PGR and neoplasm: The association found between serum PN levels and tumor PgR expression (higher serum PN levels were associated with a poorer survival outcome in patients with PgR-poor tumors but not in those with PgR-rich tumors) could again be explained by the putative confounding effect of systemic therapy, since adjuvant endocrine therapies were commonly given to patients with PgR-positive tumors.