Linear accelerator and cancer
A linear accelerator (linac) is a specialized machine used in radiation therapy to generate high-energy X-rays and electrons aimed at destroying cancer cells and reducing tumor size. This treatment targets most solid-tumor cancers, including breast, colorectal, prostate, and brain cancers, as well as blood cancers like leukemia and lymphoma. The process begins with the patient undergoing imaging tests to pinpoint the tumor location, which is then loaded into a treatment-planning computer.
Typically, patients receive treatment five days a week over a span of four to six weeks, with the procedure being quick and painless. While the linac works, patients lie still on a treatment table, often under the supervision of trained staff who monitor the process via an intercom system. Although the treatment usually occurs on an outpatient basis, side effects can vary depending on the area treated, potentially including skin irritation, fatigue, and other localized symptoms. Ultimately, when integrated into a comprehensive care plan, radiation therapy with a linear accelerator can be a critical component in achieving effective control or even a cure for cancer.
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Linear accelerator and cancer
ALSO KNOWN AS: Linac, radiation therapy machine
DEFINITION: A linear accelerator (linac) is a machine that produces high-energy X-rays and electrons to kill cancer cells and shrink tumors. The beam of a linear accelerator is shaped and sized to treat the tumor and protect surrounding normal tissue.
Cancers treated: Most solid-tumor cancers, such as breast, colorectal, prostate, and brain cancers; leukemia and lymphoma; cancer symptom management
Why performed: External radiation used to kill cancer cells at the site of the tumor provides effective local cell death and discourages regrowth.
Patient preparation: A computed tomography (CT) scan or other radiology test is done to determine the tumor site to be treated. The doctor, a radiation oncologist, reviews the patient’s chart and marks the tumor site. This information is loaded into a treatment-planning computer that calculates how much radiation the patient will receive. The calculations are then programmed into the linear accelerator. The treatment planning may take several hours. Patients may also be fitted with positioning devices that help to hold the body still during treatment. Some linacs have gantry-mounted cone-beam CT (CBCT) systems that help ensure proper patient positioning. Prostate cancer patients may undergo a minimally invasive, pre-treatment procedure to inject a liquid hydrogel spacer material between the prostate and rectum. The extra space created allows the reduction of rectal toxicity.
Steps of the procedure: Treatments on the linear accelerator are usually given once a day for four to six weeks. Treatments are not usually given on Saturday and Sunday to allow normal cells to recover. Patients change into gowns or wear street clothes depending on the site being treated. The staff carefully positions the patient on the treatment table or chair. The staff leaves the room, but an intercom allows the patient to call for help if needed. The painless treatment takes just a few minutes, during which the patient must lie still. The equipment is noisy as it rotates around the patient, and the treatment table may move. Treatments are usually outpatient, and patients return home each day.
After the procedure: Once all treatments are complete, the patient will see a doctor to determine the status of the tumor and plan any necessary follow-up treatment. It is safe for the patient to be around others, including children and pregnant women, because no radiation is in the body.
Risks: Side effects depend on the site treated and may include redness and skin irritation, urinary symptoms, diarrhea, fatigue, eating problems, shortness of breath, and hair loss at the treatment site.
Results: External radiation from a linear accelerator provides effective local control of cancer cells. As part of a comprehensive plan of care, radiation therapy can lead to a cure.
Bibliography
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Johnson, George. The Cancer Chronicles: Unlocking Medicine's Deepest Mystery. Knopf, 2013.
Liu, Xin, et al. “Clinical Application of MR-Linac in Tumor Radiotherapy: A Systematic Review.” Radiation Oncology (London, England), vol. 18, no. 1, 14 Mar. 2023. doi:10.1186/s13014-023-02221-8.
Shastry, Shamee, at al. "Linear Accelerator: A Reproducible, Efficacious and Cost Effective Alternative for Blood Irradiation." Transfusion & Apheresis Science, vol. 49, no. 3, 2013, pp. 528–32. doi:10.1016/j.transci.2013.03.007.
Weinberg, Robert A. The Biology of Cancer. 3rd ed., W. W. Norton & Company, 2023.