Understanding Letrozole: A Guide to Usage, Side Effects, and Diet

For many people with hormone receptor–positive breast cancer, treatment includes more than surgery, chemotherapy, or radiation. Medicines that lower or block estrogen can play a central role in reducing recurrence risk or controlling disease over time. Letrozole is one such medication, and understanding how it is used, what to expect, and how to support your body can make day-to-day treatment feel more manageable.

This article is for informational purposes only and should not be considered medical advice. Please consult a qualified healthcare professional for personalized guidance and treatment.

Breast cancer treatment options and endocrine care

Breast cancer care is often described in categories: local treatments (such as surgery and radiation) and systemic treatments (such as chemotherapy, targeted therapy, immunotherapy, and endocrine therapy). The right mix depends on factors like hormone receptor status (estrogen and progesterone receptors), HER2 status, menopausal status, stage, and overall health.

Endocrine therapy is a key systemic approach when a tumor is hormone receptor–positive, because these cancers can use estrogen signals to grow. In this setting, endocrine therapy may be used after initial treatment to lower the chance of the cancer returning (adjuvant therapy), or it may be used to control cancer that has come back or spread (advanced or metastatic disease). Letrozole is one of the most commonly discussed options within these breast cancer treatment options when estrogen reduction is the goal.

Hormone therapy for breast cancer: core concepts

Hormone therapy for breast cancer works by interfering with estrogen’s ability to stimulate cancer cells. There are two broad strategies:

One strategy blocks estrogen’s action at the receptor. Tamoxifen is the best-known example; it binds to estrogen receptors and can prevent estrogen-driven signaling in breast tissue.

The other strategy lowers estrogen levels in the body. Aromatase inhibitors (AIs) do this by inhibiting aromatase, an enzyme involved in estrogen production in postmenopausal people. Letrozole is an AI. In premenopausal people, the ovaries produce most estrogen, so AIs are typically used only when ovarian function is also suppressed, based on an oncology team’s assessment.

Because endocrine therapy is often taken for years, benefits and side effects are considered alongside long-term health priorities such as bone strength, heart health, and quality of life. This is also where lifestyle choices, including diet and physical activity, can become meaningful supports (without replacing medical care).

Letrozole for breast cancer: use, timing, diet

Letrozole for breast cancer is commonly prescribed as a once-daily oral tablet, often at 2.5 mg daily, though the exact plan is individualized. In early-stage disease, it may be started after surgery and other indicated treatments, and the planned duration can extend for multiple years depending on recurrence risk and prior therapy.

Taking letrozole at the same time each day can help with adherence. If side effects interfere with routine (for example, morning stiffness), some people discuss timing changes with their clinician. It is important not to stop or adjust dosing on your own, because consistent exposure is part of how endocrine therapy provides protection.

Diet does not replace letrozole, but it can support areas that treatment may strain, particularly bones and cardiovascular health. Practical dietary habits often emphasized during AI therapy include:

• Bone support: Aim for adequate calcium and vitamin D from food and supplements if recommended. Calcium-rich foods include dairy, fortified plant milks, tofu set with calcium, canned salmon with bones, and leafy greens.
• Protein and strength: Adequate protein supports muscle maintenance, especially when joint discomfort reduces activity. Include sources like beans, lentils, fish, poultry, eggs, or dairy.
• Heart-friendly patterns: Favor fiber-rich foods (vegetables, fruits, whole grains) and unsaturated fats (olive oil, nuts, seeds). These habits can complement routine monitoring of cholesterol and blood pressure.
• Alcohol and ultra-processed foods: Limiting alcohol and heavily processed foods may help overall metabolic and heart health; personal guidance should come from your care team.

Breast cancer hormone therapy drugs: what differs

Breast cancer hormone therapy drugs are not interchangeable; they differ in mechanism, side-effect profile, and which patients they are best suited for. Letrozole is one of three commonly used aromatase inhibitors, alongside anastrozole and exemestane. While all reduce estrogen production, individual tolerance can vary.

Tamoxifen is often used in premenopausal patients and can also be used after menopause. Its side effects and risks differ from aromatase inhibitors, and switching between classes may be considered for reasons such as tolerability, menopausal status changes, or specific risk-benefit discussions.

In advanced disease, endocrine therapy may be paired with other medicines (for example, targeted agents) depending on the biology of the cancer and prior treatments. These combinations can change monitoring needs and side-effect expectations. Because supplements and other medications can interact, it is important to share a complete list of prescriptions, over-the-counter drugs, and herbal products (including items like St John’s wort) with the oncology team.

Letrozole side effects in breast cancer patients

Letrozole side effects in breast cancer patients can range from mild to more disruptive, and they often reflect low estrogen levels in the body. Commonly reported effects include hot flashes, night sweats, fatigue, sleep disruption, vaginal dryness, and mood changes. Joint and muscle aches (arthralgia and myalgia) are also frequent and can affect hands, knees, hips, or back.

Two long-term issues often monitored during aromatase inhibitor therapy are bone density loss and changes in blood lipids. Your clinician may recommend baseline and follow-up bone density scans, and in some cases bone-protective medications. Weight-bearing exercise, resistance training, adequate calcium and vitamin D, and fall-prevention habits can also be discussed as part of a bone health plan.

When side effects are significant, it is reasonable to ask about strategies such as symptom-targeted treatments, physical therapy for joint pain, switching to a different aromatase inhibitor, or considering another endocrine option when appropriate. The goal is to maintain effective therapy while protecting daily function and overall health.

In general, seek urgent medical attention for severe symptoms such as chest pain, sudden shortness of breath, fainting, signs of an allergic reaction, or any new symptom that feels dangerous or rapidly worsening.

In summary, letrozole is an important endocrine therapy option for hormone receptor–positive breast cancer, especially after menopause, and it is typically taken daily for a planned period tailored to your situation. Understanding how it works, planning for side effects, and using diet and lifestyle to support bone and heart health can help you navigate treatment more confidently while keeping decisions grounded in guidance from your oncology team.