Letrozole (FEMARA)

Breast cancer, early stage

Breast cancer, advanced or metastatic

Breast cancer, early stage

• Dose – Oral: 2.5 mg once daily continuously for up to 5-10 years
• Given as monotherapy or in combination with abemaciclib
• Patients can also be switched from tamoxifen to letrozole for a total duration of 5-10 years of treatment

Breast cancer, advanced or metastatic

• Dose – Oral: 2.5 mg once daily continuously until disease progression or unacceptable toxicity
• Given as monotherapy or in combination with palbociclib or ribociclib

Available as 2.5 mg tablets. Tablets contain lactose and tartrazine. Tablets should NOT be broken or crushed. Store at room temperature.

Aromatase Inhibitor

Take with or without food

If a dose is missed, patients should be instructed to take it as soon as they remember, unless it is close to the next dose. If it is close to the next dose, patients should skip the missed dose and resume with the next scheduled dose.

Common: Hot flashes, Arthralgia/myalgia.

Less Common: Peripheral edema, Nausea, Hypercholesterolemia, Fractures, Osteoporosis, Headache, Vaginal dryness.

The adverse effects listed above are not exhaustive. Please refer to the relevant product monograph for full details.

Baseline before treatment: Bone density before or after 2 to 3 month trial of therapy.

During treatment: Bone density (follow up every 3 years or as clinically indicated).

If clinically indicated: serum cholesterol, triglycerides.

• Avoid estrogen-containing or estrogenic agents if possible as they can decrease the effect of letrozole.
• This drug can impact or be impacted by metabolic enzymes for absorption and excretion. Many drugs can also affect or be affected by these enzymes, so please consult with pharmacy to assess for interactions.
• Current drug interaction databases should be consulted for more information.

• Avoid in pregnancy and lactation.
• Arthralgia, joint stiffness, and/or ostealgia, may occur with letrozole. Pain can be managed with over-the-counter analgesics, discuss with pharmacy.
• Letrozole is associated with a decreased bone mineral density (BMD).
• If estrogen use is required for patient, the lowest dose and shortest duration to relieve symptoms should be prescribed, and patient should be monitored carefully. For vaginal complaints such as dyspareunia, dryness and sexual dysfunction, topical estrogen may be considered.

BC Cancer. BC Cancer Drug Manual. Letrozole. Vancouver, British Columbia: BC Cancer Agency. Available at: http://www.bccancer.bc.ca/drug-database-site/Drug%20Index/Letrozole_monograph_1April2011.pdf. Updated April 1, 2011. Accessed January 22, 2024.

Lexicomp. Exemestane Monograph. In: Lexi-Drugs. Hudson, Ohio: Lexi-Comp, Inc. Available at: https://online.lexi.com/lco/action/doc/retrieve/docid/patch_f/7157?cesid=2e2ZITgkTVb&searchUrl=%2Flco%2Faction%2Fsearch%3Fq%3Dletrozole%26t%3Dname%26acs%3Dtrue%26acq%3Dmetros. Updated January 29, 2024. Accessed January 30, 2024.

Cancer Care Ontario. Letrozole  Monograph. Drug Formulary. Toronto, Ontario: Cancer Care Ontario. Available at: https://www.cancercareontario.ca/en/drugformulary/drugs/monograph/43956. Updated November 2020. Accessed January 22, 2024.

Novartis Pharmaceuticals Canada Inc. Femara Product Monograph. Updated July 27, 2023.