HRT and Risk of Cancer

Estrogen-progestin therapy (EPT) and cancer risk
Endometrial cancer

• Studies show that EPT does not increase the risk of endometrial cancer  
• It is linked to a higher risk of abnormal vaginal bleeding. 
• Because vaginal bleeding after menopause can be a symptom of endometrial cancer, this often leads to further testing.

Breast cancer

• Based on the WHI study, taking EPT is linked to a higher risk of breast cancer. 
• The longer EPT is used, the higher the risk. The risk returns to that of a woman who never used EPT (the usual risk) within 3 years of stopping the hormones. 
• Breast cancers in women taking EPT are more likely to be found when they are bigger and have spread beyond the breast.
• Taking EPT is also linked to increased breast density (as seen on a mammogram). Increased breast density can make it harder to find breast cancer on a mammogram.

Ovarian cancer

• Risk factors for ovarian cancer are harder to study because it is a less common cancer. 
• The WHI did not find a real difference in ovarian cancer risk with EPT. Although there were more cases of ovarian cancer in the women on EPT, this may have been due to chance because of the small number of women who were affected with this cancer.
• However, a recent analysis combined the results of more than 50 studies, including randomized controlled trials and observational studies. This analysis found that women who took estrogen and progestin (progesterone) after menopause did have an increased risk of getting ovarian cancer. 
• The risk was highest for women taking hormones, and decreased over time after the hormones were stopped.

Colorectal cancer

• In the WHI study of EPT, the results were mixed. 
• Women who took EPT had a lower risk of getting colorectal cancer at all, but the cancers they got were more advanced (more likely to have spread to lymph nodes or distant sites) than the cancers in the women not taking hormones.
• Some observational studies have found a lower risk of colorectal cancer in women taking EPT, but some did not. So far, though, observational studies have not linked EPT with a higher risk of colorectal cancer.

Lung cancer

• EPT is not linked to a higher risk of getting lung cancer, but it is linked to a higher risk of dying from lung cancer.

Skin cancer

• EPT is not linked to a higher risk of any type of skin cancer (including both melanoma and other types of skin cancer).

Estrogen therapy (ET) and cancer risk
Endometrial cancer

• In women who still have a uterus, using systemic ET has been shown to increase the risk of endometrial cancer (cancer of the lining of the uterus). 
• The risk remains higher than average even after ET is no longer used. 
• Although most studies that showed an increased risk wereof women taking estrogen as a pill, women using a patch or high-dose vaginal ring can also expect to have an increased risk of endometrial cancer.
• Because of this increased cancer risk, women who have gone through menopause and who still have a uterus are given a progestin along with estrogen. Studies have shown that EPT does not increase the risk for endometrial cancer.
• Long-term use of vaginal creams, rings, or tablets containing topical estrogen doses may also increase the levels of estrogen in the body. It’s not clear if this leads to health risks, but the amounts of hormone are much smaller than systemic therapies.

Breast cancer

• ET is not linked to a higher risk of breast cancer. 
• In fact, certain groups of women taking ET, such as women who had no family history of breast cancer and those who had no history of benign breast disease, had a slightly lower risk of breast cancer.

Ovarian cancer

• The WHI study of ET did not report any results about ovarian cancer.
• However, a recent analysis combined the results of more than 50 studies, including randomized controlled trials and observational studies. This analysis found that women who took estrogen after menopause did have an increased risk of getting ovarian cancer. The risk was highest for women currently taking estrogen, and decreased over time after estrogen was stopped.
• Observational studies have shown that women who take ET have a higher risk for ovarian cancer compared with women who take no hormones after menopause. 
• The overall risk remains low, but it does increase the longer a woman uses ET. The risk of ovarian cancer goes down after a woman stops taking the hormone.

Colorectal cancer

• In the WHI study, ET did not seem to have any effect on the risk of colorectal cancer.
• Observational studies have found a lower risk of colorectal cancer in women who have used ET for many years.

Lung cancer

• ET does not seem to have any effect on the risk of lung cancer.

Skin cancer

• ET is not linked to a higher risk of any type of skin cancer (including both melanoma and other types of skin cancer).

Reference:
http://www.cancer.org/cancer/cancercauses/othercarcinogens/medicaltreatments/menopausal-hormone-replacement-therapy-and-cancer-risk