Radiotherapy, surgery and chemotherapy are the mainline treatments for patients with breast cancer. As a treatment modality, radiotherapy has many roles to offer these patients. These include treatment of the breast after a partial mastectomy in order to conserve the breast and treatment of the chest area after a total mastectomy in order to decrease the chance of the cancer recurring in that area. In both these situations radiation may also be given to the lymph node regions around the breast in order to prevent a relapse in these sites. Many studies have demonstrated that radiotherapy given in these settings decreases the chance of the cancer recurring and increases the probability of cure for the patient. Another role for radiotherapy is in treating recurrences of breast cancer, either in the chest area or elsewhere in the body known as metastasis. Radiotherapy is very effective at remitting these secondary lesions and relieving associated symptoms leading to an improved quality of life.
Along with surgery and chemotherapy, radiotherapy is becoming more targeted, providing more punch to the cancer cells and less to the normal cells. This is partly due to improved diagnostic imaging which provides us better localization of targets for the radiotherapy and partly due to improved technology in radiotherapy which allows us to conform the dose of radiation to these targets more precisely. The goal in developing a plan of radiotherapy for a patient is to develop the plan with the maximum therapeutic ratio, namely the ratio of the dose to the cancer target to the dose delivered to normal tissues.
Compared to conventional x-ray therapy, proton beam radiotherapy generally provides a greater therapeutic ratio. This is due to the fact that whereas x-rays will travel the entire thickness of the part of the body they are aimed at, protons will only travel a limited distance in the body depending on their energy. The energy imparted to a proton and its direction of travel can be very precisely set and thus the range of the proton beam in the body can be carefully limited. In breast cancer this allows us to thoroughly treat the breast or chest area and the lymph nodes while substantially limiting the dose of radiation to the heart and lung compared to x-ray therapy. This will lead to decreased heart and lung disease later in the patient’s life. With more and more patients being cured of their breast cancer, reducing these preventable medical conditions becomes even more important. As proton beam radiotherapy becomes more generally available, more and more patients will be able to take advantage of this safer treatment option. Proton beam has a more limited role in treating patients with metastatic breast cancer, though frequently is considered when a patient needs retreatment of a previously radiated area. Because the volume of tissue receiving this second course of radiotherapy can be better limited with proton beam, it can be the less risky treatment option for these patients.
Dr. Allen Meek is Medical Director of Provision Medical Group and a board-certified radiation oncologist practicing at Provision Radiation Thearpy and Provision Center for Proton Therapy. Dr. Meek was recognized as a 2012 U.S. News and World Report “Top Doctor” and one of the Best Doctors in America® for 2014.