Exposure to Increased Levels of Estrogen can Play an Important Role in the Development of Breast Cancer

The likelihood of a woman developing breast cancer is affected by her age at the time of commencement of her menstrual periods and at the time she attains menopause. Similarly, the age of the woman when she first gives birth to a child, has also been demonstrated as an important risk factor in the development of breast cancer in many epidemiological studies.
 
We all know that the endocrinal environment inside a woman’s body goes for a toss at the time of menarche, menopause and pregnancy. This hormonal upheaval in the three phases of reproductive life of a woman can play an important role in the pathogenesis of breast cancer.

An orderly cyclical pattern of follicular maturation, development of corpus luteum, and its regression associated with specific changes in he levels of different sex hormones leads to menstruation. Women are known to have irregular periods just after menarche and in the years prior to menopause. This occurs because of improper follicular maturation and the impaired corpus luteum can lead to insufficient production of progesterone. The hormonal environment thus produced due to a deficiency of progesterone, is rich in estrogen. Something similar happens in case of delayed menopause. Here again, a woman experiences irregular periods and the hormonal environment thus produced, is rich in estrogen. An involuntary infertility is often the cause of delayed age of first parity. Once again, it is the inadequate production of progesterone during the luteal phase of menstrual cycle which gives rise to involuntary infertility. A progesterone deficient environment means an increased exposure to estrogen.

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As all the three conditions, i.e. early age at menarche, late onset of menopause and a delayed first pregnancy have been associated with a high risk of development of breast cancer, one can infer that exposure to increased levels of estrogen in these conditions can play an important role in the development of breast cancer. Moreover, even if a woman has normal menstrual cycles, an early age at menarche and a delayed onset of menopause means that she experiences more number of menstrual cycles in her reproductive age. This means that she experiences a greater cumulative estrogen exposure. Studies have revealed that women who experience a greater (more than 350) cumulative number of menstrual cycles, have an increased incidence of breast cancer.

The menstrual cycle is also related to the treatment of breast cancer in women. Certain studies have shown that adjuvant surgical oophorectomy during the luteal phase of the menstrual cycle is better than removal of ovaries in the follicular phase. It results in reduced risk of recurrence of the breast cancer during the first 5.5 years of follow up. However, the benefits of luteal phase surgery on the chances of recurrence of breast cancer are not appreciable after 6 years of surgery.

There is still a lot of controversy regarding the benefits of luteal phase surgery for breast cancer as there are many other studies which do not support this view. A lot of work has to be carried out in this field before one can establish the ideal time of breast cancer surgery in relation to the different phases of menstruation.