Cancer-predictive tests

The radiobiological arguments discussed above indicate that the high-LET radiation could bring a benefit in the treatment of some cancer types. However, they also imply the need for the development of predictive tests, allowing the radiation oncologist to... 

Human cancers 1. Test predictions Microsatellite instability in nontumoral tissues... 

Neither DRE nor PSA is sensitive or specific enough to be used alone as a screening test.12 Although the relative predictability of DRE and PSA is similar, the tumors identified by each method are different. Catalona and associates13 confirmed that the combination of a DRE and a PSA determination is a better method of detecting prostate cancer than DRE alone. 

Evaluation of CA 125 tests has shown moderate sensitivity, higher specificity, and predictive values in ovarian cancer patients when determining the presence of an intraperitoneal tumor or future occurrence at the time of second-look procedures. Studies have shown that the CA 125 level obtained at the time of a second-look procedure correlates reasonably well with the size of the tumor. As mentioned before, the predictive value of a marker depends on the prevalence of a particular type of malignancy in the intended population. Thus, evaluating a marker s diagnostic potential must be based on prevalence in a well-defined group for results to be generally applicable (i.e., prevalence of ovarian cancer in women with pelvic masses). 

From Assumption C and Eq. (l), the distribution of Mr is accurately known. From statistics on lung cancer mortality, the distribution of M is accurately known. Thus, the distribution of Mr can be calculated mathematically, and the problem is completely solved, allowing us to derive predictions that can be tested. In particular,... 

The amount of particles determine the quantity of decay products that stay in the air (equilibrium fraction, F) and the fraction of activity associated with the "unattached or ultrafine mode of the size distribution (fDot) These decay products are certainly harmful at high concentrations but we cannot yet detect the effects at normal levels because the vast majority of lung cancer death are due to smoking. Models predict that potentially 9000 lung cancer deaths per year in the United States are due to indoor radon. Methods are currently available and new methods are being developed and tested for lowering the levels of radon in indoor air. 

McCann, J. Ames, B. "The Salmonella/Microsome Mutagenicity Test Predictive Value for Animal Carcinogenicity " in "Origins of Human Cancer " Hiatt, H. H., Watson, J. D., Winsten, J. A., Eds., Cold Springs Harbor Laboratory Cold Springs Harbor, New York, 1977, pp. 1431-50. 

A review of data from 250 chemicals found an 82% concordance between results of carcinogenicity testing in the mouse and the rat (Purchase, 1980). Haseman et al. (1984a) reported a concordance of 73% for 60 compounds studies in both species. However, 30 to 40% of 186 National Cancer Institute (NCI) chemicals were found to be positive in one species and negative in the other (Gold et al., 1984). It is reasonable to conclude that neither rodent species will always predict the results in the other rodent species or in humans, and that the use of two species will continue until we have a much better understanding of the mechanisms of carcinogenesis. 

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