Radiotherapy

Radiotherapy is the use of ionising radiation to damage and kill tumour cells. Radical radiotherapy involves using radiotherapy to cure the tumour. It may be combined with chemotherapy before, during or after radiotherapy. Adjuvant radiotherapy, for example following surgery to remove a tumour, is given to eradicate residual tumour 

Radiotherapy is a local treatment aiming to achieve local control or cure of locally confined tumours. It cannot treat metastases. Radiotherapy may be administered as external beam radiotherapy with X-rays or gamma rays, in sealed radioactive sources (e.g. prostate brachytherapy), or unsealed sources (e.g. orally administered radioiodine for thyroid cancer, intravenous strontium-89 for bone metastases). In external beam radiotherapy, the X-ray or gamma ray beams are targeted at the tumour to damage and kill the tumour cells. Inevitably, surrounding normal tissues are also affected resulting in the early and late side effects of radiotherapy. 

Some people wonder how radiation— which is known to cause cancer—can be used to treat cancer. The answer lies in risk analysis. A cancer patient is normally exposed to radiation doses of about 100 rem. Such a dose increases cancer risk by about 1%. However, if the pahent has a 100% chance of dying from the cancer that he or she already has, such a risk becomes acceptable, especially since there is often a significant chance of curing the cancer. 

A FIGURE 17.14 Radiotherapy for cancer This treatment involves exposing a malignant tumor to gamma rays, t)q)ically from radioisotopes such as cobalt-60. The beam is moved in a circular pattern around the tumor to maximize exposure of the cancer cells while minimizing exposure of healthy tissues. 

Which t)qje of radiation is most likely to be used for isotope scanning  

The Nature and Discovery of Radioactivity Radioactivity is a fundamental part of the behavior of some atoms, and it also has many applications. For example, radioactivity is used to diagnose and treat diseases, including cancer, tii5uroid diseases, abnormal kidney and bladder function, and heart disease. Natural radioactivity is part of our environment and can be used to date ancient objects. The discovery of radioactivity led to the discovery of fission, which in turn led to the development of nuclear bombs and nuclear energy. 

Detecting Radioactivity Since radioactivity is invisible, it must be detected using film or instruments. The detection of radioactivity is important as both a scientific tool and a practical one. Our understanding of what radioactivity is and our continuing research to understand it and its effects on living organisms require the ability to detect it. Our safety in areas where radioactive substances are used also depends on our ability to detect radiation. 

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The immunorestorative potential of inosiplex has been evaluated in several clinical conditions, including post-surgical trauma, cancer patients with concurrent viral infections, and cancer patients receiving radiotherapy or chemotherapy. For example, most (84%) of the surgery patients remained immunologicaHy depressed, but 56% of the inosiplex-treated surgery patients had complete restoration of normal skin test reactivity (probability level < 0.0005). The use of inosiplex as an adjuvant to chemotherapy or radiotherapy appears to be valuable in the prophylaxis against opportunistic infections. 

Modem cancer therapy has been primarily dependent upon surgery, radiotherapy, chemotherapy, and hormonal therapy (72) (see Chemotherapeutics,anticancer Hormones Radiopharmaceuticals). Chemotherapeutic agents maybe able to retard the rate of growth, but are unable to eradicate the entire population of neoplastic cells without significant destmction of normal host tissue. This serious side effect limits general use. More recentiy, the immunotherapeutic approach to cancer has involved modification and exploitation of the cellular and molecular mechanisms in host defense, regulation of tissue proliferation, tissue differentiation, and tissue survival. The results have been more than encouraging. 

Cancer or neoplastic disease is a genomic disorder of the body s own cells which start to proliferate and metastasize in an uncontrolled fashion that is ultimately detrimental to the individual. Antineoplastic agents are used in conjunction with surgery and radiotherapy to restrain that growth with curative or palliative intention. The domain of antineoplastic chemotherapy is cancer that is disseminated and therefore not amenable to local treatment modalities such as surgery and radiotherapy. 

Cancer treatment is a multimodality treatment, i.e., surgery is combined with radiotherapy and antineoplastic chemotherapy. The latter treatment mode is used mainly for cancers which have disseminated. Different forms of cancer differ in their sensitivity to chemotherapy with antineoplastic agents. The most responsive include lymphomas, leukemias, choriocarcinoma and testicular carcinoma, while solid tumors such as colorectal, pancreatic and squamous cell bronchial carcinomas generally show a poor response. The clinical use of antineoplastic agents is characterized by the following principles. 

The Antiemetic Subcommittee of the Multinational Association of Supportive Care in Cancer (2006) Prevention of chemotherapy- and radiotherapy-induced emesis results of the Perugia International Antiemetic Consensus Conference. Ann Oncol 17 20-28... 

Several cytokines are in clinical use that support immune responses, such as IL-2, DFNs, or colony-stimulating factors. IL-2 supports the proliferation and effector ftmction of T-lymphocytes in immune compromised patients such as after prolonged dialysis or HIV infection. IFNs support antiviral responses or antitumoral activities of phagocytes, NK cells, and cytotoxic T-lymphocytes. Colony-stimulatory factors enforce the formation of mature blood cells from progenitor cells, e.g., after chemo- or radiotherapy (G-CSF to generate neutrophils, TPO to generate platelets, EPO to generate erythrocytes). 

Somatostatin Receptor Scintigraphy and Receptor-Targeted Radiotherapy... 

Note that application in the particular indications is usually restricted either to patients expressing the target (e.g. trastuzumab, cetuximab, lapatinib, imatinib) and/or after failure of prior therapies (e.g. cetuximab, erlotinib, lapatinib, sutinib, dasatinib). Furthermore, for cancer treatment most tyrosine kinase inhibitors are applied in combination with conventional chemotherapeutic drugs, such as fluorouracil, taxanes, platin-based regimens, anthracylines and irinotecan or radiotherapy. 

Anticoagulants History of local radiotherapy History of Keloid formation Pregnancy/breast-feeding Heavy smokers... 

The Chilkoti group applied the local injection approach for intratumoral dmg delivery. ELP[V-120], with a transition at 27°C, was designed and labeled with C, 1 or 1 for radiotherapy. The first two labels were used to monitor tumor retention of the ELP and the last label was addressed to equip the ELP with antitumor activity. It was found that mice treated with 1-labeled ELP[V-120] experienced a significantly prolonged survival over those treated with saline [97]. 

Male infertility may result from cancer surgery, radiotherapy, hormonal imbalances, or damage of germinal stem cells. Testicular damage from radiotherapy depends on the treatment field, total dose, and fractionation schedule. Depending on the radiation, sperm counts may return to pretreatment levels in 10 to 24 months after therapy or maybe permanent in 80% of men after total-body irradiation for transplant. 

Tumor Type Percent of Tumors Approximate Cell Doubling Time Sensitivity to Chemotherapy and Radiotherapy Relative Risk of Metastasis... 

Chemo, chemotherapy NSCLC, non-small cell lung cancer PORT, postoperative radiotherapy TNM, tumor node metastasis. 

The term adjuvant therapy refers to the use of chemotherapy or radiotherapy following surgical resection of a tumor mass. The rationale behind adjuvant chemotherapy is to eradicate micrometastases or other tumor cells that may have been missed during removal of the primary tumor. The recent results of five relatively large prospective trials (n = 344—1867) suggest that there is benefit from adjuvant chemotherapy. The largest study, the International Adjuvant Lung Trial (IALT),24 has led to the... 

Small cell lung cancer typically presents as extensive disease (approximately 60% to 70% of new cases) and progresses very quickly. Small cell carcinomas are very responsive to chemotherapy and radiation. Radiotherapy became the standard in 1969, when a randomized trial showed that it offered the potential for cure, whereas surgery did not.20 For the vast majority of patients, chemotherapy with or without radiotherapy is the treatment of choice. Even after a complete response to therapy, the cancer usually recurs within 6 to 8 months, and survival time following recurrence is typically short ( 4 months). This yields a typical survival rate of 14 to 20 months for limited disease and 8 to 13 months for extensive disease.33 Table 87-6 illustrates the general treatment path of SCLC. 

The two commonly used methods for radiation therapy are external-beam radiotherapy and brachytherapy.26 In external-beam radiotherapy, doses of 70 to 75 Gy are delivered in 35 to 41 fractions in patient with low-grade prostate cancer and 75 to 80 Gy for those with intermediate- or high-grade prostate cancer. Brachytherapy involves the permanent implantation of radioactive beads of 145 Gy of 125I or 124 Gy of 103Pd and generally is reserved for individuals with low-risk cancers. 

Secondary or salvage therapies for patients who progress after their initial therapy depend on what was used for initial management.26 For patients diagnosed initially with localized prostate cancer, radiotherapy can be used in the case of failed radical prostatectomy. Alternatively, androgen ablation can be used in patients who progress after either radiation therapy or radical prostatectomy. 

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