After surgery, women diagnosed with hormone-receptor-positive breast cancer usually take hormonal therapy medicine to reduce the risk of the cancer coming back (recurrence). Hormonal therapy given after surgery is called adjuvant hormonal therapy.
Hormonal therapy medicines work in two ways:
- by lowering the amount of estrogen in the body
- by blocking the action of estrogen on breast cancer cells
There are several types of hormonal therapy medicines. Tamoxifen, a selective estrogen receptor modulator (SERM), is one of the most well-known. Tamoxifen can be used to treat both premenopausal and postmenopausal women. In the early 2000s, the aromatase inhibitors:
- Arimidex (chemical name: anastrozole)
- Aromasin (chemical name: exemestane)
- Femara (chemical name: letrozole)
were shown to be more effective at reducing recurrence risk in postmenopausal women and are now used more often than tamoxifen to treat women who’ve gone through menopause. Aromatase inhibitors aren’t used to reduce recurrence risk in premenopausal women.
In 2012 and 2013, large studies found that 10 years of tamoxifen was better than 5 because it:
- lowered the incidence of breast cancer coming back (recurrence)
- reduced the number of deaths from breast cancer
- improved overall survival
So researchers wanted to know if taking an aromatase inhibitor for 10 years would offer more benefits than taking one for 5 years.
A study has found that taking Femara for 10 years instead of 5:
- reduces the risk of recurrence
- reduces the risk of a new breast cancer being diagnosed in the opposite breast (contralateral breast cancer)
The research was published online on June 5, 2016 by the New England Journal of Medicine and presented at the 2016 American Society of Clinical Oncology Annual Meeting on June 6, 2016:
- Read “Extending Aromatase-Inhibitor Adjuvant Therapy to 10 Years,” in the New England Journal of Medicine
- Read the abstract of “Patient-reported outcomes from MA.17R: A randomized trial of extending adjuvant letrozole for 5 years after completing an initial 5 years of aromatase inhibitor therapy alone or preceded by tamoxifen in postmenopausal women with early-stage breast cancer.” presented at the ASCO Annual Meeting
The study included 1,918 women diagnosed with early-stage, hormone-receptor-positive breast cancer. All the women had been treated with surgery and 5 years of Femara or another aromatase inhibitor and none of the women had had a recurrence.
The women ranged in age from about 60 to about 72 years old. About 80% of them were treated with tamoxifen before they were treated with 5 years of an aromatase inhibitor.
The women were randomly assigned to receive one of two treatments:
- 5 years of Femara, for a total of 10 years of an aromatase inhibitor
- 5 years of a placebo (a sugar pill that looked just like Femara)
After about 6 years of follow-up, 165 women had either a breast cancer recurrence or a new breast cancer in the opposite breast:
- 67 women were taking Femara
- 98 women were taking the placebo
When the researchers analyzed these numbers, they found that the 5-year disease-free survival rate was:
- 95% for Femara
- 91% for the placebo
This difference was statistically significant, which means that it was likely because of the difference in medicine and not just due to chance.
Five-year disease-free survival rates are the percentages of women who lived for 5 years without the cancer coming back.
When the researchers looked specifically at the rates of contralateral disease, they found a big difference between the two groups:
- 13 women taking Femara were diagnosed with breast cancer in the opposite breast
- 31 women taking the placebo were diagnosed with breast cancer in the opposite breast
Again, this difference was statistically significant.
There was no difference in overall survival between the two groups. Overall survival is how long a woman lives, with or without the cancer coming back.
Paul Goss, M.D., Ph.D., of Massachusetts General Hospital Cancer Center, the lead researcher of the study, said in an interview that the results are sufficiently strong that most postmenopausal women who have taken an aromatase inhibitor for 5 years should continue for another 5 years.
“If the patient is tolerating the aromatase inhibitor well, the quality of life is good, and the recent bone mineral density is good, why not?” he said.
Like all hormonal therapy medicines, Femara can cause side effects, including bone thinning and weakening, a higher-than-average risk of broken bones, fatigue, bone and joint pain, and hot flashes.
In this study, women taking Femara had more bone pain, broken bones, and newly diagnosed osteoporosis compared to women taking the placebo. Still, the number of women who had these side effects was relatively low. The researchers said this was because women who had unacceptable side effects while taking Femara for the first 5 years were unlikely to have signed up for the study.
“These are highly selected patients,” said Dr. Goss, “who are not the ones who are having very severe symptoms who have typically dropped out before.”
“Five more years of Femara will prevent some breast cancer recurrences, but possibly at the cost of more broken bones, which can be serious in older women,” said Brian Wojciechowski, M.D., medical oncologist and Breastcancer.org medical adviser. “After the first 5 years, I plan to offer an extra 5 if the patient is doing well on the drug and she feels the benefits are worth the risks.”
If you’ve been diagnosed with early-stage, hormone-receptor-positive breast cancer and are finishing up 5 years of an aromatase inhibitor, you may want to ask your doctor about this study and whether taking Femara for another 5 years (for a total of 10 years of an aromatase inhibitor) makes sense for you. Talk to your doctor about any side effects you’ve been having and whether the benefits of another 5 years of Femara outweigh the risks of side effects. Together, you can decide on a treatment plan that’s best for YOU.