Combination strategies using immunotherapies and genetic procedures in conjunction with chemotherapies, radiation therapies, and surgery are being viewed as the hope for future successes in cancer treatments.
Chemotherapy and radiation therapy differ from immunotherapies and cellular genetic therapies in that immunotherapies use the body’s own cells (and intrinsic biologic agents) to treat itself. Conversely, chemotherapies utilize toxic biochemical agents to target and destroy tumor and cancer cells throughout the body. The problem with chemotherapy (and radiation therapy) is their indiscriminate, adverse effects on healthy tissue and organ systems. Various forms of chemotherapeutic agents effectively disrupt the stages of irregular and rapid cancer cell development. Unfortunately, they are not specific to the cancer cells alone and tend to disrupt normal cell cycles as well, particularly the more susceptible cells of the gastrointestinal tract and hair follicles, thus causing nausea and hair loss in cancer patients. Used in conjunction with surgery and/or radiation therapy, chemotherapy is referred to as neoadjuvant and when used after surgery and/or radiation therapy, it’s called adjuvant therapy. Both neoadjuvant and adjuvant therapies help other treatments work better and kill cancer cells that have returned or spread to other parts of the body.
Radiation therapy targets and attempts to destroy tumors and cancer cells in specific areas of the body by using beams of intense energy to kill the cancer cells. X-rays, proton beams, and other types of energy are now being used with considerable success. The radiation is delivered by an external beam or by an internal source (usually solid radioactive media) placed near the tumor. Brachytherapy, radioactive implants directly into the tissue is most often used to treat cancers of the head and neck,
breast, cervix, prostate, and eye. Systemic radiation therapy called radioactive iodine, or I-131 is most often used to treat certain types of thyroid cancer. Another type of systemic radiation therapy called targeted radionuclide therapy or molecular radiotherapy is used to treat some patients who have advanced prostate cancer or gastroenteropancreatic neuroendocrine tumors (GEP-NET). Whatever the delivery mode, at high doses, radiation kills cancer cells or damages their DNA and causes the cancer cells to stop dividing or die. This process could take days or weeks before DNA is damaged sufficiently to destroy the cancer cells. Subsequently, the cancer cells keep dying for weeks or months after radiation therapy ends.
Target therapies for cancer are similar to the immunotherapies that use biologic agents for autoimmune diseases. The agents used differ from chemotherapeutic drugs in that they interfere with specific “molecular targets” that are involved in the growth, and the spread of cancer. Targeted cancer therapies are sometimes called “molecularly targeted therapies” and “precision medicines” by virtue of their target specificity, similar to genetic therapies. As such, they are considered cornerstones in the “precision medicine” concept. Some of the FDA approved target therapies include hormone therapies, signal transduction inhibitors, gene expression modulators, apoptosis inducers, angiogenesis, and checkpoint inhibitors.
But currently, notwithstanding the effective use of combined cancer-fighting technologies, immunotherapies are becoming increasingly favored as first-line treatment choices. The main reasons appear to be better results in arresting and even reversing tumor growth and metastasis as well as reducing negative treatment sequelae.
Discussion Questions:
Chemotherapy is used frequently with radiation therapy for various forms soft cancer. Which therapy is almost always administered first and for what reason(s)?
Radiation therapy has significant benefits in certain types of tumors. Given the nature of its delivery mode, can you name some cancers for which it is contraindicated?
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