Key Points

• Femara (generic name: letrozole) more commonly causes hair thinning rather than total hair loss. Hair loss is also known medically as alopecia.
• In clinical studies with Femara, when compared with other breast cancer treatments that may also cause hair loss, about 3.4% to 6.2% of women taking Femara reported hair loss of varying degrees. Most hair thinning or loss was not graded as a serious effect.
• Other side effects due to Femara (greater than 20%) may include hot flashes and flushing, joint pain, weakness, fluid retention, headache, dizziness, high cholesterol, sweating increased, and bone or muscle pain, among others.
• Always discuss side effects with your doctor, especially with any new or worsening side effects.

Femara (generic name: letrozole) is a tablet form of hormone therapy known as an aromatase inhibitor. AIs are often used to lower breast cancer recurrence for women treated for hormone-receptor positive breast cancer. It works in breast cancer by reducing the amount of estrogen in postmenopausal women. In general, complete hair loss does not occur with aromatase inhibitors like Femara; however, hair thinning has been reported.

Other aromatase inhibitors (AIs) includes drugs such as anastrozole (Arimidex) and exemestane (Aromasin).

Estrogen loss due to these products may lead to hair thinning or hair loss. Some women may see hair thinning in the first year of treatment that may improve after over time. However, some women may see continued hair thinning but usually not full hair loss. Your hair will typically grow back once you stop treatment with an AI.

Studies of hair loss or thinning with Femara

Studies conducted by the manufacturer of Femara were evaluated to assess hair loss compared with other breast cancer treatments.

Femara vs. tamoxifen

• In a large study of women with early breast cancer using either Femara (2448 women) or tamoxifen (2447 women), the median treatment time was 60 months and the median time women were followed for side effects was 96 months.
• Hair loss or thinning (alopecia) was reported in 3.4% of women (3.4 out of every 100 women) taking either Femara or tamoxifen. However, no cases were rated as serious (Grade 3-4).

Femara vs. anastrozole

• When Femara (in 2049 women) was compared to anastrozole (in 2062 women), another aromatase inhibitor, hair loss or thinning (alopecia) was reported in 6.2% (6.2 out of every 100) of women taking Femara compared to 6.5% of women taking anastrozole.
• The median duration of treatment was 60 months for both treatment arms. Most reactions were reported as mild to moderate, with only 0.1% of women (2 out of 2049) taking Femara having hair loss that was graded as serious (Grade 3-4).

Aromatase inhibitors in general (retrospective study)

• A survey-based, retrospective research study was conducted in 851 female breast cancer survivors who had taken aromatase inhibitors (AI). Women were asked about their hair thinning or hair loss, health habits, use of AIs, and demographic data such as age.
• The results showed that 22.4% (22.4 out of every 100) of the breast cancer survivors reported hair loss and 31.8 % reported hair thinning. Use of an AI at the time of the survey and prior use were significantly associated with hair thinning, but not hair loss.
• These results were found to be independent of use of chemotherapy and age (both of which could also increase the risk of hair loss).

The authors conclude that a reduction in estrogen levels due to AI treatment was associated with an increased risk of hair thinning and hair loss.

Bottom Line

• Complete hair loss with the aromatase inhibitor Femara (generic name: letrozole) used for breast cancer was not reported as a common side effect in randomized, controlled studies conducted by the manufacturer. However, other survey-based studies have suggested hair thinning may be more common than previously reported.
• In general, studies from the manufacturer show that mild-to-moderate hair thinning or hair loss (alopecia) occurs in roughly 3.4% to 6.2% of women receiving Femara over at least 60 months. However, higher rates in the range of 20% to 30% have been reported in retrospective studies looking at AIs in general.
• If you are experiencing hair thinning or hair loss that is troublesome for you, you might consider talking with your doctor about your options. However, most aromatase inhibitors are linked with some level of hair thinning. Once treatment with aromatase inhibitors is stopped, your hair will usually grow back to its normal thickness.

This is not all the information you need to know about Femara (generic name: letrozole) for safe and effective use. Review the full Femara information here, and discuss this information with your doctor or other health care provider.