I'll try to answere you questions the best I can. First, radiation therapy is not as toxic as chemotherapy. Radiation is local, which means it only affects the area we treat. The area within those marks is the only place he will experience side effects from the radiation therapy treatments.
Chemotherapy is systemic treatment which means it goes throughout the whole body.
That's why people loose their hair and experience other side effects from the chemo. Radiation therapy treatments that are delivered by a big machine, called a Linear Accelerator, are external beam therapies. Sometimes Radiation Oncologists, doctors who prescribe and are specialized in radiation therapy, can do brachytherapy treatments. In the case of a lung tumor, the physician would introduce a strand of seeds in through the lungs via the mouth. It is a relatively simple procedure that is very quick and can be done usually in a Radiation Oncology Department.