Aug 12 (Reuters) - Pfizer ( PFE ) said on Tuesday its

cancer drug Padcev, in combination with Merck's ( MRK )

Keytruda, significantly improved survival rates in patients with

muscle-invasive bladder cancer when administered before and

after surgery.

The interim results from an ongoing late-stage trial of the

combination therapy showed significant improvement in event-free

survival - which measures how long a patient remains free from

disease recurrence - and overall survival when compared to

surgery alone, the company said.

"These latest results underscore the practice-changing

potential of this combination in earlier stages of bladder

cancer, where it has the potential to improve outcomes for even

more patients," said Johanna Bendell, Pfizer's ( PFE ) oncology chief

development officer.

In muscle-invasive bladder cancer, the tumor extends beyond

the inner lining and penetrates the muscular wall of the organ.

It accounts for about 25% of all newly diagnosed bladder cancers

and is a particularly aggressive form with a high risk of

spreading, according to the National Institutes of Health.

Pfizer ( PFE ) said it plans to discuss the trial results with

global health authorities for potential regulatory filings.

The combination therapy leverages anti-PD-1 treatments that

block the PD-1 protein to help the immune system combat cancer,

where Padcev, an antibody-drug conjugate, targets specific

cancer cells without damaging healthy ones.

Padcev, co-developed with Japan's Astellas, was

approved by the U.S. Food and Drug Administration in 2019 to

treat patients with a form of bladder cancer called metastatic

urothelial cancer.

The drug brought $1.59 billion in sales last year,

contributing about 2% of Pfizer's ( PFE ) total revenue.