Guinea pigs are cute, furry little animals. Described as docile, easy to care for, and responsive to handling, guinea pigs have been a popular household pet since their introduction to western Europe in the 16th century (from their native South America).
Guinea pig is also the colloquial expression for the subject of an experiment. These animals were widely used for scientific research beginning in the 17th century right up into the 20th century, when they were generally replaced by “lab rats” and mice.
Are you a guinea pig?
If you’re taking an aromatase inhibitor right now, the answer is probably yes.
Now, don’t go ballistic on me here. I’m not saying you’re being victimized by unscrupulous researchers or drug companies testing their experimental drugs on human subjects: on you. All I’m saying is that all of us involved in cancer treatment walk a tightrope: drug companies, physicians, and patients. We want drugs that work. We want to take something that keeps our cancer at bay, that stops its spread or neutralizes it, even if only for a little while. We also want a drug without vicious, unbearable side effects. AND we want a drug without long-term side effects–the heart damage 5 years down the road, another type of cancer in 15 years. AND we want all three of those guaranteed. Guess what? It’s not likely. It may not even be possible.
Tamoxifen, developed in the 1950s as a possible birth control agent, has been approved for use in the U.S. since 1977 as a drug treatment for women with estrogen-receptive breast cancer. It now has a 30-year history of use. And yet, there’s still not complete agreement on its short-term side effects. Does it cause weight gain, as so many women claim, or not? We all–patients, doctors, and its manufacturer, AstraZeneca–agree that tamoxifen can cause hot flashes, vaginal dryness, endometrial cancer, thinning hair, loss of libido, and a range of other effects. But weight gain? No agreement on that one. After 30 years, the jury’s still out.
Now take aromatase inhibitors: Arimidex, Femara, and Aromasin, routinely prescribed to prevent recurrence in postmenopausal women with early stage breast cancer. The first large clinical study (one that showed such positive results that AIs are in the process of replacing tamoxifen for many women) began in 1999 and concluded in 2004. AIs don’t have a 30-year history. At this point, they don’t even have a 10-year history. We’re all learning as we go.
“Tamoxifen has been around 20-30 years and has a long track record. We know about its benefits and its risks,” notes Dr. N. Lynn Henry of the University of Michigan Medical School, one of the researchers in a study examining AI side effects. “Aromatase inhibitors are new, and we don’t have as much experience with them. We have to see in the long term which one ends up being better,” she concludes.
