For one searing day this week I thought I had cancer. As it turns out, I don’t, at least not yet. In the days since, I have been thinking a lot about cancer. I am at that disturbing age — the mid-fifties — where my friends are beginning to fall victim to cancer’s cruel summons, and this week for a few short hours I tasted the bleak mixture of threat and hope that these friends have had to live with every day.
So I set out to see how the battle against cancer is going. Like everyone these days, I went to the internet. The National Cancer Institute’s comprehensive data base at www-seer.ims.nci.nih.gov provides as complete a picture as anyone can digest.
I found that the news in general is encouraging. The incidence of many types of cancer has leveled off or even dropped. However, as I plowed through the sea of numbers, I bumped up against one battle, the fight against non-Hodgkin’s lymphoma, which is not going at all well. This deadly cancer, for which there is no household word, is becoming more common, for no apparent reason.
A lymphoma is a cancer of the lymph tissues found throughout the body that store and transport the white blood cells which defend you from infection. There are two kinds of lymphoma, Hodgkin’s lymphoma and a collection of some 30 other cancers that are collectively called non-Hodgkin’s lymphomas. Some of the non-Hodgkin’s lymphomas are slow-growing and allow patients to survive many years. Others are highly aggressive and rapidly fatal.
No one knows exactly what causes either kind of lymphoma, although both seem associated with weakened immune systems, and non-Hodgkin’s lymphoma has been linked to a virus called HTLV-1 (human T-cell lymphoma virus). For some reason, American farmers have for decades exceeded the national average for non-Hodgkin’s lymphoma, suggesting that herbicides, pesticides, and other agricultural chemicals may be a risk factor.
While public attention in the last decades has been focused on lung, breast, and colon cancer, the number of non-Hodgkin’s lymphoma cancer deaths have been increasing steadily. In 1962, 7,423 Americans died of non-Hodgkin’s lymphoma. Every year since, the numbers have grown. This year the American Cancer Society estimates the number of cancer deaths attributable to non-Hodgkin’s lymphoma will be 26,100. That’s almost four times as many deaths as in 1962!
This year some 62,300 Americans will be diagnosed with lymphoma (about 7,400 with the often curable Hodgkin’s variety). There is no early-detection test, and doctors can offer no advice on preventing it. But there is good news. A variety of immunotherapy agents are coming onto line that seem particularly effective against lymphomas. While the term “immunotherapy agent” is a mouthful, the idea behind it is simple. Your body contains many millions of cells called B cells that are little factories for making the antibodies that defend you against infection. Each one of these B cells makes its own unique kind of antibody. Because there are so many different kinds of antibody being produced, there is always likely to be at least one that gets the job done, no matter who the invader.
Sifting carefully through these billions of cells, gene engineers have found a few that target lymphomas. Using the tricks of their trade, they have isolated these cells in pure culture. Each established culture is composed of cells churning out antibody specifically targeted against a particular lymphoma. Gene engineers call the highly specific antibodies produced by this kind of cell culture “monoclonal antibodies.”
Monoclonal antibodies directed against specific lymphomas have great promise as therapeutic agents. They seek out cells that match their 3D shape, and only cancer cells do. When they find a cancer cell, they attach to it, alerting the immune system to kill that cell.
One of these immunotherapy agents, called Rituxan, is already sold. It targets non-Hodgkin’s lymphoma cells that carry a surface protein called CD20. Still being tested are monoclonal antibodies targeted at lymphomas carrying CD22, CD25, and CD30 surface proteins. These promise future treatment of many kinds of non-Hodgkin’s lymphoma.
An experimental souped-up version of lymphoma monoclonal antibody called Bexxar carries radioactive iodine. Lymphoma cells to which it attaches are zapped with radiation without waiting for the immune system to get around to removing them. This promising treatment is still experimental and not yet generally available, although initial results are very promising and government approval seems likely.
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