Former U.S. President Joe Biden has entered a new phase in his battle with prostate cancer: he is now undergoing radiation therapy in conjunction with hormone treatment. Earlier this year, in May, he was diagnosed with an aggressive prostate cancer that had already metastasized to his bones.

Medical tests placed the cancer at a high Gleason score of 9, signaling that the cancer cells are highly abnormal and likely to grow more quickly than in less aggressive forms. 

The radiation therapy is expected to span five weeks, according to a statement from his office. Before this, Biden had been taking hormone medication in pill form. His doctors say the cancer is “hormone-sensitive,” which means that despite its aggressiveness and spread, it is likely to respond well to treatments that lower or block male hormones. 

Biden is 82 years old and will celebrate his 83rd birthday soon. He also recently had a Mohs skin surgery procedure to remove cancerous skin cells from his forehead.

Though the cancer has spread to his bones, his medical team considers that many forms of therapy remain possible and is treating it aggressively. Despite the seriousness of the diagnosis, Biden is said to be doing well under treatment.