Legal Question in Wills and Trusts in Pennsylvania

Generally there is no difference as long as the person has the capacity to make a will. This means that as long as the person is an adult (over 18 in PA) and is aware of the consequences of his or her conduct in drafting the will, the will is valid. Usually this involves knowing the identity and extent of their possessions, beneficiaries and any responsibilities they might have.

In order to challenge the validity of the will drafted while the person was on cancer medication you would need to show in court that the lacked the capacity to make a will because of the effect of the cancer medication on his mental ability to properly draft a will. Keep in mind that this is generally very difficult to prove especially if the will had a self proving affidavit with witnesses to the signing of the will.

You don't tell me why what kind of drugs they were taking or what type of cancer they had or what kind of treatment was administered. The question is going to be, did they have sufficient testamentary capacity to make a will while they were in the hospital? If they did not, then you can bring a challenge to the the will. The challenge is called a caveat. And if a successful will caveat is brought, it will not necessarily revive the old will and the assets may pass through intestacy. If that happens, who will be among the intestate heirs? Will you be included? And how much money or assets are at stake? This may dictate whether you bring a will caveat or not. You will have to be prepared to know what the doctors and nurses would say about the person's mental state - if the person was sick, but mentally healthy, then a challenge is not going to be successful.