Mr. Robin has lost his wife and recently been diagnosed as a cancer patients. He is depressed for losing his beloved wife. Furthermore he has been diagnosed as a cancer patients. In this situation, he feels that it is unbearable to cope with serious pain as long as live because of cancer. So it is better to suicide for getting rid of pain. It's not right decision ethically to commit suicide himself. According to Jean Jacques Rousseau, every man has right own risk in order to preserve himself. Ethically suicide is a immoral work. If we think in the religious view, religion does not approve to kill himself.
Mr. Robin emotionally decide to kill himself, but it not right decision ethically. He should take treatment as per possible. If it is really unbearable, he can admit in palliative care. Cause suicide create bad example in the society. It make frustration to the neighbours. He should pray to almighty to reduce the pain and get rid of unbearable pain. He should never do this immoral work at all.
If Mr. Robin goes to hospital and express his desire to doctor by drug. If doctor see that the patient genuinely suffer serious pain. It will make ethical dilemma. But according to the professional ethics of the doctor, he should not agree with the decision of the patient rather he should take necessary steps to reduce the pain. He can send him in palliative care until his natural death. I think it will be more ethical decision.