How are chemotherapy and radiation therapy different?

Local v. Systemic Rx: Some cancers require multimodal therapy to attack the organ where the cancer started and where it may have spread. Chemotherapy is like antibiotics: it travels throughout the body, ideally killing any cancer cells encountered. Radiation therapy is concentrated to one local area, and may be given "outside-in" (external beam) or "inside-out" (brachytherapy). These 2 rx complement each other.

X-rays versus drugs: Radiation is a beam of energy that comes from aimable machines through the air. Chemotherapy is drugs given into veins or by oral pills. So one goes through air and the other in the blood.

Very: A common question. Both can damage dna, but chemotherapy accesses most body parts (not the brain). Developing molecularly taraget agents may go after a very specific cancer vulnerability - a genetic acquired mutation. Radiotherapy only works where it is aimed, beneficially and side-effects too.