UPDATE 1-AstraZeneca's Imfinzi combination fails advanced lung cancer study

(Adds details on study, treatment, context on lung cancer)

Aug 21 (Reuters) - AstraZeneca said on Wednesday a combination treatment including its lung cancer drug Imfinzi failed to extend the lives of patients with advanced non-small cell lung cancer (NSCLC) and high levels of gene mutations.

The clinical trial, called NEPTUNE, was testing Imfinzi along with FDA-approved tremelimumab and comparing the combination to platinum-based chemotherapy to treat patients whose cancer had spread to other parts of the body.

London-listed AstraZeneca said though the trial involved a wide range of patients, the primary group being tested had high levels of mutations in their DNA.

The combination treatment did not meet the main goal of improving overall survival in the primary group, the company said.

Mutations in tumours are measured using a system called tumour mutational burden (TMB) and the primary group had TMB of 20 or more.

Imfinzi belongs to the immunotherapy class of treatments that boost the body's own immune system to fight cancer, and tumours with high levels of TMB may be more visible to the immune system.

Rival immunotherapies include Bristol-Myers Squibb's Opdivo.

NSCLC accounts for up to 85% of lung cancers, by far the leading cause of cancer death among men and women, according to the American Cancer Society. (Reporting by Pushkala Aripaka in Bengaluru; Editing by Arun Koyyur and Patrick Graham)