Biology of cancer and aging

Article Abstract:

There can be no doubt that the risk of cancer increases with age. However, little is known about the physiological reasons for this effect. There have been many suggested explanations; none of the explanations excludes some contribution of the others. One possibility is that the age-related increase in cancer simply results from having been exposed to cancer-causing agents for a greater period of time. The aging of the immune system might permit the progression of cancers that would have been successfully eliminated in the younger years. Some researchers have suggested that age-related metabolic changes may make older people more susceptible to cancer-causing agents, while others suggest that the long period of time required for a cancer to develop makes it a disease of older people. One intriguing possibility is that as people age, the ability of their cells to repair DNA damage declines; this effect may contribute both to the effects of aging and to the increased likelihood of cancer. It is clear in animal studies that the development of cancer is affected by the age of the host. Cancer cells may be directly implanted into laboratory rats. Some cancer cells, such as melanoma, grow more slowly when transplanted into older rats. Other cancer cells, such as fibrosarcoma, grow more rapidly in older animals. These results suggest that the relation of aging to the development of cancer is not likely to be explained by any single, simple rule. Curiously, estimates of human aging indicate that if cancer were completely eliminated as a cause of death, the average human life span would increase by only five percent, or less than four years. In this light, it is interesting to note that experimental control of the diets of laboratory animals can increase their life span by more than 35 percent, which would be over 25 years in human terms, if the same proportion applied. Unfortunately, little is known about the physiological aspects of aging or how they relate to the increased risk of cancer. (Consumer Summary produced by Reliance Medical Information, Inc.)

Aging, Physiological aspects, Development and progression

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Rural-urban differences in stage at diagnosis: possible relationship to cancer screening

Article Abstract:

Urban residents have higher rates of cancer and higher mortalities from cancer than residents of rural areas. However, research has now demonstrated that the differences in health care availability and access to cancer screening programs seem to be contributing to an excess of advanced cancers among rural residents. The study, which took place in Atlanta, Georgia and surrounding rural areas, found a relative excess of advanced cancer of 21 percent for whites living in rural areas. Among rural blacks, the excess was even greater at 37 percent. The review of medical records also found that 18.3 percent of the rural case records did not report a stage at all, in contrast with 9.6 percent of the records from the urban areas. One reason why a stage might not have been determined is that an advanced cancer case might be considered inoperable, and thus, surgical staging information was never obtained. It seems likely that the excess of advanced stage cancer in rural areas is even greater than the figures would seem to indicate. The five-county Atlanta metropolitan area has 17 approved cancer programs or clinics; there are none in the surrounding 10 rural counties. There are 39 certified oncologists practicing in the metropolitan area; there are none in the surrounding 10 rural counties. The differences are most obvious for cancers such as breast cancer and cervical cancer for which effective screening programs exist and for which early detection has a demonstrable benefit. However, one rural-urban difference that was not adequately explained was a great excess of advanced prostate cancer among rural residents, which was limited to blacks. For both rural and urban whites, about 70 percent of the cases were detected in the early stages. While urban blacks had a roughly comparable chance of having early prostate cancer detected (63 percent), prostate cancer was detected while still localized in only 37 percent of the rural blacks. (Consumer Summary produced by Reliance Medical Information, Inc.)

Health aspects, Georgia, Atlanta, Georgia, Medical examination, Demographic surveys, Periodic health examinations

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