Health Report:

Breast Cancer & Fish Oil

Lymphedema after Breast Cancer Treatment

Vasectomy & Prostate Cancer Risk

"A critical weekly review of important new research findings for health-conscious readers..."

By, Robert A. Wascher, MD, FACS

Photo of Dr. Wascher

Last Updated:  11/23/2008

The information in this column is intended for informational purposes only, and does not constitute medical advice or recommendations by the author.  Please consult with your physician before making any lifestyle or medication changes, or if you have any other concerns regarding your health.


It is well known that the omega fatty acids present in cold water fish can reduce the risk of heart disease.  Now, new research, performed at the University of Texas in San Antonio suggests that fish oil may be able to inhibit the growth of breast cancer tumors as well.  This research study, just published in the journal Breast Cancer Research & Treatment, used a mouse model of breast cancer to assess the effects of dietary fish oil supplements on breast cancer tumors implanted into laboratory mice, and on human breast cancer cells grown in laboratory cultures. 

Using sophisticated genetic tests, the researchers found that dietary fish oil inhibited genes associated with tumor growth while, simultaneously, increasing the activity of genes associated with tumor cell death.  Regression of the implanted human breast tumors was also observed when mice were fed a diet containing omega fatty acids derived from fish oil.

In order to further evaluate the effects of fish oil on breast cancer cells, the researchers added DHA and EPA, the two active omega fatty acids found in most fish oil supplements, to human breast cancer cells growing in culture dishes.  Once again, the scientists found that fish oil significantly inhibited genes associated with tumor growth, and simulated other genes associated with tumor cell death.  In particular, fish oil appeared to increase the activity of a gene called PTEN, which belongs to a class of genes called tumor suppressor genes. 

The PTEN gene plays a very important role in signaling normal cells to stop dividing when it is inappropriate for them to do so.  PTEN, along with multiple other tumor suppressor genes, also helps to shunt damaged or abnormal cells into a cellular suicide pathway known as apoptosis.  Together, these two protection mechanisms help to prevent uncontrolled cell growth that would, otherwise, result in the formation of tumors.  In many cancers, the PTEN gene becomes inactivated by mutations, resulting in uncontrolled tumor growth, as well as tumor cell resistance to the apoptosis cell suicide pathway.  Interestingly, an inherited mutation that inactivates the PTEN gene is known to cause Cowden’s Syndrome.  People with Cowden’s Syndrome develop multiple benign tumors, or hamartomas, of the GI tract, bones, brain, eyes and urinary tract.  At the same time, this hereditary cancer syndrome is associated with an increased risk of cancers of the breast, thyroid and uterus. 

This study’s finding that fish oil increases the activity of the PTEN gene is a potentially important discovery, as are the other apparent anti-tumor effects of fish oil on other important cancer-associated genes.  However, my enthusiasm for the findings of this study is tempered by the fact that, so far, these anti-tumor effects of fish oil have only been observed in cell cultures and in immune-compromised mice that have been implanted with human breast cancer cells.  As has been, unfortunately, shown in thousands of prior research studies using cultured cancer cells or laboratory animals, there is no guarantee that these same findings will be reproducible in humans.  These exciting findings with a relatively non-toxic dietary supplement should, therefore, now be studied in human patients with breast cancer as a potential complementary therapy, and as a potential cancer prevention agent in women who are at significantly increased risk of developing breast cancer. 



Arm lymphedema, or chronic swelling of the arm, occurs in 10 to 30 percent of women following treatment for breast cancer.  When the lymphatic drainage network in the arm has been disrupted by the surgical removal of armpit lymph nodes by the surgeon, or by radiation therapy to the armpit area (or, sometimes, following both types of treatment), the delicate network of lymphatic vessels that return excess tissue fluid back to the heart can become obstructed.  This lymphatic obstruction can result in chronic swelling of the hand and arm.  Patients with significant lymphedema of the arm, following breast cancer treatment, may experience considerable swelling (edema), heaviness, stiffness and discomfort of the affected hand and arm. 

A newly published study in the journal Breast Cancer Treatment & Research has taken a new look at factors associated with arm lymphedema following breast cancer treatment.  This study was performed by researchers at the University of Southern California, the City of Hope in California, the National Cancer Institute in Bethesda, the Fred Hutchinson Cancer Center in Seattle, and the University of Louisville in Kentucky.

In this study, nearly 500 women who had been diagnosed with preinvasive or invasive breast cancer completed an initial interview with study researchers.  A follow-up interview was then performed, on average, about 4 years later.  The researchers then analyzed the resulting data from these two sets of interviews.

This study confirmed the findings of numerous prior studies that have linked the surgical removal of armpit lymph nodes, obesity, and high blood pressure with chronic arm lymphedema.  In this study, women with high blood pressure were found to have almost two-and-a-half times the risk of developing lymphedema following breast cancer treatment when compared to women who did not have hypertension.  Moreover, this hypertension-associated risk of lymphedema was essentially equivalent to the level of risk associated with the surgical removal of armpit lymph nodes and with obesity, which is a much higher level of risk than has been reported by most prior studies. 

Taken together, the results of this study confirm several previously established risk factors for arm lymphedema following breast cancer therapy, but also suggest that high blood pressure may, by itself, be a more significant risk factor for lymphedema than has been previously appreciated. 

The good news is that there are strategies available to most women that can address these lymphedema risk factors.  Recently, a relatively new surgical technique has been developed, and allows surgeons to remove only one or a couple of lymph nodes (sentinel lymph node biopsy) in the 60 to 70 percent of breast cancer patients whose breast cancer has not yet spread to lymph nodes in the armpit area.  Sentinel lymph node biopsy has been shown to reduce the risk of lymphedema to one-tenth the risk associated with the more radical complete axillary lymph node dissection that was formerly performed on all breast cancer patients.  Likewise, losing excess weight may also reduce the incidence of obesity-associated lymphedema.  The findings of this study also suggest that achieving good control of hypertension may reduce the volume of edema fluid generated in the arms of patients who have undergone breast cancer therapy, and may further reduce the risk of chronic lymphedema.

For additional information on the subject of chronic lymphedema following breast cancer therapy and sentinel lymph node biopsy for breast cancer, please see the following links:







Despite the fact that the majority of scientific evidence suggests no association between vasectomy and the risk of prostate cancer, several previously published studies have raised concerns that men with a family history of prostate cancer, and men who undergo vasectomy at a young age, may be at an increased lifetime risk of developing prostate cancer following vasectomy.  A newly published study in the Journal of Urology adds further weight to prior studies showing that vasectomy is not associated with an increased risk of developing prostate cancer.  This clinical study was performed by scientists at the Fred Hutchinson Cancer Center and the University of Washington.

More than 1,000 men recently diagnosed with prostate cancer were compared to 942 men without prostate cancer.  All of these study volunteers were matched with each other in terms of age, race, and other important factors known to be related to prostate cancer risk. 

Following detailed interviews with all of the men participating in this study, the researchers found absolutely no difference in the number of men in either group who had previously undergone vasectomy.  In both groups of men, 36 percent had previously undergone vasectomy for the purpose of sterilization.  Furthermore, the men who had undergone vasectomy at a young age did not appear to experience any increased subsequent risk of developing prostate cancer when compared to the men who had undergone vasectomy later in life, and when compared to the men who had never undergone vasectomy.

The findings of this clinical study should be reassuring to men who are considering sterilization by vasectomy (at least with respect to their lifetime risk of developing prostate cancer).

Disclaimer:  As always, my advice to readers is to seek the advice of your physician

before making any significant changes in medications, diet, or level of physical activity.

Dr. Wascher is an oncologic surgeon, professor of surgery, a widely published author, and the Director of

 the Division of Surgical Oncology at Newark Beth Israel Medical Center:


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Copyright 2008.  Robert A. Wascher, MD, FACS.  

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Dr. Wascher's Archives:

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9-28-2008:  Publication & Citation Bias in Favor of Industry-Funded Research?

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8-23-2008:  Alcohol Abuse Before & After Military Deployment; Running & Age; Running & Your Testicles

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