Former President Biden said Friday afternoon that he was feeling good after beginning his treatment for an aggressive form of prostate cancer.

“The prognosis is good,” he said.

“We’re working on everything. All the folks are optimistic,” he added, referring to his medical team.

Mr. Biden spoke to reporters after an event honoring veterans in New Castle, Del. They were his first public remarks since May 18, when his office announced the diagnosis and said the cancer had metastasized to the bone.

Mr. Biden said that his treatment was “all a matter of taking a pill, one particular pill.”

“The expectation is we’re going to be able to beat this,” he said.

Mr. Biden’s cancer was given a Gleason score of 9. The score is used to describe how prostate cancers look under a microscope; 9 and 10 are the most aggressive.

Mr. Biden, 82, left office in January as the oldest-serving president in American history.