WHY RADIATION AFFECTS CANCER CELLS MORE THAN NORMAL CELLS – GREATER PROPORTION OF DIVIDING CELLS (PART 1)
Let’s now see what makes cancer cells more likely to be killed by radiation than normal cells. Firstly, the part of the cell that is most sensitive to radiation is the part that controls reproduction. This means that tissues with a high proportion of cells that divide frequently show the harmful effects of radiation more obviously and more quickly than tissues in which the cells rarely divide. Cells that are actually in the process of dividing when radiation passes through them are so sensitive to its harmful effects that they die within a few hours. Cells which are not actually dividing at the time of treatment still suffer serious damage to their reproductive ability. They can often continue to function quite normally provided they don’t try to divide. Once they do, it is likely that they will die in the attempt. Most cancers have a higher proportion of cells that divide regularly than most normal tissues. Most, but not all, cancers are therefore likely to show more rapid and severe damage after radiation than most, but not all, normal tissues.
Low doses of radiation interfere with the ability of the cell to divide. Higher doses kill cells directly. Therefore any cell can be killed by radiation if the dose is high enough.
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