Radiation oncology has been a specialty of oncology for more than 100 years. It uses ionizing radiation for curative or palliative (pain-relieving) treatment of cancer patients. It involves the study of radiation effects on both malignant and normal tissues.
Diagnostic imaging is an important component of radiation oncology. Radiation serves as a targeted local therapy in the treatmentment of cancer. But to treat a cancer, a radiation oncologist must know where that cancer is located.
The basic goal of radiation therapy is to focus a beam of radiation on the tumor at doses that will destroy it without damaging surrounding healthy tissue. In recent years, major advances in technology have given radiation oncologists the ability to administer higher doses to more exact areas of the body with less toxicity.
During treatment, if patient movement occurs, the highly accurate dose may miss the tumor and treat more normal tissue. So the patient is immobilized to keep him or her in the same position.
Radiation treatment for breast cancer varies according to the cancer stage. In early stage breast cancer, radiation oncologists may use accelerated partial breast irradiation (APBI) to deliver large doses of radiation to the lumpectomy cavity after breast-conserving surgery. Radiation therapy is completed in 5 days instead of 6-7 weeks.
Radiation oncologists may also use partial breast irradiation (brachytherapy) in patients with early-stage breast cancer.
For advanced stage breast cancer, more comprehensive radiotherapy is indicated. Treatment options include intensity-modulated radiation therapy (IMRT), an advanced form of conformal radiation therapy. The basic idea of IMRT is that beam intensity is made proportional to the target thickness – where the target is "thickest,” beam intensity is increased and where the target is “thinnest,” or where critical structure is in pathway, beam intensity is decreased. Thus, ideally, radiation oncologists can deliver highly accurate doses to treat tumors and spare normal tissues.