From the Guidelines
Anastrozole is generally considered safe before surgery, but the decision to continue or pause it should be made by your healthcare provider based on your specific situation. Typically, anastrozole, an aromatase inhibitor commonly used for breast cancer treatment, does not need to be stopped before most surgical procedures 1. The standard dose is 1 mg taken orally once daily. Unlike medications that affect blood clotting, anastrozole doesn't increase bleeding risk during surgery. However, your surgeon and oncologist should coordinate care to determine if any temporary discontinuation is needed for your specific procedure. This is particularly important if you're taking anastrozole as part of breast cancer treatment and are planning breast surgery.
Some key points to consider:
- Anastrozole works by reducing estrogen production in postmenopausal women, which can slow or stop the growth of certain breast cancer cells 1.
- The use of either anastrozole or letrozole alone provides superior rates of breast-conserving surgery and usually objective response when compared with tamoxifen 1.
- If preoperative endocrine therapy is to be used, an aromatase inhibitor is preferred in the treatment of postmenopausal women with hormone receptor–positive disease 1.
- Your healthcare provider should be informed about all medications you're taking, including anastrozole, when planning for surgery.
In terms of management,
- Some surgeons may recommend continuing anastrozole right up to surgery day and resuming it as soon as you can take oral medications afterward, while others might suggest a brief pause 1.
- Postoperative treatment for these patients consists of individualized chemotherapy, and endocrine therapy after chemotherapy in women with ER- and/or PR-positive tumors 1.
- Up to 1 year of trastuzumab therapy should be completed for HER2-positive tumors (category 1) 1.
It's essential to follow the guidance of your healthcare provider, as they will consider your specific situation and make recommendations based on the most recent and highest-quality evidence available 1.
From the Research
Safety of Anastrozole Before Surgery
The safety of anastrozole before surgery can be evaluated based on its pharmacological properties and clinical trial data.
- Anastrozole is an aromatase inhibitor that reduces estrogen levels in postmenopausal women, which can help reduce the growth of hormone receptor-positive breast cancer cells 2.
- Clinical trials have shown that anastrozole is generally well-tolerated, with common adverse events including gastrointestinal disturbances, hot flushes, and bone pain 3.
- A study published in 2023 found that extending anastrozole treatment for an additional 5 years after initial treatment was well-tolerated and improved disease-free survival in postmenopausal patients with hormone receptor-positive breast cancer 4.
- However, another study published in 2025 reported a rare case of anastrozole-induced interstitial lung disease, highlighting the potential for serious side effects in some patients 5.
Adverse Events Associated with Anastrozole
Adverse events associated with anastrozole include:
- Gastrointestinal disturbances (incidence 29-33%) 3
- Hot flushes and bone pain (both <12%) 3
- Musculoskeletal pain (significantly worse in the anastrozole group compared to the tamoxifen group) 6
- Interstitial lung disease (rare) 5
- Agranulocytosis (rare, but reported in a patient who switched to tamoxifen after developing interstitial lung disease with anastrozole) 5
Comparison with Tamoxifen
- A study published in 2016 found that anastrozole and tamoxifen had similar effects on quality of life and symptoms in postmenopausal patients with ductal carcinoma in situ, but anastrozole was associated with more musculoskeletal pain and vaginal symptoms, while tamoxifen was associated with more vasomotor symptoms and gynaecological symptoms 6.
- The same study found that younger age was significantly associated with more severe vasomotor symptoms, vaginal symptoms, weight problems, and gynaecological symptoms 6.