Letrozole is an oral medication primarily known as an aromatase inhibitor. It is prescribed for specific health conditions, offering targeted therapeutic effects.
Understanding Letrozole’s Role
Letrozole functions by inhibiting the enzyme aromatase, which is responsible for converting androgens into estrogens in the body. By blocking this conversion, letrozole effectively reduces estrogen levels. This mechanism of action is central to its applications in treating certain types of breast cancer and in fertility treatments.
In postmenopausal women, aromatase is the primary source of estrogen production in tissues like fat, muscle, and skin. Reducing estrogen levels can hinder the growth of hormone-sensitive breast cancers that rely on estrogen for proliferation. For fertility, the reduction in estrogen prompts the body to increase follicle-stimulating hormone (FSH), which can induce or enhance ovulation.
Starting Letrozole for Fertility
When letrozole is used for fertility treatment, particularly for ovulation induction, the timing of its administration is precisely aligned with the menstrual cycle. Healthcare providers typically advise starting letrozole tablets on specific days, commonly from day 2, 3, 4, or 5 of the menstrual cycle, and continuing for five consecutive days. Day one is designated as the first day of menstrual bleeding. The usual starting dose for ovulation induction is 2.5 mg once daily.
This timing is critical because it encourages the pituitary gland to release more FSH. Increased FSH stimulates the ovaries to develop mature follicles, which are sacs containing eggs. This promotes the growth of a dominant follicle, leading to ovulation.
Following the five-day course, monitoring tracks follicle development and predicts ovulation. This typically involves transvaginal ultrasound scans around day 10 to 12 of the cycle to measure follicle size and endometrial lining thickness. Blood tests, such as progesterone levels, may also confirm ovulation about a week after it’s expected.
Ovulation usually occurs approximately 7 to 10 days after starting the medication, or between days 14 and 19 of the cycle if treatment began on day 3. Patients are often advised to engage in timed intercourse around this predicted ovulation window to maximize the chances of conception. If ovulation occurs but pregnancy does not, the same letrozole dose may continue for up to six cycles. If a patient does not respond, the dose may be increased in 2.5 mg increments up to 7.5 mg.
Starting Letrozole for Breast Cancer
Letrozole is frequently prescribed for hormone-sensitive breast cancer, primarily in postmenopausal women. Its use extends to various stages of the disease, including early, advanced, and as extended adjuvant therapy after treatments like tamoxifen. The initiation of letrozole in this context is generally not tied to a menstrual cycle, as it is in fertility treatment.
For breast cancer, letrozole is typically taken as a continuous daily medication, usually a 2.5 mg tablet once a day. It can be taken with or without food, but maintaining a consistent daily schedule is recommended. This consistent dosing continuously suppresses estrogen production, inhibiting the growth of hormone-receptor-positive cancer cells.
Letrozole may be used as an adjuvant therapy following surgery to reduce the risk of cancer recurrence. In some cases, it can be prescribed as a neoadjuvant therapy before surgery to shrink larger tumors. For advanced or metastatic breast cancer, letrozole may be continued as long as it effectively controls the disease. The duration of treatment for early breast cancer can range from five to ten years.
Key Considerations During Treatment
Consistent adherence to the prescribed letrozole regimen is important for treatment effectiveness. Taking the medication at the same time each day helps maintain consistent drug levels and improves adherence. If a dose is missed, patients are generally advised to take it as soon as remembered, unless it is almost time for the next scheduled dose, in which case the missed dose should be skipped to avoid taking a double dose.
Ongoing communication and monitoring with a healthcare provider are integral throughout letrozole treatment. Regular check-ups, including blood tests and imaging, help assess effectiveness and overall health. For fertility treatment, monitoring follicle growth and confirming ovulation are standard practices. In breast cancer treatment, monitoring involves assessing tumor response and managing any potential long-term effects.