Screening for lung cancer: a critique of the Mayo Lung Project
Article Abstract:
Lung cancer accounts for nearly six percent of all deaths in the United States. By far the most important risk factor is cigarette smoking, which not only contributes to the development of lung cancer, but tends to obscure the earliest symptoms, so that by the time the patient seeks medical care, the disease is already incurable. Clinical evidence suggests that the detection of early lung cancer in its asymptomatic stages would provide better chances for survival. However, it does not automatically follow that screening for lung cancer will lead to improved survival. For example, it must be demonstrated that the screening program will detect a significant proportion of cancers in the earliest stages. Furthermore, a screening program must be economical, and the cost and distress associated with false positive results must be minimized. Several major trials have been conducted to determine if regular screening for lung cancer using chest X-rays and/or sputum examination is practical. These major trials were established by the National Cancer Institute and conducted at Johns Hopkins University, Memorial Sloan-Kettering Cancer Center, and the Mayo Clinic. The authors review the results of the study, which involved 9,211 men, all heavy smokers, who were followed for over a decade. X-ray and sputum cytological screening examinations were performed for 4,618 men, while the control group of 4,593 men were advised to have yearly X-rays, but were not reminded or prompted to participate in screening. The subjects were, of course, contacted annually to determine their health status. Surveillance of nearly 38,000 person-years in each group was accumulated. In the group receiving regular check-ups, the rate of lung cancer detection was significantly better, the cancers were more likely to be detected at a stage when surgery was still possible, and the length of survival was longer. However, the patients still died of lung cancer, and there were no significant differences between the two groups in overall mortality from lung cancer. The results suggest that mass screenings for lung cancer, at least at this time, are not warranted. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: Cancer
Subject: Health
ISSN: 0008-543X
Year: 1991
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Abnormal vitamin B6 status in childhood leukemia
Article Abstract:
While many studies have investigated the overall nutritional status of children with cancer, the status with regard to vitamin B6 has not been investigated. Vitamin B6 is an important factor in over 100 different chemical reactions within cells. It has been hypothesized by some that abnormalities in vitamin B6 metabolism could play a role in the development of cancer. For this reason, the vitamin B6 status was investigated in 37 children with leukemia and in 37 age-matched controls. The study examined the plasma levels of pyridoxal 5'-phosphate (PLP), which is the biologically active form of the vitamin; it is generally believed that the circulating plasma levels of this vitamin are a fair indication of the total body store. It was found that the patients generally had significantly lower levels of PLP than the control subjects, although not all the leukemia patients were below the normal range. However, a low level of a vitamin in a cancer patient does not mean that a low level contributed to the development of the disease. While some experiments in animals have indicated that vitamin B6 deprivation can contribute to the development of cancer, there is no reason to think that the children studied in the present research were deprived prior to the development of their disease. Testing of the siblings of these patients did not reveal any abnormalities, and it seems likely that the depressed levels of vitamin B6 observed in these patients are a result of inadequate nutrition resulting from cancer, rather than a contributing cause. However, it cannot be ruled out that at least some of the observed reduction in circulating vitamin B6 may result from the increased use of the vitamin by the leukemic cells themselves. Therefore, the possibility that any supplementation of the diets of these children with vitamin B6 may actually provide the cancer cells with more of what they need to grow must be considered. More must be learned about the metabolism of vitamin B6 in leukemic children before guidelines for vitamin supplementation are developed. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: Cancer
Subject: Health
ISSN: 0008-543X
Year: 1990
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