Radiation Therapy for Cancer

More than 14 million new cases of cancer are diagnosed globally each year; radiation therapy (RT) has the potential to improve the rates of cure of 3.5 million people and provide palliative relief for an additional 3.5 million people. These conservative estimates are based on the fact that approximately 50 percent of all cancer patients can benefit from RT in the management of their disease (Barton, Frommer, and Shafiq 2006; Barton and others 2014; Tyldesley and others 2011); of these, approximately half present early enough to pursue curative intent. Soon after Roentgen’s discovery of X-rays in 1895, ionizing radiation was applied to the treatment of cancer, with remarkable results. Carefully controlled doses of ionizing radiation induce damage to the DNA in cells, with preferential effects on cancer cells compared with normal tissues, providing treatment benefits in most types of cancer and saving lives. RT is now recognized as an essential element of an effective cancer care program throughout the world, regardless of countries’ economic status. RT is used to cure cancers that are localized; it also can provide local control—complete response with no recurrence in the treated area—or symptom relief in cancers that are locally advanced or disseminated (Gunderson and Tepper 2012). It is frequently used in combination with surgery, either preoperatively or postoperatively, as well as in combination with systemic chemotherapy before, during, or subsequent to the course of RT (Barton and others 2014). Because radiation affects normal tissues and tumors, achieving an acceptable therapeutic ratio—defined as the probability of tumor control versus the probability of unacceptable toxicity—requires that the radiation dose be delivered within very tightly controlled tolerances with less than 5 percent deviation. This controlled production and precise application of radiation requires specialized equipment that is maintained and operated by a team of trained personnel. The team includes, at a minimum, radiation oncologists to prescribe the appropriate dose, medical physicists to ensure accurate dose delivery, and radiation technologists to operate the equipment and guide patients through the radiation process. Radiation oncologists work within multidisciplinary teams with medical and surgical oncologists to coordinate a multidisciplinary approach to the management of cancer. A comprehensive cancer center provides the full scope of RT services, ranging from externally applied beams of X-rays to the placement of radiation-emitting sources within tumors (see chapter 11 in this volume [Gospodarowicz and others 2015]). RT is one of the more cost-effective cancer treatment modalities, despite the need for substantial capital investment in the facilities and equipment. Concerns about the initial investment, however, have resulted in severely limited access in most low- and middle-income countries (LMICs). Increasing the supply of RT services is critical to expanding effective cancer treatment in these settings and improving equity in access (Abdel-Wahab and others 2013; Fisher and others 2014; Goss and others 2013; Jaffray and Gospodarowicz 2014; Rodin and others 2014; Rosenblatt and others 2013).