Microsoft co-founder and pro sports mogul Paul Allen will continue his battle with cancer.

The owner of the NFL's Seattle Seahawks and NBA's Portland Trail Blazers announced on Monday the first and last week.

Allen, 65, said he's optimistic the advances in cancer treatment in the nine years since he was originally diagnosed with the disease.

After becoming a billionaire when Microsoft went public, Allen bought the Blazers Trail in 1998 and the Seahawks in 1996, in addition to his other business ventures.

"I will continue to be involved with Vulcan, the Allen Institutes, the Seahawks and Trail Blazers," he said in a statement.

The latest rankings for Forbes magazine has Allen as the 44th-richest person in the world, with a net worth of about $ 20.2 billion.