2002 Oncology Program Annual Report

Hormone therapy for postmenopausal women has enjoyed steadily increasing popularity for the last 30 years. Initial excitement for estrogen use diminished in the 1960's when investigators demonstrated an increase in occurrence of endometrial cancer. The increase incidence compared to nonusers was dramatic, about 800%. Fortunately, the cancers were not aggressive and few women died as a result. Progesterone, nearly always medroxyprogesterone, was added to treatment regimens with subsequent return of risk levels to normal. Several studies even suggested some protection and this was seen in the recent Women's Health Initiative (WHI) study. Over the last 20 years studies on breast cancer have given variable results but none showed large risk with hormone therapy. Recent studies have suggested a 20-30% increased risk of breast cancer in women using combined therapy with both estrogen and progesterone but very little increase with estrogen alone. Studies investigating risks of breast cancer mortality have failed to show added risk with hormone therapy and even suggest the opposite. Four large non-randomized studies have suggested a large decrease in colorectal cancer in hormone users, as high as 50%. This was confirmed in the recent WHI report, a randomized prospective and blinded study.

The new information on cancer mortality presented by the WHI study and HERS study agree. Both studies show no increased risk of overall cancer deaths associated with combination hormone therapy. Unopposed use of estrogen at standard dosages is still associated with a significant increase in endometrial cancer as is use of Tamoxifen, a modified estrogen used in chemoprophylaxis for breast cancer. This risk is not seen with raloxifene. Although previous studies failed to suggest any correlation, several recent studies have suggested a small increase risk of ovarian cancer in women on long term therapy with estrogen. The effect at most is small and needs more careful prospective evaluation.