This story is a supplement to our feature "New Breast Cancer Treatments Help Sufferers Gain Ground" which was printed in the June 2008 issue of Scientific American.

Doctors started aggressively treating breast cancer in the 19th century, with the first mastectomy performed in 1882. But insights into mechanisms driving the disease that would lead to increasingly targeted therapies began with discoveries in the 1950s.


  • Hormonal cancer connection suggested when physicians report significant regression of breast cancer tumors following ovary removal or onset of menopause.
  • 1896: First ovary removal performed as a breast cancer treatment by George T. Beatson.


  • 1951: Estrogen and testosterone found to drive the growth of breast and prostate cancers, respectively.
  • 1958: Cancer researchers identify additional “growth factor” proteins that help tumors thrive.
  • 1966: Estrogen receptor identified.


  • 1976: Cancer-promoting “oncogenes” first discovered in mammals.
  • 1976: Clinical trials begin to show that lumpectomy with radiation can be as effective as mastectomy.
  • 1977: Hormone-blocking drug tamoxifen approved in U.S. for treatment of breast cancers sensitive to estrogen or progesterone.
  • 1988: Trial results show that preoperative chemotherapy shrinks tumors, making less invasive surgeries possible.


  • 1994: BRCA1 gene, known to increase susceptibility to breast cancer, is isolated.
  • 1997: Letrozole, which blocks estrogen synthesis, approved in U.S. for patients whose cancer did not respond to tamoxifen.
  • 1998: Trastuzumab, the first molecular-targeted cancer therapy, approved in U.S. for use in breast cancer.
  • 2007: Lapatinib, an inhibitor of growth signaling, approved in U.S. for use in breast cancer.
  • 2008: Bevacizumab, an inhibitor of blood vessel formation in tumors, approved in U.S. for use in breast cancer.