The 12 Rounds star reveals one of his siblings has been undergoing treatment and he's making great progress in his fight against the potentially deadly disease, thanks to doctors' early diagnosis.
Cena recently joined forces with bosses at the Susan G. Komen for the Cure organisation to raise awareness about the importance of regular health check-ups, insisting it really can be the difference between life and death.
He says, ""A year ago my brother was diagnosed with Stage 3 inoperable brain cancer. But, believe it or not, hopefully, if everything goes well, by November this year he will be in remission.
""A lot of the reason (why) they were able to catch it and treat it is early detection... The sooner you can detect it, you do have a chance of survival - my brother is living proof.""