Cancer is not one disease but many, and some of the differences were highlighted in two recent newspaper stories.
The first article described the change in death rates and the number of new cases of different types of cancer over the decade ending in 2003. The most common forms are lung and colorectal cancer in men and women, prostate cancer in men, and breast cancer in women.
The good news is that death rates from each of these cancers, except for lung cancer in women, declined significantly during the 10 years ending in 2003. The rate of decline in death rates was 1.6 percent per year for men, but only half as much for women. The improvement among men was attributed mainly to their reduced use of tobacco. The authors of the article observe that more effort is required to get women to stop smoking.
Despite this overall decline in death rates from cancer, there was no overall change in the rates of new cancers diagnosed, and a small increase in lung cancer rates among women. The most dramatic rise was in the rate of thyroid cancers among women, including a 9 percent increase between 2000 and 2003.
Fortunately, thyroid cancer affects only about 30,000 people each year, compared with the annual diagnosis of more than 210,000 cases of breast cancer and 145,000 cases of colorectal cancer. The higher rate of thyroid cancer is mostly due to better diagnostic tools. Although most types of thyroid cancer can be treated effectively, some forms are always fatal.
The second article I read reported on progress identifying the genes responsible for breast and colorectal cancers. Here, again, there are differences. Researchers have found 122 different cancer-causing genes in breast cancer and 69 in colorectal cancer, with almost no genes in common between these two types of cancer.
Even more surprising, cancerous tumors from the same organ had only about 5 genes in common. This is important because, with few exceptions, cancer treatment options available today are nearly identical for all people suffering from the same type of cancer.
Much more work remains to be done to improve our knowledge of the genetic differences among cancers. The hope is that identification of these and other cancer-causing genes will make it possible to design unique treatments for individual patients that target the specific abnormal genes found in their cancers.
