Should my boyfriend go back on fin? Will he get sexual sides if he didn’t get them before?

Posting for my ‘off-the-grid’ boyfriend. He took fin in his mid twenties. It worked great, and he had no sexual sides. He stopped cause he was afraid of cancer. Now that the 2018 follow up study came out, he’s thinking about going back on. Do you think he has less risk of developing sexual sides cause he didn’t before? If he goes on it and has sides, will they disappear when he goes off? Should he go on it?