The great variety of cancers reflects the fundamental mechanism by which the disease arises: the different combinations of genetic variations that cause normal cells to grow excessively and behave badly. These cancer-causing mutations may be inherited or, more commonly, incurred after birth, and our ability to describe them offers entry to a world in which cancer can be better controlled. We already know a few hundred of the genes that are mutated in various cancers, and we are poised to discover virtually all of them through a new kind of “genome project” that is just beginning.
An obvious application of genetic knowledge about specific cancers is the development of drugs and antibodies that reverse the effects of the mutations in those cancers. Some success in this difficult endeavor has already been achieved — in the clinic, not just the laboratory. But new genetic knowledge can also be used to assess an individual’s inherited risk of developing certain kinds of cancer or to predict the likely behavior of any identified tumor.
Hereditary risks of developing cancer can now be determined by examining about 30 different genes that can cause changes associated with certain cancers. This information can be enormously beneficial by encouraging early screening or preventive surgery. But it can also create anxieties about genetic discrimination, upset families and raise disturbing questions about who should be tested and when. Most of the known mutations are so uncommon in the population and so expensive to find by DNA testing that it is not yet justified to examine people who aren’t from cancer-prone families.
Moreover, depending on the mutant gene, the risks that it will actually cause cancer can vary, from slightly above average to nearly 100 percent. And the absence of an inherited mutation, while reducing risk, does not preclude the cancer. In addition, there are doubtless more inherited variant genes to be discovered, especially variants that confer relatively weak risks of cancer. These features complicate genetic assessment of cancer risk, but I believe that the approach, on balance, can benefit affected individuals and public health.
These predictions will be especially important when tumors are found at very early stages. While not yet perfect, such tests are welcome harbingers of a more rational basis for making crucial decisions about treatment.
An obvious application of genetic knowledge about specific cancers is the development of drugs and antibodies that reverse the effects of the mutations in those cancers. Some success in this difficult endeavor has already been achieved — in the clinic, not just the laboratory. But new genetic knowledge can also be used to assess an individual’s inherited risk of developing certain kinds of cancer or to predict the likely behavior of any identified tumor.
Hereditary risks of developing cancer can now be determined by examining about 30 different genes that can cause changes associated with certain cancers. This information can be enormously beneficial by encouraging early screening or preventive surgery. But it can also create anxieties about genetic discrimination, upset families and raise disturbing questions about who should be tested and when. Most of the known mutations are so uncommon in the population and so expensive to find by DNA testing that it is not yet justified to examine people who aren’t from cancer-prone families.
Moreover, depending on the mutant gene, the risks that it will actually cause cancer can vary, from slightly above average to nearly 100 percent. And the absence of an inherited mutation, while reducing risk, does not preclude the cancer. In addition, there are doubtless more inherited variant genes to be discovered, especially variants that confer relatively weak risks of cancer. These features complicate genetic assessment of cancer risk, but I believe that the approach, on balance, can benefit affected individuals and public health.
These predictions will be especially important when tumors are found at very early stages. While not yet perfect, such tests are welcome harbingers of a more rational basis for making crucial decisions about treatment.
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