New treatments reduce the risk and recurrence of breast cancer in postmenopausal women

The first trial has shown that in postmenopausal women who are at increased risk of developing breast cancer, the drug exemestane reduces this risk by 65 percent compared with placebo.

“The 65 percent reduction in breast cancers was what we expected to see,” says Harriet Richardson, an assistant professor in Queen’s Department of Community Health and Epidemiology and Project Coordinator at NCIC CTG. “Women on exemestane experienced fewer tumours and exemestane was found to be both safe and tolerable with no significant worsening in overall quality of life.”

Exemestane is shown to prevent breast cancer without the serious toxicities of other preventative drugs, such as tamoxifen. This reduced toxicity is due to the way exemestane counteracts estrogen, a hormone commonly implicated in causing breast cancer.

Results from the second clinical trial indicate radiation treatment to lymph nodes in the region of the breast, in addition to treating the main tumour, improves breast cancer patient survival rates and reduces cancer recurrences near the original tumour site and in other parts of the body.

An interim analysis of the data conducted in March 2011 found that after a median follow up of 62 months, there were statistically significant benefits for the group of women receiving the added region node irradiation (RNI) therapy. These included a greater than 30 percent improvement in disease free survival (from 84 percent for those who received whole breast irradiation to 89.7 percent for those who also got RNI at 5 years), as a result of a 41 percent lower rate of recurrences near the tumour site (from 5.5 percent to 3.2 percent at 5 years), and a 36 percent lower rate of cancer recurrences in other parts of the body (from 13 percent to 7.6 percent at 5 years).

“These significant and promising results will encourage physicians to offer all women with breast cancer that has spread to the lymph nodes the option of receiving irradiation to the regional lymph nodes,” says Wendy Parulekar, an associate professor of oncology at Queen’s, medical oncologist at Kingston General Hospital, and Physician Coordinator at NCIC CTG.

These findings were presented today at the American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago. The results of the exemestane trial have been accepted for publication in the New England Journal of Medicine.

These trials were led and conducted by the NCIC Clinical Trials Group (NCIC CTG), a cancer clinical trials cooperative group that conducts trials testing anti-cancer and supportive therapies across Canada and internationally. The NCIC CTG’s Central Office is located at Queen’s University in Kingston, Ontario, Canada.

The NCIC CTG receives programmatic funding, including funding for its prevention initiative, from the Canadian Cancer Society Research Institute. Additional support for the NCIC CTG prevention initiative was provided by the Canadian Institutes for Health Research. The prevention trial was supported with funds provided by Pfizer. The regional irradiation trial was also supported by the US National Cancer Institute / Cancer Therapy Evaluation Program and with funds provided by the Canadian Breast Cancer Research Alliance.