In the late 1930s Huggins performed orchiectomy or administered estrogens to prostate-cancer patients and observed dramatic drops in serum acid phosphatase and tumour symptoms. The results established the concept of “hormone-sensitive tumours.” His approach showed that a cancer can be controlled by endocrine manipulation rather than radical surgery, greatly improving patients’ quality of life. Later, LHRH agonists and anti-androgen drugs were developed and became standard therapy for prostate cancer. The work also influenced treatments for other hormone-dependent cancers such as breast cancer.

Huggins first showed in dog models that prostate tissue regresses after androgen removal, then translated the finding to clinical practice. By giving patients estrogens he suppressed testosterone production via the hypothalamic-pituitary axis and quantitatively demonstrated a drop in the tumour marker acid phosphatase. His study was one of the earliest to identify a hormone-receptor axis as a cancer driver and to introduce pharmacologic blockade as a new clinical strategy. Today, GnRH analogues, CYP17 inhibitors and second-generation anti-androgens treat even metastatic castration-resistant prostate cancer. Huggins’ idea is viewed as a prototype of targeted and personalised therapy.

Huggins’ clinical studies employed serial acid-phosphatase measurements as outcome metrics, providing biochemical proof of ADT efficacy. He anticipated the mechanism whereby androgen-AR binding activates transcription of PSA and proliferation genes, a concept later exploited by AR-signal blockade therapies. Castration-resistant phenotypes emerging after ADT are now known to arise from AR gene amplification, splice variants and ligand-independent activating mutations. Agents such as the CYP17 inhibitor abiraterone and the AR antagonist enzalutamide counter these mechanisms and significantly improve overall survival. Huggins’ hormone-manipulation paradigm influenced tamoxifen therapy for ER-positive breast cancer and steroid use in autoimmune disease.