Breast Cancer Aromatase Therapy

The research I am doing for tonight’s blog is a little overwhelming. I of course, call myself to task to be able to read and comprehend the research well enough to say it here in layman’s terms. Let me begin then by telling you why I am reading about adjuvant hormone therapy for the treatment of breast cancer.

Breast cancer does run in my family, and someone who is very dear to me is now being treated with a medicine called anastrozole or Arimidex, and is upset that this medicine costs more than an older aromatase inhibitor called tamoxifen. She did not want to take any medicine after her mastectomy so the fact that she is taking one is very positive, but before she switches, something her doctor vehemently opposes, I thought I would research the issue.

Let me start by explaining some of the terms I have just thrown at you. An adjuvant is a treatment that is secondary or one that assists. If a person has surgery and then has chemotherapy that is considered adjuvant chemotherapy. Some women, especially post menopausal women, will benefit from hormonal therapy instead of chemotherapy. The purpose is to stop production of estrogen for those with breast cancers that are fed by estrogen. (please see http://www.breastcancer.org/ for details about different types of breast cancer) The incidence of recurrence in breast cancer can be high and is most difficult to treat if that recurrence occurs with in the first 3-5 years. A common problem is breast cancer in the opposite breast or contra lateral breast cancer and distant metastasis. A goal, the goal, of course is DFS or disease free survival.

In researching this issue I learned that recurrence is more common in survivors than breast cancer incidence is in the general public. I also learned that genetics aside, weight, HRT and smoking are risk factors for breast cancer initiation and recurrence. Further more, alcohol in excess of seven glasses a week or any alcohol in combination with tobacco use increase first and recurring risk. My risk factors then are family and past history of smoking.

Now, back to the issues of tamoxifen vs anastrozole. The article that I spent the most time reading included reference to several other peer reviewed scientific studies that are published in scholarly journals. This one is from the J Cancer Res Clin Oncol (2007) with lead author Stefan Paepke.

It is important to know that tamoxifen has been the standard of care and is effective in preventing local recurrence but not distant metastasis which means overall survival is not necessarily improved. Tamoxifen also comes with risk of serious side effects which include stroke, endometrial cancer and blood clots which can lead to pulmonary embolism. The side effect profile is much worse for patients over age 50. The most significant side effect noted for anastrozole is bone loss and patients on this drug may also take a drug like fosomax.

What I am seeing in the literature now is not a question of whether or not AI or aromatase inhibitors are better, but how and when to use them. Some say they should be used immediately after surgery or even instead of surgery in some cases, and studies have shown that switching from tamoxifen after three years is effective in preventing that early recurrence or distant metastasis. It is NEVER suggested that one go from a newer AI to tamoxifen.

The research article I read which again included the results from past trials, wants to answer the question of whether these new AIs are more effective in increasing overall survival by preventing early distant metastasis. Tamoxefin alone for five years has been found in at least one study to reduce that outcome by 41% and mortality by 34%, compared to not taking any adjuvant drug. But again, the side effects related to tamoxifen are serious. The results of the study and the reason I would like my loved one to continue on her medicine are thus:

The AIs, especially aromatase and letrozole are more effective in preventing early distant metastasis. Though the study authors said that there is no good data yet to determine which AI is better, they are all better for this outcome than tamoxifen and should be started as soon after surgery as possible. They did note that letrozole does appear more effective at stopping distant metastasis if used first or initially.

The side effect profiles are worth noting. Oncologists consider AIs safer but they do increase risk of fractures in person who have below normal bone mineral density at start, they also can cause hypercholesterolemia or high cholesterol and thus effect cardiovascular health.

Wow. Again, I am just overwhelmed. The article does not address cost difference between the older tamoxifen and the AIs which can be 400 dollars. With my public health hat on, however, I believe that the AI is the better medicine for estrogen positive breast cancer survivors.