When cancerous tumors appear, the best thing to do with them is to destroy the tumor and any cancerous residue. Killing the cancer is not difficult. The problem is that the methods used to kill the cancer also kill healthy tissue. The trick then becomes killing the cancer whilst sparing the patient.
One of the most significant recent advancements in cancer treatment is Intensity Modulated Radiation Therapy, or IMRT. If tumors were square and were never located near healthy or vital tissue, then IMRT wouldn’t be necessary. However, since tumors tend to come with curves and often are very close to tissue that one doesn’t want to damage, the IMRT plays a significant role in lessening damage to surrounding healthy tissue.