What is Letrozole and How Does It Work?

Letrozole is a type of hormone therapy used to treat hormone receptor-positive (HR+) breast cancer, primarily in postmenopausal women. You might see it sold under the brand name Femara. It belongs to a class of drugs called aromatase inhibitors.

To understand how it works, it helps to know a little about HR+ breast cancer. This type of cancer uses the hormone estrogen to grow and multiply. In postmenopausal women, the primary source of estrogen is not the ovaries, but the conversion of androgens (male hormones) into estrogen by an enzyme called aromatase. This process happens mainly in fat tissue, muscle, and the skin.

Letrozole’s job is to block the aromatase enzyme. By blocking this enzyme, it significantly lowers the amount of estrogen in the body. This effectively starves the cancer cells of the estrogen they need to grow, helping to slow or stop the cancer’s progression. It is often used after surgery to reduce the risk of the cancer returning or to treat cancer that has spread to other parts of thebody.

A Detailed Look at the Side Effects of Letrozole

The most prominent question for many patients is about side effects. Because letrozole works by lowering estrogen levels, many of its side effects are related to the absence of this hormone and can feel similar to menopausal symptoms. It is important to remember that not everyone will experience all of these side effects, and they can range from mild to more severe.

Common Side Effects

These are the effects most frequently reported by people taking letrozole. Many of these can be managed with lifestyle changes or support from your healthcare team.

• Hot Flashes and Sweating: This is one of the most common side effects. You may experience sudden feelings of intense heat, flushing, and sweating, including at night (night sweats). Dressing in layers and avoiding triggers like spicy food and caffeine can sometimes help.
• Joint and Muscle Pain: Many people report stiffness and pain in their joints (arthralgia) or muscles (myalgia). This can feel like arthritis and often affects the hands, wrists, feet, and knees. Gentle exercise, stretching, and over-the-counter pain relievers (after consulting your doctor) can provide relief.
• Fatigue: Feeling unusually tired or lacking energy is very common. It’s important to listen to your body, get plenty of rest, and try to incorporate light physical activity, like walking, which can paradoxically boost energy levels.
• Bone Thinning (Osteoporosis): Lower estrogen levels can lead to a loss of bone density over time, increasing the risk of fractures. Your doctor will likely monitor your bone health with bone density scans and may recommend calcium and vitamin D supplements.
• Vaginal Dryness: Reduced estrogen can cause dryness, itching, or discomfort in the vaginal area. Over-the-counter, hormone-free moisturizers or lubricants can be very effective.

Less Common Side Effects

While not as frequent, it’s good to be aware of other potential side effects. Always report any new or worsening symptoms to your doctor.

• Mood Changes: Some individuals may experience mood swings, anxiety, or feelings of depression.
• Hair Thinning: You might notice your hair becoming thinner, though significant hair loss is rare.
• Nausea: Mild nausea can occur, especially when you first start taking the medication. Taking the tablet with food can help.
• Increased Cholesterol: Letrozole can sometimes cause an increase in blood cholesterol levels. Your doctor will monitor this with routine blood tests.
• Dizziness or Headaches: Some people report feeling dizzy or having headaches.

It is crucial to have an open conversation with your oncology team about any side effects you experience. They can offer strategies, medications, or supportive care referrals to help you manage them effectively.

Food Precautions and Diet Recommendations

While taking letrozole, your diet can play a supportive role in managing side effects and maintaining overall health. There are no strict foods you must completely avoid, but there are important considerations.

Focus on Bone Health

Because of the risk of osteoporosis, a diet that supports strong bones is essential.

• Calcium: Aim for plenty of calcium-rich foods. Good sources include milk, yogurt, cheese, fortified plant-based milks (like almond or soy milk), sardines, and dark leafy greens such as kale and broccoli.
• Vitamin D: This vitamin is crucial for helping your body absorb calcium. Your body makes vitamin D from sun exposure, but it’s also found in fatty fish (like salmon and mackerel), egg yolks, and fortified foods like milk and cereal. Many doctors will recommend a vitamin D supplement.

Grapefruit and Letrozole

Unlike many other medications, letrozole does not have a strong, well-established interaction with grapefruit or grapefruit juice. However, because grapefruit can interfere with how the body processes numerous drugs, it is always wisest to check with your doctor or pharmacist specifically about your situation before consuming it regularly.

General Healthy Eating

A balanced diet can help you manage fatigue and support your immune system.

• Lean Protein: Include sources like chicken, fish, beans, and lentils.
• Fruits and Vegetables: Aim for a variety of colorful produce to get a wide range of vitamins and antioxidants.
• Healthy Fats: Foods like avocados, nuts, seeds, and olive oil are beneficial.
• Limit Alcohol: It’s best to limit alcohol consumption, as it can worsen hot flashes and may have other health implications. Discuss safe consumption levels with your doctor.

How to Properly Use Letrozole

Following your doctor’s instructions for taking letrozole is key to its effectiveness.

• Dosage: The standard dose is one 2.5 mg tablet taken once per day.
• Timing: You can take it with or without food, but try to take it at the same time each day to help you remember.
• Missed Dose: If you forget a dose, take it as soon as you remember. However, if it’s almost time for your next dose, just skip the missed one and return to your regular schedule. Do not take two doses at once.
• Duration: Letrozole is typically prescribed for five to ten years as part of adjuvant therapy (treatment after initial surgery) to help prevent cancer recurrence.

Always speak with your healthcare provider before stopping or changing how you take any prescribed medication. They are your best resource for personalized medical advice.

Frequently Asked Questions

What is the most common side effect of letrozole? The most frequently reported side effects are hot flashes and joint pain. Many people describe the joint pain as feeling stiff and achy, particularly in the morning.

Can I take letrozole if I am not yet in menopause? Letrozole is typically used for postmenopausal women. In some cases, it may be given to premenopausal women, but it would be combined with other medications that suppress ovarian function.

How long does it take for side effects to start? Side effects can begin within a few weeks to a few months of starting the medication. Some may lessen over time as your body adjusts, while others, like bone density loss, are cumulative.