A new type of drug shows growing promise as a more potent way for many breast cancer patients to significantly cut their risk of a recurrence, researchers reported yesterday.
The latest findings from a large international study also found that the drug, called an aromatase inhibitor, appears to sharply reduce the chances that many breast cancer patients will develop a new cancer in the other breast or have the cancer spread elsewhere.
The results were so strong that the researchers recommended that most postmenopausal women struck by breast cancer should immediately begin taking an aromatase inhibitor as soon as they are done with the standard regimen of surgery, radiation and, often, chemotherapy, instead of first going on an older drug.
Other experts praised the findings as confirming that aromatase inhibitors should play an important role in treating breast cancer patients, but they said it remains unclear whether all eligible women should immediately start with an aromatase inhibitor. Some patients might still first try the older drug, tamoxifen, they said.
"This is a very large study, and it confirms there is a benefit and that aromatase inhibitors should become part of standard therapy," said JoAnne Zujewski of the National Cancer Institute. "But the exact timing of how one should use them remains unclear."
Before the development of aromatase inhibitors, women whose breast cancers were promoted by the hormone estrogen -- which is true of most -- were given tamoxifen to reduce their risk of a recurrence. Tamoxifen blunts estrogen's effects. But tamoxifen can be taken for only five years, and it increases the risk of blood clots, which can cause strokes, and uterine cancer.
Aromatase inhibitors block the formation of estrogen in the first place and carry none of those risks. They do not, however, reduce the risk of osteoporosis, as tamoxifen does.
It has been unclear whether women should take tamoxifen first and then switch to an aromatase inhibitor, or simply take an aromatase inhibitor from the start.
The new findings are from a study involving 9,366 postmenopausal women with early, estrogen-sensitive breast cancer who took either tamoxifen or an aromatase inhibitor called Arimidex (known generically as anastrozole).
The researchers had previously reported data from three years of study that showed Arimidex prevented more recurrences than tamoxifen. The new data showed that the benefits continued after five years and appeared to be even greater, the researchers said. Tamoxifen cut the recurrence risk by about 50 percent; Arimidex appeared to reduce the recurrence rate by an extra 26 percent, the researchers said.