the standard avidin-biotin complex method were used. Statistical analysis was based on a combined low (0 or 2) or high (3 to 6) score. A high cathepsin D score was associated with Stage II disease (P = 0.007), positive lymph nodes (P = 0.019), high nuclear grade (P = 0.005), and c-erbB-2 oncogene amplification (P = 0.013). Cathepsin D positivity was not an independent prognostic indicator of disease-free survival (DFS) or overall survival (OS). In a subgroup analysis, the presence of cathepsin D had only a modest association with predicting a shorter DFS in patients with negative lymph nodes (P = 0.072) or positive progesterone receptors (PR) (P = 0.086). Immunohistochemical analysis of cathepsin D, with the antiserum used in this study, is not an independent predictor of outcome in patients with breast cancer because of its strong associations with several well-established prognostic indicators.