Day 1 at the San Antonio Breast Cancer Symposium

Causes of Breast Cancer

When are the epidemiological studies on breast cancer going to catch up to the fact that breast cancer is not one disease?

Dr. Valerie Beral, gave the first presentation on “An epidemiological perspective on the causes and prevention of breast cancer.”  She made broad, sweeping generalizations on how to prevent breast cancer without acknowledging the different subtypes of breast cancer, which more than likely, have different causes.

She compared incidence rates across the world, showing that industrialized coutries have a 6.3% cummulative incidence by age 70, compared to 1% for rural, non-developed areas in Asia and South Africa.  She said that worldwide incidence is going up, but primarily in areas of the world that were less developed but are becoming more Westernized.

She concluded after presenting some historical data that “most if not all” of the international differences can be explained by differences in childbearing, lactation, and obesity.   She then went on to say that the goal to reduce the toll of breast cancer should be to develop a “hormonal vaccine” for early adulthood.

First of all, we now know there are at least five different subtypes of breast cancers and we can’t make broad generalizations about the causes and prevention of breast cancer without recognizing the different types, with different natural histories, and more than likely, different causes.

Secondly, we can’t really know what other factors might be responsible for differences between Westernized vs. non-Westernized areas of the world.  Could environmental factors such as estrogen disrupters in pollutants be a factor?  Could there be dietary factors responsible?

And third, some types of breast cancer are associated with EARLIER pregnancy, and particularly more aggressive types.  We wouldn’t want to give a vaccine that might actually increase the odds of some types of breast cancer.

We clearly need much more information and future epidemiological studies must take into account different types of breast cancer.

Hormonal Therapy

Lots of presentations with no real surprises.  TEAM trial results were presented showing that there was no difference in overall survival or disease free survival in taking tamoxifen and then switching to exemestane (Aromasin) or taking only exemestane.   Another study found that side effects from aromatase inhibitors had no predictive value on outcome after three years of follow-up.  One interesting study did look at premenopausal women who took tamoxifen for five years and then continued on with an aromotase inhibitor if they had become post-menopausal.  The study found a 10% absolute difference in disease free survival for those who took the AI vs those who took a placebo.

There continues to be an issue with these trials comparing AIs vs tamoxifen because they have not taken into account the growing consensus that 5-10% of women on tamoxifen have a polymorphism that is preventing the drug from being metabolized.  This hasn’t been addressed by any of the Pharma companies producing the AIs and presenting results of their trials.

Alcohol and Breast Cancer Recurrence

Results from a Kaiser Permanente study on over 1800 breast cancer survivors were presented showing an association with drinking more than 3-4 drinks a week and recurrence.   The association held after controlling for age, BMI, HR status, total folate intake, tamoxifen use, stage of disease, and lymph node status.  The association was strongest among post-menopausal women and obese women.  No association was found with drinking less than 3-4 drinks per week.

MRI and BRCA 1 and 2

A study in Canada has been following women with BRCA 1 and/or 2 mutations who are at a higher risk of breast cancer, and who are receiving annual MRI screening, and comparing them to women with BRCA 1 and/or 2 mutations who are receiving annual mammograms.  After 10 years they have found a stage shift with MRI screening.  Women who receive the MRIs are being diagnosed with more DCIS and Stage I breast cancer, but less Stage III and Stage IV breast cancer.  This indicates the possibility that MRIs could reduce mortality from breast cancer in women with BRCA 1 and 2 mutations.  Further research is needed in this area.

Bisphosphonates

Bisphosphonates have traditionally been given to women to treat or prevent osteoporosis.  However, interest in the effect of these drugs on breast cancer risk and breast cancer recurrence has increased after some surprise findings that the drugs appear to have an impact on recurrence.  Two observational studies were presented this year that looked at the relationship between oral bisphosphonate use and breast cancer risk.  One study was the large Women’s Health Initiative and the other was a study from Israel.  Both studies found an association with bisphosphonate use and a decrease in breast cancer incidence.  The association held up in both studies after controlling for several factors including bone mineral density and age.

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