Estrogen-Only Hormone Replacement Therapy Could Lower Pancreatic Cancer Risk

By Rachael Rettner, Senior Writer Published: 09/13/2013 10:06 AM EDT on LiveScience

One type of hormone replacement therapy for postmenopausal women may decrease the risk of pancreatic cancer, a new study suggests.

In the study, women from California who took estrogen-only hormone replacement therapy for symptoms of menopause were 41 percent less likely to develop pancreatic cancer over a 14-year period than women who never took hormone replacement therapy.

Estrogen-only hormone replacement therapy (HRT) contains the female hormone estrogen by itself, as opposed to in combination with other hormones, such as progestin. Because estrogen by itself may increase the risk of uterine cancer, estrogen-only HRT is generally prescribed only to women who've had their uterus removed (a hysterectomy).

However, in contrast to the results with estrogen-only HRT, the study also found another type of estrogen-containing medication -- birth control pills -- were linked with an increased risk of pancreatic cancer when used over the long term. [7 Surprising Facts about The Pill]

Women who took oral contraception for 10 years or more had a 72 percent greater risk of developing pancreatic cancer than those who had never used oral contraception.

The study found associations, and cannot prove that estrogen -- whether in hormone replacement therapy or birth control pills -- actually causes an increase or decrease in pancreatic cancer risk. Factors not taken into account by the researchers may be responsible for the links.

In addition, pancreatic cancer is rare, so the risk of any woman in the study developing the condition was small.

The reason for the opposite findings is not clear, the researchers said. But they speculate that the formulation and dose of estrogen in the different medications could play a role.

Many birth control pills contain estrogen in combination with progestin, while estrogen-only HRT contains only estrogens.

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Estrogen-Only Hormone Replacement Therapy Could Lower Pancreatic Cancer Risk