Women using hormone replacement therapy (HRT) based on a combination of female sex hormones such as estrogen and progestin may be at increased risk of lung cancer, according to a study in the Journal of Clinical Oncology.
The risk of HRT increases the longer it is used – it is highest for women who have been doing it for 10 years or more.
So far, scientists have not been able to define the maximum safe period of using HRT.
Hormone replacement therapy is used in women during menopause (also known as perimenopausal) to alleviate the unpleasant ailments associated with it. Estrogen is expected to reduce symptoms such as hot flashes and vaginal dryness, and to reduce the risk of osteoporosis, i.e. progressive bone loss. In turn, progestogen (a derivative of progesterone) is expected to reduce the risk of estrogen-related cancers, such as breast cancer and endometrial cancer.
For many years, there has been ongoing debate as to whether the benefits of HRT justify its use, taking into account the health risks associated with it. For example, studies show that it slightly increases the risk of breast cancer and, on the other hand, it lowers the risk of colorectal cancer. And there are many more pros and cons.
Scientists from Oregon Health and Science University in Portland analyzed data collected on a group of 36.588 women aged 50 to 76 years, i.e. after menopause or in the perimenopausal period. Their health status was followed on average for 6 years. During this period, 344 women developed lung cancer.
Taking into account other factors that influence the risk of this cancer – such as smoking and age – the researchers concluded that the incidence of lung cancer in the group of women taking combined HRT for 10 years or more was twice as often as in the group not using hormones.
The period of using HRT was also related to the stage of cancer development at the time of diagnosis – the longer it was, the more advanced the tumor was.
As Chris Slatore, the researcher, comments, although the number of women using HRT has decreased recently, and doctors do not recommend this therapy – apart from short-term alleviation of menopausal symptoms with it – millions of women may still face an increased risk of lung cancer.
The researcher emphasizes that the risk of developing this cancer associated with HRT is low compared to that associated with smoking.
For now, scientists cannot explain exactly what is the mechanism behind the relationship between HRT and lung cancer (PAP).