Overweight Women At Risk Of Breast Cancer Recurrence

Obesity has been blamed for a huge number of diseases that plague mankind. Some of the major categories of diseases, namely the cardiovascular diseases, diabetes and cancer have also been linked to obesity.

It is a long known fact that obese women run a higher risk of developing breast cancer. However, an important research study, which was published in the journal Cancer, a peer reviewed journal of the American Cancer Society, has found that the risk of recurrence of breast cancer is also higher in obese women.

Research at College of Medicine's Montefiore Medical Center

The research study was led by Dr Joseph Sparano, from the Albert Einstein College of Medicine's Montefiore Medical Center, Bronx, NY, along with his colleagues. They included around 7000 women in their study. All of these women had had stage 1 to 3 breast cancer in the past and had participated in three trials (E1199, E5188, and E3189) run by the National Cancer Institute. Apart from the breast cancer, these women had normal heart, kidney, liver, and bone marrow function and did not suffer from any other significant health problem. 

This criterion was important for the selection of the participants in order to study the effect of obesity on the potential recurrence of breast cancer and the survival rate of the patients. The researchers found that 5000 of these patients had received chemotherapy for their condition which included regimens of doxorubicin and cyclophosphamide as per their body weights. Researchers noted that one third of these 5000 women were obese, while another one third had a body mass index that indicated that they were overweight. Following the chemotherapy treatment, it was seen that the cancer recurred in one-fourth of the women. A total of 891 women lost their lives within eight years of chemotherapy, out of which 695 deaths were due to breast cancer.

Sparano and his colleagues found that obese women had a 40 percent higher risk of suffering from a breast cancer recurrence compared to women with a BMI in the normal weight range. It was also seen that the obese women were 69 times more likely to die. The cause of death could be breast cancer or any other disease.

Another important aspect of this study was that obesity was strongly associated with the recurrence of breast cancer when the tumor was an estrogen receptor (ER) positive type. It is to be noted that ER positive tumors are the most common type of breast cancers, accounting for more than two third of the cases. In other types of cancers, which are not estrogen dependent, the link between obesity and recurrence could not be clearly established.

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".