The drug, developed by AstraZeneca, if taken daily after surgery, dramatically reduces risk of death, according to a new study.

Taking the drug osimertinib, which is marketed under the name Tagrisso, dramatically reduced the risk of death by 51 percent in patients whose tumours were removed surgically, according to the results presented at an American Society of Clinical Oncology (ASCO) meeting on Sunday.

Lung cancer is the form of the disease that causes the most deaths, with approximately 1.8 million fatalities every year worldwide.

The treatment developed by the pharmaceutical group AstraZeneca targets a particular type of lung cancer in patients suffering from so-called non-small cell cancer, the most common type, and showing a particular type of mutation.

These mutations, on what is called the epidermal growth factor receptor (EGFR), affect 10 percent to 25 percent of lung cancer patients in the United States and Europe, and 30 to 40 percent in Asia.

The clinical trial included some 680 participants at an early stage of the disease, in more than 20 countries. They had to have been operated on first to remove the tumour, then half of the patients took the treatment daily, and the other half a placebo.

The result showed that taking the tablet resulted in a 51 percent reduction in the risk of death for treated patients compared with the placebo.

After five years, 88 percent of patients who took the treatment were still alive, compared with 78 percent of patients who took the placebo.

These data are “impressive”, said Roy Herbst of Yale University, who presented them in Chicago. The drug helps “prevent the cancer from spreading to the brain, to the liver, to the bones”, he added at a news conference.

About a third of cases of non-small cell cancers can be operated on when detected, he said.

“This is a pretty dramatic and remarkable improvement,” said Dave Fredrickson, executive vice president of oncology at AstraZeneca in an interview with Reuters news agency.

“It is hard for me to convey, I think, how important this finding is,” said Nathan Pennell of the Cleveland Clinic Foundation at the news conference.

“We started entering the personalised therapy era for early-stage patients,” said Pennell, who did not take part in the trials, and noted that “we should firmly close the door on one-size-fits-all treatment for people with non-small cell lung cancer.”

Osimertinib is already authorised in dozens of countries for various indications, and has already been given to some 700,000 people, according to a press release from AstraZeneca.

Its approval in the US for early stages in 2020 was based on previous data that showed an improvement in patient disease-free survival, that is, the time a patient lives without a recurrence of cancer.

But not all doctors have adopted the treatment, and many were waiting for the data on overall survival that was presented on Sunday, said Herbst.

He stressed the need to screen patients to find out if they have the EGFR mutation. Otherwise, he said, “we cannot use this new treatment”.

Osimertinib, which targets the receptor, causes side effects that include severe fatigue, skin rashes or diarrhoea.