Unfortunately, having a "cancer spot" disappear can't be ascertained as a miracle. Many people believe that it's very common for cancers to appear and disappear many times during people's lifetimes and think that most people get a touch of cancer here and there during their lives, but their body fights it off. But anything is good enough for Novus Ordo canonizations. I doubt that Father's case would ever see the light of day anyways due to the hostility towards the Traditional Mass in Rome.