(Corrects spelling of executive's last name, paragraph 4)
FRANKFURT, Sept 9 (Reuters) - AstraZeneca's cancer treatment Imfinzi has been shown to prolong survival in a particularly aggressive type of lung cancer by close to three months, as the British drugmaker holds its ground in a crowded field against rival immunotherapy drugs.
Imfinzi, when combined with chemotherapy, resulted in a median 13 months survival in a late-stage small cell lung cancer trial, the British drugmaker said on Monday, adding trial details to a brief statement published in June.
Patients in a reference group on chemotherapy only lived a median 10.3 months in the so-called Caspian trial, it said.
"There is a wide recognition that in small cell lung cancer there is very much a need for new therapies," said Dave Fredrickson, head of the company's oncology business.
"There is a clear imperative that chemotherapy alone is not delivering the outcomes that we desire for patients because the disease is so aggressive."
AstraZeneca has already carved out a niche for Imfinzi, which enables the immune system to detect and attack certain cancer cells, in the more common non-small cell lung cancer (NSCLC) setting, with approval for tumours that have only spread in the chest.
Merck & Co's immunotherapy bestseller Keytruda has become the standard treatment option for the larger group of NSCLC patients that are diagnosed at a more advanced stage of the disease.
In the small cell type of cancer, Astra is seeking to catch up with Roche, whose immunotherapy Tecentriq won U.S. approval for the disease type in March.
After 18 months, a third of the patients on Imfinzi and chemotherapy were alive, compared with only about one quarter in the comparable group on chemotherapy only, AstraZeneca said.
Imfinzi generated $633 million in sales last year. (Reporting by Ludwig Burger; Editing by Jan Harvey)