In Canada, women diagnosed with breast cancer are typically treated first with surgery, chemotherapy, or radiation to eliminate the initial cancer. If the tumour is sensitive to female sex hormones, a medication called tamoxifen is used for five years of adjuvant treatment, a secondary treatment, to prevent the cancer from recurring or spreading to other parts of the body.
But until now, the existing options beyond that - or, more accurately, the lack of options - have made for a Catch-22 of sorts: More than half of all breast cancer recurrences occur after five years, while studies have shown that the benefits of tamoxifen beyond that time don't exceed the risks.
Letrozole, sold under the brand name Femara®, is the first medication approved for extended adjuvant treatment so women may now be able to reduce the threat of recurrence beyond those first five years. Dr. Kathleen Pritchard of the University of Toronto Faculty of Medicine calls it "a treatment option where none existed before."
Letrozole is the second drug in a relatively new class of medications called aromatase inhibitors. These medications lower estrogen levels by blocking a substance called aromatase, which in turn reduces levels of the hormone estrogen, inhibiting the growth of some types of breast cancer. In contrast, tamoxifen blocks estrogen receptors on breast cancer cells, intercepting the hormone's ability to signal a tumour to grow faster.
Health Canada's decision to approve letrozole to extend the period of protection came after a study compared its use after the standard five years of tamoxifen to a placebo (a "sugar pill"). Some 5,187 postmenopausal women who had completed five years of tamoxifen treatment participated in the study, which was published in the New England Journal of Medicine.
At a median follow-up point of 28 months, 132 of the women in the placebo group had had a recurrence of the cancer, compared to just 75 in the letrozole group. Furthermore, 42 women in the placebo group died, compared to 31 in the letrozole group. In fact, an independent panel found these interim results to be so convincing that it recommended that the researchers make letrozole available to the placebo group.
In Canada, an estimated 21,200 women are diagnosed with breast cancer annually, and 5,200 will die from it. While mortality rates from breast cancer are at their lowest since 1950, Barbara Bone of the Breast Cancer Society of Canada describes the five-year mark as a time of "great anxiety" for survivors due to the lack of options that existed before letrozole was approved.
Breast cancer survivor Colleen Montgomery agrees. "There is so much uncertainty when you are living with breast cancer," she said in a press release issued by Femara's manufacturer, Novartis Canada. "You know that the risk of recurrence is always there, but previously you only had five years of treatment."
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