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Estrogen Replacement Therapy and Breast Cancer

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Is estrogen replacement therapy implicated to triggering breast cancer in women? The answer is yes as there’s a connection between estrogen and breast cancer. In one sentence, we can say that women who undergo ERT post menopause might become vulnerable to breast cancer.

Therefore, we need to understand the link between estrogen and its potential role in causing breast cancer.

Role of estrogen

Estrogen is secreted naturally by the ovaries but in very small quantity in breasts, liver and adrenal glands. Ovaries stop producing estrogen after menopause and thereby many women undergo ERT to regularize estrogen levels in the body and to get rid of post menopause side effects.

The science behind Estrogen Induced Breast cancer

Your body contains both healthy cells and cancerous cells. Breast cancer happens due to proliferation and abnormal growth of these cancerous cells or by multiplying the number of those special types of cells that had already been mutated (had become cancerous) due to various reasons.

So how does this happen? Technically speaking, the breast cells contain estrogen receptors, which are nothing but protein molecules sensitive to estrogen. Such receptors get stimulate on receiving estrogen molecule and thus, they get triggered to multiply malignantly. The estrogen further travels through the bloodstream, attaching to cancerous cells; thereby causing them to multiply randomly and ultimately leading to cancer. It might induce DNA mutation in the normal cells, thereby making them cancerous. The tumours formed due to accumulation of cell mass are called “estrogen-responsive tumors”

Apart from this, estrogen may also stimulate other hormones that play a critical role in development of breast cancer.

Is ERT advised to Breast Cancer Survivors?

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After performing huge number of case studies and clinical trials, doctors have concluded that ERT must be avoided in breast cancer survivors. This is because exposure to estrogen may potentially can cause recurrence of the disease.

This is again supported by evidence from the HABITS - hormonal replacement therapy after breast cancer study in 2004, where an open trail was conducted on women. Scientists concluded that, “cancer survivors on HRT were more likely to develop a new or recurrent breast cancer.” Therefore, doctors are totally apprehensive about treating breast cancer survivors with HRT.

Evidence shows that ERT carries high risks of Breast Cancer in Menopausal and Non-menopausal women also

The reason behind occurrence of ERT related breast cancer has already been explained above. A study conducted by Women's Health Initiative (WHI) involving more than 16,000 healthy women showed “the risks of combined HRT with estrogen plus progestin outweigh the benefits”.

However, development of breast cancer is dependent on the duration of estrogen exposure and whether the therapy is uninterrupted or obstructed. Estrogen –only HRT elevates breast cancer risks only if used for more than 10 years i.e. long term use. Women who are highly vulnerable belong in this category - early menarche, post menopausal and late child bearing, i.e. above 30 years of age.

Combined ERT or Estrogen-Progestin Therapy (EPT) has higher risks than only ERT

Women who take EPT are at higher risks than who had undergone only ERT. As seen on mammograms, such women had increased breasts density. This made it difficult to detect the cancer on the mammogram. The cancer may also get detected at an advanced age.  

So, at this moment we can say that the solution to ERT induced breast cancer is yet to be discovered. All you can do for safety of your health is- consulting properly with your doctor and understanding things clearly before jumping into any decision.

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Written by: Saptakee sengupta
Date last updated: January 04, 2015