Oct 18 (Reuters) - Pfizer ( PFE ) and Japanese firm

Astellas' drug Padcev, combined with Merck's ( MRK )

Keytruda, lowered the risk of tumor recurrence, progression or

death in patients suffering from a type of bladder cancer, the

companies said on Saturday.

The late-stage trial studied patients with muscle-invasive

bladder cancer (MIBC) who were ineligible for or declined

chemotherapy with the commonly used cancer drug, cisplatin, and

were given the combination before and after surgery.

The combination therapy showed improvement in event-free

survival - which measures how long a patient remains free from

disease recurrence and other complications - with a 60%

reduction in the risk of tumor recurrence, progression or death

for patients compared to surgery alone. It also improved overall

survival, with a 50% reduction in the risk of death.

The ability of the combination to reduce the risk of death

by half in this setting was a remarkable advancement for

patients who have limited treatment options and often face poor

prognoses, said Pfizer's ( PFE ) Chief Oncology Officer Jeff Legos.

An estimated 74.7% of patients treated with the combination

were event-free at two years, compared to 39.4% who received

surgery only, the companies said.

Bladder cancer is the ninth most common cancer worldwide.

MIBC, which represents 30% of all bladder cancers, is a type of

cancer that grows into the muscle layer of the bladder wall.

Merck's ( MRK ) top-selling drug Keytruda helps the body's own

immune system fend off cancer by blocking a protein called PD-1,

while Padcev, an antibody-drug conjugate, targets specific

cancer cells without damaging healthy ones.

The combination is not currently approved to be given before

and after surgery in cisplatin-ineligible patients with MIBC.

The companies said the results would be discussed with

global health authorities for potential regulatory filings.