medical update

The Latest Advances in Adjuvant Therapy
Dr. Susan Ellard
Chair, Breast Systemic, BC Cancer Agency

In July 2005, the Breast Tumour Group initiated two new treatment policies, aimed at improving the survival of women diagnosed with early stage breast cancer. The first concerned new treatment approaches for postmenopausal women with estrogen receptor positive tumours. For some of these women, an aromatase inhibitor (anastrazole, letrozole, exemestane) was recommended to prevent cancer relapse.

The second new policy concerned women with over-expressed her2/neu breast cancer. For these individuals, a drug called trastuzumab, also known Herceptin® was suggested for one year, in addition to regular chemotherapy.

A variety of large international trials have now examined the use of drugs called aromatase inhibitors (AIs) as a therapy for early stage breast cancer. Trials have examined the use of these drugs compared to 5 years of tamoxifen; or after 2-3 years of tamoxifen, compared to 5 years of tamoxifen; or after 5 years of tamoxifen, compared to no further treatment.

What has been shown is some degree of advantage administering aromatase inhibitors over just tamoxifen, to reduce relapses. Currently, only one trial has shown these new drugs improve survival, compared to just tamoxifen and its primarily in patients with higher risk, node-positive cancers. Its expected that, with long-term follow-up, other studies may also show an increase in breast-cancer survival, as fewer relapses occur. Currently, there are no trials, able to compare aromatase inhibitors from the onset, to using them after a period of tamoxifen.

Since the trials, the Breast Tumour Group is recommending that most post-menopausal women with estrogen receptor positive tumours, receive an initial course of tamoxifen for about 2 ½-years and then have aromatase inhibitors for 2 ½ years. For women who may be at higher risk of relapse within the first 2 ½ years of treatment, an AI can be considered as initial therapy and continued for 5 years in total. High risk tumours would be larger sized or have extensive lymph node involvement or higher grade of cancer cells.

For women who are pre-menopausal when diagnosed with breast cancer, if menopause occurs during tamoxifen therapy, a switch to an aromatase inhibitor can be offered after about 2 ½-years or after 5 years. If used after 5 years, the current recommendation is to continue an AI for three additional years. Women who have low risk tumours (less than 2 centimetres with no lymph node or lymphatic invasion and with low-grade) would continue to receive only tamoxifen for 5 years, because evaluation of patients treated in BC has shown an excellent chance for a cure, without additional therapy.
The side effects of aromatase inhibitors are very similar to tamoxifen, but the risks are slightly different. These would include menopausal symptoms such as hot flashes, vaginal dryness or discharge and sometimes moodiness, short term headaches or nausea. About a third of patients have aching muscles or joints but usually to tolerable levels.

The main risk of AI-therapy is the depletion of estrogen causing bone thinning or osteoporosis. This can increase the risk of fractures; therefore, these drugs might not be ideal for patients with other significant risks for osteoporosis. The other lesser risk is that lipid levels, such as cholesterol, might be raised. Someone with already present lipid problems should be carefully monitored when they start AIs. When it comes to uterine cancer or blood clots, aromatase inhibitors do not create elevated risk like tamoxifen.

The treatment policy using Herceptin is directed at the 15% of women whose breast cancers are her2/neu positive. Women who are her2/neu positive would ordinarily face a higher risk for breast cancer relapse after chemotherapy and other treatments. Three large, international trials have shown that the addition of Herceptin to chemotherapy can reduce the risk of breast cancer relapse in the affected group by about 50%. In one trial, with the longest follow-up, there was a finding of improved survival with Herceptin. Since these findings, the Breast Tumour Group has obtained additional funding to offer this therapy to patients who are her2/neu positive and receiving chemotherapy, or to patients who have completed chemotherapy since July, 2004.

For patients newly diagnosed with her2/neu positive breast cancer, its recommended that Herceptin be added to chemotherapy treatments, usually in the second 3 months in combination with paclitaxel or docetaxel, and then continued after chemotherapy for one-year. With Herceptin there have been some allergic reactions, but these seem to diminish after the first treatment. Theres also a remote possibility of heart failure, so heart function should be tested before and during treatment. For patients who finished their chemotherapy since July of 2004, Herceptin is being recommended for 1 year. Unfortunately, at this time there are no trials using Herceptin for less than 1 year and results are awaited on a trial using Herceptin for 1 versus 2 years. There's also no evidence that Herceptin can be substituted for chemotherapy, so it is being recommended only to patients who will also receive chemotherapy.

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