To treat a pituitary tumor with radiation, doctors may use a variety of techniques depending on the size and location of the tumor. Conventional radiation covers a wide area in and around the tumor and is usually given daily for several weeks.
In the show, Stannis Baratheon dies under the sword of Jamie Lannister, wielded by a woman to fulfill a promise to Catelyn Stark, to avenge the death of Renly Baratheon. You can state he died of internal complications.
King Joffrey Baratheon died at just 19 years old in the episode The Lion and the Rose, at his wedding feast after he was poisoned. He choked to death after being handed a poisoned glass of wine. He is survived by Cersei Lannister, his mother and aunt, and Jaime Lannister, his biological father and uncle.