Anastrozole Confirmed Superior in Breast Cancer Prevention

SAN ANTONIO, Dec. 14 /PRNewswire/ -- Anastrozole is more effective than
tamoxifen at preventing breast cancer recurrence for periods of at least 10
years in women with hormone-responsive cancers. In addition, the increased
risk of fractures that has been seen in some patients being treated with
anastrozole disappears after treatment ends.
Speaking at the Thursday session of the San Antonio Breast Cancer
Symposium, Professor John Forbes of the University of Newcastle presented the
much-anticipated long-term results of the ATAC (Anastrozole, Tamoxifen, Alone
or in Combination) trial that compared 5 years of tamoxifen with 5 years of
the aromatase inhibitor anastrozole for the treatment of postmenopausal women
with invasive breast cancer.
Hormone-responsive breast cancers require estrogen stimulation in order to
grow. Tamoxifen, a synthetic variation of estrogen, binds to hormone receptors
on hormone-sensitive cancer cells, preventing estrogen from attaching to the
cells. Anastrozole, on the other hand, prevents the manufacture of estrogen by
body tissues other than the ovaries (e.g., fat cells), so it is useful for the
treatment of hormone-sensitive cancers in postmenopausal women whose ovaries
are no longer producing estrogen.
Although previous reports at 33 and 68 months demonstrated that
anastrozole was more effective, has fewer serious side effects, and was better
tolerated than tamoxifen during the period of treatment, it was not known
whether the benefits or side effects associated with anastrozole would persist
long term after patients were no longer taking the drug.
After 10 years (5 years after the completion of treatment), patients who
had taken anastrozole continued to show reduced rates of tumor recurrence and
metastasis compared with patients who had taken tamoxifen. In fact, the
relative benefit of anastrozole actually increased compared with results seen
immediately after the completion of treatment.
Most strikingly, the incidence of a new cancer occurring in the other
breast was significantly lower at 10 years in women who took anastrozole
compared with those who received tamoxifen. Tamoxifen has been approved for
several years for use in preventing new breast cancers, and it now appears
that anastrozole may be even more effective.
Many patients have been reluctant to begin treatment with anastrozole
because of concern about the potential for increased bone loss and risk of
fracture that can occur with the use of aromatase inhibitors. It was not known
whether these effects would persist after the end of treatment. With the new
data presented today, it appears that they do not. Although the incidence of
fractures was nearly 30% higher in patients treated with anastrozole while
they were taking the drug, that difference disappeared after treatment was
completed. In addition, there do not appear to be any other important side
effects related to anastrozole treatment at this time.
SOURCE San Antonio Breast Cancer Symposium

San Antonio Breast Cancer Symposium, +1-210-582-7004