Aided by a better understanding of breast cancer biology, treatments for primary and metastatic breast cancers have achieved significant advances in recent years, said the Breast Cancer Society of Taiwan, which is holding the “2013 Taipei International Breast Cancer Symposium” this weekend, with the attendance of Hematology-Oncology head Dennis Slamon, whose research has led to the development of a new targeted breast cancer treatment, which may improve treatment for about 25 percent of the breast cancer patients who have a specific genetic alteration.
Slamon discovered that women suffering from cancers with an over-expression of HER 2 protein in tumors are at a higher risk of cancer recurrence and distant metastasis.
The subsequent discovery of the antibodies against HER2, accompanied by a series of clinical trials, resulted in a targeted therapy for HER 2 positive breast cancer patients, which reduces the rate of breast cancer recurrence by 50 percent, according to the society.
“And the HER 2 positive breast cancer population has gone from having the worst outcome among the breast cancers to now having the best outcome,” Slamon said.
Knowing whether the breast cancer is sensitive to hormones — hormone receptor (HR) positive or negative — and the level of human epidermal growth factor receptor 2 (HER2) helps determine what is the best treatment for the patient. All HR-positive breast cancers are to receive hormone therapy and the HER-2 positive breast cancer are to receive targeted therapy, chairman of the society Huang Chiun-Sheng (黃俊升) said.
As the binding of hormone estrogen receptor (ER) and estrogen can induce the growth of cancer cells and thus cancer recurrence after surgery, two approaches have been adopted to “downmodulate the estrogen activity,” Huang said. Anti-estrogens, such as tamoxifen, act as ER antagonists that can “inhibit the ER’s ability to bind estrogen,” and aromatase inhibitors (AI) can prevent the synthesis of estrogen.
About 60 percent to 66 percent of the breast cancer patients have HR-positive breast cancer, secretary general of BCST Tseng Ling-ming (曾令民) said.
“In recent years there have been promising advances in the treatment. It has been shown by studies that for postmenopausal women with HR positive early-stage breast cancer, five years of initial therapy with AI can better reduce the risk of recurrence and increase the survival than tamoxifen,” Tseng said.
“Also, a 10-year hormone therapy has also been shown to result in better patient outcome than a five-year one for women with HR positive cancers, who are at higher risk of recurrence five years after surgery [compared with those with HR negative cancers].”
“The third advance is the introduction of mTOR inhibitors for people with locally advanced or fourth-stage HR positive breast cancer, who have become resistant to hormone therapy and would have to resort to chemotherapy, which would compromise the quality of life for the patient,” Tseng added. “Using mTOR in combination with AI has been shown to be able to overcome resistance and achieve improvement in progression-free survival.”