Prediction Of Radiosensitivity Research Articles

Prediction of Tumor Radiosensitivity by Hexafluoromisonidazole Retention Monitored by [1H]/[19F] Magnetic Resonance Spectroscopy

Hexafluoromisonidazole (CCI-103F) is a hypoxic cell label that can be measured by in vivo [1H]/[19F] magnetic resonance spectroscopy (MRS). The retention of CCI-103F in SCCVII tumors was found to be correlated with tumor size, with larger tumors retaining more label. Such a correlation was anticipated, as larger SCCVII tumors have larger hypoxic fractions. A significant but less strong correlation was also found between CCI-103F retention and the fraction of tumor cells surviving after 10 Gy irradiation, with tumors that retained larger amounts of CCI-103F having higher surviving fractions. These results indicated that non-invasive MRS measurement of CCI-103F retention could predict radiosensitivity in SCCVII tumors. The lack of a strong correlation between CCI-103F retention and radiosensitivity, however, indicated that hypoxic fraction was not the only factor influencing radiosensitivity in these tumors.

Radiation Response Characteristics of Human Cells in Vitro

Improvements in tissue culture techniques and growth media have made it possible to culture a range of cells of human origin, both normal and malignant. The most recent addition to the list are endothelial cells from umbilical cord veins. Interesting results in radiosensitivity studies of these human cells have been obtained, some of which may have implications in radiation therapy. (i) Repair of potentially lethal damage (PLDR) has been observed in all cell lines investigated; cells of normal origin repair PLD at least as well as malignant cells, which makes clinical trials of PLDR inhibitors of doubtful usefulness. (ii) No apparent correlation can be made between the extent of PLDR and the traditional radioresponsiveness of a particular tumor type. Indeed, if anything, it could appear to have an inverse correlation since the most resistant tumor cells show the smallest amount of PLD repair. (iii) Dose-rate effects appear to be better predictors of radiosensitivity than PLDR capacity. (iv) Sublethal damage repair, manifest by a dose-rate effect, has also been observed in all human cell lines tested. Cells of normal tissue origin, including fibroblasts and endothelial cells, exhibit a dose-rate effect that is intermediate between that for cells from traditionally resistant tumors (melanoma and osteosarcoma) and cells from more sensitive tumors (neuroblastoma and breast).

Prediction of Radiosensitivity of a Mouse from Its Physiological Characteristics before X-Irradiation

The animals used were 143 female mice, which were housed individually in metabolism cages. Their physiological characteristics were studied from the 8th week of age for 10 days. During this period of observation the mice were deprived of laboratory chow for 2 days. On the 11th day after the period of the observation they were subjected to a total-body x irradiation with 660 rad, which resulted in LD/sub 45/(/sub 30/). Nineteen parameters, adopted as indicators of physiological characteristics of individual animals, were calculated from the daily changes in body weight, water consumption, urine volume, and the amount of urinary 5-hydroxyindoleacetic acid. When tested with their mean values none of these parameters showed a statistically significant difference between the survivors and the decedents, whereas by the method of quantification of Hayashi (a multidimensional analysis on these parameters), it was possible to predict the deaths of individual mice with a high rate of success. (auth)

Observations on the capillary vascular pattern in ovarian tumors

The azo-alkaline phosphatase method was used for the histochemical demonstration of the capillary vascular pattern in thick, frozen sections of fresh specimens of 8 normal ovaries and 36 ovarian tumors. The possible value of the method in the diagnosis of malignancy in borderline cases and in the prediction of radiosensitivity is discussed.

Cytological prediction of radiosensitivity in carcinoma of the cervix.

Summary:1. A study of sensitization response (SR) and radiation reaction (RR) values in carcinoma of the cervix has been conducted with special reference to the use of these indices to select those patients most likely to benefit from post‐irradiational surgery.2. SR studies did not prove to be a reliable prognostic index. In particular, no valid association could be demonstrated between SR value and the incidence of local residual growth or pelvic lymph node metastasis.3. RR studies revealed a significant correlation between RR value and the presence of local residual growth after previous radiotherapy. This finding can be used as an aid in selecting those patients who would best benefit from subsequent radical surgery.4. The drawbacks involved in RR evaluation lie chiefly in the technical difficulties of reading, in its limited use with small and superficial Stage I growths, and its failure to help detect the presence of nodal metastasis.5. Determination of the correct treatment of carcinoma of the cervix is a complex and highly individual problem. Before a decision is made, every available facet of prognostic aid should be considered.

Prediction of the sensitivity of plants to chronic gamma irradiation

The principal site of damage to plants by ionizing radiation is the cell nucleus. The effect on plant growth, measured as size or weight, used as the criterion of sensiviti to chronic gamma irradiation, shows the variation in sensitivity between different species of higher plants to approach 500-fold. This variation is correlated with chromosomal and nuclear characteristics: that is, plants which have low chromosome numbers and large nuclear volumes are most sensitive while polyploids and plants with high chromosome numbers and small nuclear volumes are highly resistant. The rate of nuclear division is also important. A slow rate increases the exposure time of each interphase nucleus to chronic irradiation and thereby increases the nuclear damage. Any environmental factor which influences the rate of growth will by influencing the rate of cell division, affect sensitivity. Environmental factors influencing the degree of response caused by ionizing radiation fall into four general categories: (1) those modifying dosage, dose rate or dose fractionation; (2) those involving type of ionizing radiation; (3) those influencing growth rate or rate of cell division; and (4) those affecting recovery from radiation damage. Consideration of these nuclear and environmental factors permits the prediction of radiosensitivity of plant species not previously irradiated. At the plant population level, chronic irradiation can probably be expected to have its most severe effects on sexual reproduction because during and after meiosis: (1) nuclear volume is high; (2) chromosome number is reduced after meiosis; (3) the rate of nuclear division may be low, some species requiring 2 years between meiosis and full maturation of seeds; (4) meiotic pairing and reduction tend to enhance the damage wrought by aberrations which may survive in diploid somatic cells. The high sensitivity of sexual reproduction is probably further enhanced by seed dormancy, during which damage accumulates. The relative dosage levels necessary to produce specified responses in growth rate, reproductive capacity or in degree of mortality vary greatly within a species. Both vegetative growth and the integrity of the sexual reproductive process of pines appear to be highly susceptible to damage from ionizing radiation and the genus Pinus includes some of the most radiosensitive plants known. Chronic exposures averaging about 8 months per year for 9 years produced detectable effects on growth of P. rigida at average dose rates as low as 2 r/day. The lethal acute dose for P. strobus seedlings of 600 r also indicates a high radiosensitivity. The principal reasons for these high sensitivities are the large nuclear volume of pines and, for chronic exposures, the long period between production of the meiocytes and the maturation of seed. It is predicted that many other gymnosperms will have a radiosensitivity approaching that of pines. A comparison of the estimated maximum exposure of vegetation from fallout occurring in New York City in 1958 with the minimum chronic radiation levels known to influence growth and reproduction of Pinus rigida indicates that these levels of fallout are approximately 1/800th of the 2 r/day necessary to produce visible morphological effects within several years. A forest stand representative of the Long Island oak-pine forest is currently being irradiated with chronic gamma radiation from about 9500 c of cesium-137 in an effort to provide quantitative estimates of radiation effects at the population and community levels. Present information makes possible the prediction, on the basis of nuclear characteristics, that the first year's exposure will cause selective killing. All trees within 35 m of the source (85 r/day) will die leaving a shrub community dominated by Gaylussacia baccata, probably one of the most resistant of the species present. The pitch pine ( Pinus rigida), with its large nuclear volume, is the most sensitive plant present and will probably be killed by the second year at distances up to 75 m (15 r/day). This radiation facility is available to research workers interested in the general problem of radiation effects on organisms.