Estrogen Or Insulin May Be The Reason Behind Recurrence Of Breast Cancer In Obese Women

Although the important research study was only able to establish a link between obesity and the recurrence of breast cancer in women who already previously battled the cancer, rather than a causal relationship, Dr. Sparano feels that further studies in this direction may prove that obesity is the cause behind the recurrence. His doubt is strengthened on the basis of the fact that obesity was found to be associated with the recurrence of estrogen receptor positive tumors.

It is a known fact that in obese postmenopausal women, peripheral fat serves as a site for the biosynthesis of estrogen. The fat in the peripheral tissues as well as the breast tissue contains a set of enzymes known as “aromatase.”

These enzymes convert the hormones produced by the post-menopausal ovaries and adrenal glands, namely, the androgens, androstenedione and testosterone, into estrogens, estrone and estradiol, respectively. Experts believe that the aromatase enzyme, present in the fat of the breast tissue, can produce local estrogen which is ten times the level of estrogen circulating in the body.

The researchers have further speculated that a similar mechanism may be at play in cases of recurrence of breast cancer in those women who already had this type of cancer before.

According to Dr. Sparano, on comparing the prognosis of women who had a normal or healthy weight with those who are obese, and have received the latest and the best treatment available for breast cancer, the risk of breast cancer recurrence is up by 24 percent and the risk of death due to the disease is up by 37 percent in obese women. 

Dr. Massimo Cristofanilli, the head of medical oncology at the Fox Chase Cancer Center, Philadelphia has speculated that estrogen receptor blocking agents like tamoxifen are not completely successful in obese women because of the exceptionally high levels of estrogen. This may lead to a recurrence of breast cancer. Such women may require a prolonged course of treatment with tamoxifen to overcome the extra estrogen.

Researchers have opined that levels of circulating insulin may also be playing a role in the recurrence of breast cancer in obese women. As women with a BMI above 30 may develop insulin resistance, they have higher levels of insulin. Earlier studies have already shown that insulin can stimulate the growth of cancerous cells in the breast.

The general inflammation associated with obesity may also be associated with the recurrence of breast cancer.

Even in women who were healthy and had a normal body weight at the time they were diagnosed with breast cancer and received the best treatment available, obesity at a later stage was associated with higher risk of recurrence of breast cancer, and subsequent death.

According to the National Cancer Institute, one in every eight women in the United States is likely to be diagnosed with breast cancer at some point of her life. But the risks associated with the disease vary at different points.

According to Dr. Sparano, the risk of recurrence of breast cancer may be reduced by adopting treatment strategies which aim at interfering with the hormonal changes and inflammation associated with obesity. The women who were diagnosed with breast cancer pay maximum attention to get through their chemotherapy and hormonal therapy. However, it would help them a great deal if they pay attention to their weight as well. Women who are obese or overweight may reduce their risk of recurrence of breast cancer by watching their diet and reducing weight, along with abiding with the recommended treatment. Even after a diagnosis of cancer is made, obese women can adapt life style changes which help them to lose weight. This may go a long way in improving their prognosis.

Should doctors advise overweight women to work on weight loss after a breast cancer diagnosis, to prevent recurrence? This data suggests that the answer might well be "yes".