Treatment with Novartis AG's (NVS) Femara can halve the risk of breast cancer returning even when started one to seven years after finishing standard therapy, new data released Monday showed.
Results of the study, which involved women originally in the placebo arm of an international trial of Femara, generically known as Letrozole, will appear in the Journal of Clinical Oncology and are receiving early online release.
Among those women who chose to start Femara treatment after the initial trial stopped, the risk their cancer would return was only 2%, compared with almost 5% in those choosing no treatment, the study's authors said.
The risk of the cancer spreading to other parts of the body was 61% lower with Femara, while the risk that a new tumor would develop in the unaffected breast dropped more than 80%, the researchers said.
Femara belongs to a class of drugs called aromatase inhibitors which suppress the production of estrogen, which fuels many breast cancer tumors. Astra Zeneca PLC's (AZN) Arimidex and Pfizer Inc.'s (PFE) Aromasin belong to the same class. The most widely used estrogen-blocking drug is Tamoxifen, the standard treatment which has been used for more than 25 years. But after five years, treatment with Tamoxifen is stopped because it appears to provide no additional benefit while its side effects continue.
Sales of Femara rose 30% in 2007 to $937 million. Arimidex sales rose 15% to $1.73 billion, while those of Aromasin increased 25% to $401 million.
The original MA-17 trial, which involved 5,000 post-menopausal women, was stopped a year early in 2003, after Femara was found to lower the risk of the cancer returning by 43%.
Since women who received Femara in this trial began taking the drug within a few months of stopping Tamoxifen treatment, the drug's current approval restricts the start of therapy to the first three months after stopping treatment with Tamoxifen. The results of the new trial will allow Novartis to file for approval to sell the drug to women who stopped standard therapy as much as seven years ago.
Participants in the placebo arm of the MA-17 trial were offered the opportunity to begin Femara treatment when that trial was halted, which gave investigators the opportunity to determine whether those women could also benefit from the drug.
The current study analyzes data on more than 1,500 women from the placebo group who chose to take Femara and about 800 who chose no further treatment.
The study was supported by grants from the Canadian Cancer Society, the National Cancer Institute of Canada and the U.S. National Cancer Institute.
Novartis also supported it and provided study medications, as it did for the initial trial.