(Reuters) -AstraZeneca's blockbuster cancer drug Imfinzi has failed as a follow-up therapy to improve disease-free survival in a late-stage trial in patients with a type of early-stage lung cancer, the group said on Tuesday.

Imfinzi is a human monoclonal antibody, which works to block a tumour's ability to evade and dampen the immune system, while also boosting the body's anti-cancer immune response, offering an alternative to chemotherapy.

The trial, known as ADJUVANT BR.31 Phase III, sought to evaluate Imfinzi in the adjuvant treatment of 1,415 patients with an early stage of non-small-cell lung cancer following complete tumour removal with or without adjuvant chemotherapy.

An adjuvant therapy is an additional cancer treatment given after the primary treatment to lower the risk of relapse. Disease-free survival is the length of time after treatment that a person lives without the cancer returning.

"We are disappointed in the ADJUVANT BR.31 results," said Susan Galbraith, executive vice president of oncology research and development at AstraZeneca.

Lung cancer is a leading cause of cancer death, and non small-cell lung cancer is the most comment type of the disease. A majority of patients with resectable, or operable, disease eventually develop recurrence despite complete tumour removal and adjuvant chemotherapy, according to the drugmaker.

The latest results were a contrast to the ones published in April, when the Anglo-Swedish drugmaker said Imfinzi had in a separate trial helped improve survival in patients in the early stages of small-cell, or aggressive type, of lung cancer, meeting two key trial goals.

The ADJUVANT BR.31 Phase III study is a randomised, double-blinded trial sponsored by the Canadian Cancer Trials Group and conducted across Canada, the U.S., Australia, Europe and Asia.

Imfinzi made $4.24 billion in sales last year. The U.S. Food and Drug Administration first approved the drug in 2017 to treat a type of bladder cancer.

It won approval for use in mid-stage non-small cell lung cancer a year later and in March 2020, the FDA approved Imfinzi to target extensive-stage small-cell lung cancer.

(Reporting by Yadarisa Shabong in Bengaluru; Editing by Sherry Jacob-Phillips and Jan Harvey)