A breast cancer drug made by Pfizer Inc. increased survival rates by 63 percent compared with the standard therapy tamoxifen, researchers said on Wednesday.
The clinical trial strengthens the case for administering the newer drug, exemestane, as a first option. A study published last week showed that women recovering from breast cancer lowered their chance of developing another tumor by 32 percent if they switched to exemestane after two or three years of tamoxifen treatment.
According to the research presented this week at a breast cancer conference in Hamburg, Germany, the median survival for patients taking exemestane was 10.9 months, compared with 6.7 months for patients on tamoxifen. Pfizer provided financial support for the 382-patient study.
"These are very substantive results," said Dr. Robert Paridaens, a lead investigator in the study who began trying the drug in patients in 1989, well before it was approved. "The comparisons are significant."
Pfizer markets exemestane under the brand name Aromasin. The drug was launched in 2000 by Pharmacia, which Pfizer acquired last year, and is not one of Pfizer's top sellers.
Tamoxifen is sold under the brand name Nolvadex by AstraZeneca Plc (London:AZN.L - News) and is usually taken for five years. Sales of Nolvadex totaled $178 million in 2003, down 66 percent from 2002 as it faced cheaper generic competitors.
Tamoxifen works by blocking the hormone estrogen, which can stimulate and feed the growth of breast cancer.
By contrast, exemestane was the first approved oral therapy that binds to an enzyme known as aromatase, which normally converts the hormone androgen into estrogen in postmenopausal women.
The Pfizer drug thereby curtails the actual supply of estrogen to the cancerous tumors that are dependent on it, rather than blocking estrogen after it is already produced.