According to the Canadian Cancer Society more than 21,000 women will be diagnosed with breast cancer every year and more than 5,000 will die. (U.S. figures are more than 10 times those in Canada.) Surgery is generally considered the first method of treatment. However, many women suffer recurrences of cancer. For this reason many women are treated with Tamoxifen. But after 5 years, tumors develop a resistance to Tamoxifen. A new drug called Letrozole was developed by Novartis Pharmaceuticals to replace Tamoxifen. To determine its effectiveness, a study involving 5,187 breast cancer survivors from Canada, the United States, and Europe was undertaken. Half the sample received Letrozole and the other half a placebo. The study was to run for 5 years. However, after only 2.5 years it was determined that 132 women receiving the placebo and 75 taking the drug had recurrences of their cancers. The study was published in the New England Journal of Medicine.

Do these results provide sufficient evidence to infer that Letrozole works?