AstraZeneca's pill Tagrisso cut the risk of lung cancer progressing by 70 percent compared to standard chemotherapy in a major clinical trial, lifting prospects for a drug that is key to the company's ambitious long-term sales goals.

The medicine is designed to help cancer patients with certain genetic mutations that are very common in China and other parts of east Asia.

Tagrisso is already on the market, winning early approval based on mid-stage studies and selling $276 million in the first nine months of 2016, but AstraZeneca was required to produce a confirmatory Phase III randomised study detailing its benefits.

Results published on Tuesday in the New England Journal of Medicine showed that Tagrisso, given as a second-line treatment, helped patients live a median 10.1 months before their cancer worsened, against 4.4 months for those on chemotherapy.