PSA test results after radiotherapy

Hi I am wondering what this all means, my husband had radiotherapy Gleason score 7, 3 plus 4, all went well, this was 2 years ago, stopped hormone tablets 2 months after radiotherapy. His PSA results every six months arena from the first one after radiotherapy,  0.28, 0.21, 0.25, 029, 0.49, due again in 6 months time, worried that it is increasing, Christies said it can be normal healthy prostrate tissue and not taking hormone tablets, wondering if any one has experienced this and their outcomes