The rays are directed very closely to the tumor. How the rays will adversely affect normal tissues depends on how large an area is being irradiated and its proximity to the tissues. For example, radiation to tumors of the head and neck often causes inflammation of the mucous membranes in the nose and mouth, resulting in soreness and ulcerations. For early cancers of the larynx and prostate, the rate of cure is essentially the same with radiation therapy as with surgery. Radiation therapy can reduce symptoms when a cure isn't possible, as in multiple myeloma and advanced lung, esophageal, head and neck, and stomach cancers.
Radiation therapy can also relieve symptoms caused by metastases to the bones or brain.
Although an ideal anticancer drug would destroy cancer cells without harming normal cells, no such drug exists. Today the side effects of chemotherapy can be minimized. Often, two or more drugs are used in combination. The rationale to combination chemotherapy is to use drugs that work at different parts of the cell's metabolic processes, thereby increasing the likelihood that more cancer cells will be killed. In addition, the toxic side effects of chemotherapy may be reduced when drugs with different toxicities are combined, each at a lower dose than would be needed if one drug were used alone.