Two years of extended anastrozole therapy proved as effective as five years in clinical trial

December 7, 2017

Postmenopausal women with hormone-receptor positive (HR-positive) breast cancer who took the aromatase inhibitor anastrozole for two years after an initial five years of adjuvant endocrine therapy received an equal benefit to those who took the drug for five additional years. The trial results suggest that a shorter duration of treatment may provide sufficient benefits while protecting women from harmful side effects, according to data from the ABCSG-16 phase III trial presented at the 2017 San Antonio Breast Cancer Symposium, held Dec. 5–9.

"In early-stage HR-positive breast cancer, the risk of relapse persists despite many advances in treatment," said Michael Gnant, MD, FACS, director and chairman of the Department of Surgery, Comprehensive Cancer Center, at the Medical University of Vienna. "Adjuvant treatment with aromatase inhibitors has been demonstrated to improve disease-free survival of postmenopausal with this subtype of breast cancer. However, the optimal duration of extended AI has previously been unknown. Because this treatment leads to prolonged side effects and impacts quality of life, it is important to establish how long the treatment should be given."

In this trial, between February 2004 and June 2010, 3,484 with HR-positive were randomized in 71 centers in Austria to receive either two years or five years of extended adjuvant therapy. All had undergone an initial five years of adjuvant endocrine treatment, either tamoxifen or other regimens containing .

The trial's primary endpoint was disease-free survival. Secondary endpoints included overall survival, contralateral breast cancer ( in the opposite ), fractures, and toxicity.

As of June 30, 2016, 78 percent of women in both trial arms were alive without recurrence; 757 women experienced recurrence, relapse, or other disease-free survival events: 377, or 22 percent, of women in the two-year group and 380, or 22 percent, of women in the five-year group.

There was also no significant difference in overall survival or time to contralateral . Bone fractures were more likely in years three to five after randomization, suggesting that a longer duration of anastrozole treatment may be a risk factor for fractures.

Gnant said the trial results suggest that clinicians should consider a two-year course of anastrozole sufficient for most patients.

"I believe that these trial results should be implemented into daily practice at once," Gnant said. "There is simply no rationale to keep most patients on extended AI for longer than two years. This result can help save a lot of unnecessary side effects for many women around the world."

In addition to bone fractures, other side effects of prolonged AI therapy include , hot flashes, arthralgia, sexual dysfunction, and hair loss.

Gnant cautioned that researchers cannot rule out benefits for some patients who take anastrozole for longer periods. He said future translational research using data and biomaterial from the patients in the ABCSG-16 trial could be useful to characterize potential molecular factors that influence patients' response to anastrozole.

Explore further: Denosumab improves disease-free survival for postmenopausal patients w HR+ breast cancer

Related Stories

Denosumab improves disease-free survival for postmenopausal patients w HR+ breast cancer

December 9, 2015
Adding denosumab to adjuvant aromatase inhibitor therapy improved disease-free survival for postmenopausal patients with early-stage, hormone receptor (HR)-positive breast cancer, according to results from the phase III ABCSG-18 ...

New health guidance on breast cancer

November 21, 2017
In their draft guidance, the National Institute for Health and Care Excellence (NICE) said that postmenopausal women with a family history of breast cancer should now be offered the drug anastrozole, and not tamoxifen, to ...

Adjuvant Trastuzumab did not improve outcomes for patients with HER2-low breast cancer

December 6, 2017
Adding trastuzumab (Herceptin) to standard adjuvant chemotherapy did not improve invasive disease–free survival for patients with early-stage breast cancer found to have low levels of HER2, as defined as immunohistochemistry ...

Abemaciclib initial therapy improves outcome in endocrine-sensitive advanced breast cancer

September 11, 2017
The results of the MONARCH 3 trial, presented at the ESMO 2017 Congress in Madrid, showed that adding the cyclin-dependent kinase (CDK) 4/6 inhibitor abemaciclib to endocrine therapy improved progression-free survival compared ...

No significant differences in recurrence rates among women with DCIS taking anastrozole or tamoxifen

December 11, 2015
Postmenopausal women with ductal carcinoma in situ (DCIS) had similar outcomes with disease recurrence whether they took tamoxifen or the aromatase inhibitor anastrozole for five years after surgery, but women in the two ...

Anastrozole prevents recurrence more than tamoxifen in some with noninvasive breast cancer

June 1, 2015
Anastrozole provides a significant benefit compared with tamoxifen in preventing recurrence after a lumpectomy and radiation therapy in postmenopausal women ages 60 years or younger who had DCIS (ductal carcinoma in situ), ...

Recommended for you

Cancer immunotherapy may work better in patients with specific genes

December 15, 2017
Cancer cells arise when DNA is mutated, and these cells should be recognized as "foreign" by the immune system. However, cancer cells have found ways to evade detection by the immune system.

Scientists pinpoint gene to blame for poorer survival rate in early-onset breast cancer patients

December 15, 2017
A new study led by scientists at the University of Southampton has found that inherited variation in a particular gene may be to blame for the lower survival rate of patients diagnosed with early-onset breast cancer.

'Bet hedging' explains the efficacy of many combination cancer therapies

December 14, 2017
The efficacy of many FDA-approved cancer drug combinations is not due to synergistic interactions between drugs, but rather to a form of "bet hedging," according to a new study published by Harvard Medical School researchers ...

Liquid biopsy results differed substantially between two providers

December 14, 2017
Two Johns Hopkins prostate cancer researchers found significant disparities when they submitted identical patient samples to two different commercial liquid biopsy providers. Liquid biopsy is a new and noninvasive alternative ...

Testing the accuracy of FDA-approved and lab-developed cancer genetics tests

December 14, 2017
Cancer molecular testing can drive clinical decision making and help a clinician determine if a patient is a good candidate for a targeted therapeutic drug. Clinical tests for common cancer causing-mutations in the genes ...

Scientists unlock structure of mTOR, a key cancer cell signaling protein

December 14, 2017
Researchers in the Sloan Kettering Institute have solved the structure of an important signaling molecule in cancer cells. They used a new technology called cryo-EM to visualize the structure in three dimensions. The detailed ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.