RATIONALE: Erlotinib may stop the growth of tumor cells by blocking the enzymes necessary for their growth. Radiation therapy uses high-energy x-rays to kill tumor cells. Stereotactic radiosurgery may be able to deliver x-rays directly to the tumor and cause less damage to normal tissue. Erlotinib may make tumor cells more sensitive to radiation therapy. Giving erlotinib together with stereotactic radiosurgery may kill more tumor cells.