(Corrects stock symbol to AZN.L from AZL.N in paragraph 8)
By Julie Steenhuysen
CHICAGO, Dec 14 (Reuters) - Women who took AstraZeneca Plc’s breast cancer drug Arimidex fared better than those who took the pill tamoxifen even four years after they stopped taking it, researchers said on Friday.
Arimidex belongs to a new class of breast cancer drugs known as aromatase inhibitors, which block the production of estrogen that can lead to cancer.
“We did not have any data on what would happen to these patients who were being offered the therapy once therapy stopped — whether they would would remain alive and free of cancer,” said Dr. Aman Buzdar of the University of Texas M.D. Anderson Cancer Center in Houston, who led the U.S. portion of the trial.
The global trial was funded by AstraZeneca in collaboration with academic research centers.
The study, which offers a little more than eight years of follow-up data — the longest yet — was published online in the Lancet Oncology medical journal to coincide with its presentation at San Antonio Breast Cancer Symposium.
It suggests treatment benefits extend long after active treatment has ended.
“The data confirm that we are keeping more patients alive without the recurrence of cancer,” said Buzdar in a telephone interview from the symposium.
Tamoxifen transformed breast cancer therapy when it was shown to reduce the risk of cancer coming back by close to 50 percent. But the pill, sold by AstraZeneca (AZN.L) under the brand Nolvadex and also sold generically, raises the risk of death from strokes and endometrial cancer.
Dr. John Forbes of the University of Newcastle in New South Wales, Australia, led a team that compared the use of Arimidex, known generically as anastrozole, with tamoxifen in more than 9,000 post-menopausal women with hormone-sensitive early breast cancer that had not spread to other parts of the body.
Earlier results showed that at 5-1/2 years (68 months) of follow up, women treated with Arimidex fared better with significantly fewer side effects than those treated with tamoxifen. One exception is that women on Arimidex did have more bone fractures.
In the latest study, Arimidex continued to keep breast cancer at bay some four years after treatment ended, with fewer women having a recurrence of breast cancer compared with the tamoxifen group.
The study found no significant difference in the risk of heart-related deaths between women treated with Arimidex or tamoxifen. And the increased risk of fractures seen in Arimidex patients did not persist after treatment ended.
“These drugs are definitely superior to tamoxifen. They keep more patients free of cancer and they have a better safety profile compared to tamoxifen,” Buzdar said.
The study found no difference in overall survival between the two groups, a finding they said is likely because the average age of the patients was 72 and many of the women died from causes other than breast cancer.
Breast cancer is the second-leading cause of cancer death among U.S. women, after lung cancer. It kills 500,000 people globally every year.
Pfizer Inc (PFE.N) also makes an aromatase inhibitor called exemestane, which it sells under the brand name Atomasin.