Tell or not tell?

Apple is an experienced nurse who works on a mixed ward which caters mainly for cancer sufferers at various stages of their treatments. Apple is a Catholic and very single minded about telling the truth. She has a patient called John who is diagnosed as having lung cancer just a few days ago. John’s relatives come to Apple and tell her that they do not want John to know he is diagnosed with lung cancer. The relatives also show her a medical judgement which indicates that the truth would cause John psychological damage. However, when Apple comes back to the ward, John keep asking her what happens to him and why he needs to do the treatment. Should Apple tell John the truth?