Cognitive function in children with leukemia: effect of radiation dose and time since irradiation

Article Abstract:

Perhaps the most important advance in the treatment of acute lymphoblastic leukemia (ALL) in children was the inclusion of the brain in the treatment. Many anticancer drugs do not penetrate the brain effectively, and a small handful of leukemic cells in this organ served to seed the relapse and ultimate death of many children. Now, however, it is standard procedure to supplement the antileukemic therapy with radiation to the head to destroy any remaining leukemic cells hiding there. Early studies found that the intellectual development of the children treated in this way was slightly impaired; the effects of treatment seemed to be more severe among the children who were youngest at the time of treatment. Efforts were spent trying to reduce this undesirable effect of treatment; of course, if the radiation dose is lowered too much, the child is likely to die of leukemia and intellectual development is of little consequence. Today, it is generally recommended that the dose of radiation delivered to the head be no more than 2,400 cGy and no less than 1,800 cGy. (A Gy, or Gray, is a dose of radiation equivalent to one joule of energy absorbed per kilogram of tissue. It is equal to 100 rads.) A study was conducted specifically to examine the effects of radiation on intellectual development across this dose range. Twenty children who received doses of 2,400 cGy and 15 children treated with 1,500 cGy were given tests of verbal intelligence, as well as tests of reading, spelling, and arithmetic. The intelligence of the children receiving the higher dose of radiation was, on the average, about 20 points lower than the children receiving the lower dose. However, these children had received their radiation doses further in the past, and the difference in scores was found by statistical analysis to be related to the time interval between treatment and testing rather than to the actual radiation dose. Although the scores were lowered, it should be emphasized that they were still within the normal range. The results of this study indicate that mild deficits in intellectual performance resulting from radiation therapy may appear slowly over long periods of time. This illustrates the importance of performing longitudinal studies, in which individual children are followed carefully over long periods, to determine the precise intellectual impairments caused by cranial radiation therapy. (Consumer Summary produced by Reliance Medical Information, Inc.)

Care and treatment, Physiological aspects, Cognition, Cognition disorders, Cognitive disorders, Childhood leukemia, Leukemia in children

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Exacerbation of psoriasis after megavoltage irradiation: the Koebner phenomenon

Article Abstract:

Megavoltage irradiation, indispensable in the treatment of some cancers, is considered to be relatively sparing of the skin. Recently, however, a case was reported in which megavoltage irradiation resulted in the appearance of the Koebner phenomenon, which is the appearance of new psoriatic lesions in an area of damaged skin. The most remarkable feature of the response is that the psoriatic area matches the injured area precisely. For this reason, the Koebner phenomenon is also frequently referred to as the "isomorphic" response. The patient, a 66-year-old male, had been diagnosed with lung cancer, which was surgically treated. He had been treated for psoriasis in the past, but had received no treatment in the five years preceding the operation for lung cancer. Several months after surgery, the patient experienced severe pain in the thigh, and X-ray examination revealed a lesion consistent with a metastatic tumor. A sample removed from the femur confirmed the presence of metastatic cancer, and the patient was treated with 3,000 cGy irradiation of six megavolt gamma rays (a Gy, or Gary, is one Joule of energy absorbed per kilogram of tissue). The patient experienced only a modest reduction in pain. However, he also developed severe itching and crusting of a scaly lesion. An additional radiation dose of 3,000 cGy was given in an attempt to reduce the patient's pain. The reduction in pain resulting from the second dose of radiation was minimal, but the skin lesions evolved to take on the appearance of typical psoriasis. The distribution of psoriatic lesions on the skin matched the irradiated area exactly, and was thus considered to be an example of the Koebner phenomenon. The pathologic process underlying psoriasis is poorly understood, but it is clear that the skin cells forming psoriatic lesions multiply abnormally fast, perhaps seven or eight time faster than normal. The present case would suggest that while megavoltage radiation has little effect on the skin in healthy patients, for patients with underlying skin problems, the radiation may precipitate pathological cell proliferation and psoriasis. (Consumer Summary produced by Reliance Medical Information, Inc.)

Psoriasis

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Morphologic changes in the thyroid after irradiation for Hodgkin's and non-Hodgkin's lymphoma

Article Abstract:

Radiation exposure of the thyroid gland during childhood has been associated with the development of thyroid cancer later in life. It has been estimated that even low dose radiation exposure (less than 1,500 rad) may result in cancer of the thyroid gland. It is believed that widespread low-dose radiation exposure has caused an increased incidence of thyroid cancer among adults who were exposed to these levels of radiation as children. This study reports the cases of four patients who exhibited thyroid nodules from 8 to 20 years after high-dose radiation to the head and neck for treatment of non-thyroid cancers: Hodgkin's and non-Hodgkin's lymphomas. A variety of structural changes (morphological) of the thyroid gland were noticed in these patients; the most pronounced abnormality was the presence of multiple adenomatous nodules (swelling of the lymph nodes). Many of these nodules were surrounded by thick, fibrous capsules. Although this pattern has been described after low-dose radiation therapy for benign conditions, it has not been well documented after high-dose radiation therapy. It appears that high-dose radiation therapy delays the growth of adenomatous nodules by decreasing the ability of the thyroid gland to respond to stimulation. In conclusion, thyroid nodules appear to arise less frequently after high-dose radiation in the region of the head and neck for Hodgkin's and non-Hodgkin's lymphomas than after low-dose radiation of the same area for benign conditions.

Health aspects, Hodgkin's disease, Non-Hodgkin's lymphomas, Lymph nodes, Thyroid gland

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