Development of New Targeted Therapies for Breast Cancer

Oncologists typically thought of systemic therapies for breast cancer as belonging to one of two categories: either cytotoxic chemotherapy or hormonal therapy. Though this simple approach served well for decades, the recent development of trastuzumab showed its inadequacies. Trastuzumab, neither broadly cytotoxic nor a classic hormonal manipulation, didn’t fit. Thus, a third category, biologic therapy, or alternatively, targeted therapy, emerged. Targeted therapy is a type of medication which blocks the growth of cancer cells by interfering with specific targeted molecules needed for carcinogenesis and tumor growth, rather than by simply interfering with rapidly dividing cells. Though we tend to think of targeting growth signals in cancer as recent developments, perhaps they are not so novel after all. First proposed as adjunctive therapy by Schinzinger in 1889, Beatson introduced ovariectomy into clinical practice in 18961. While hormonal therapy is not traditionally categorized as targeted therapy, the estrogen receptor remains arguably the most important growth factor receptor identified for breast cancer, as adjuvant hormonal therapies have a bigger impact on recurrence and survival than any other treatment.